Northwest Dragonflier

Seeing Red: Cardinal Meadowhawk

2012-02-20T12:53:00.000-08:00

Most meadowhawks (Sympetrum) are red—at least the males are, and sometimes the females too—but the Cardinal Meadowhawk (S. illotum) is about as red as they get. Mature males are simply vivid. Among the first spring-flying dragonflies in the Pacific Northwest lowlands west of the Cascades, it’s a welcome splash of color after a damp, dreary winter. Look for them at marshes and well-vegetated ponds and lakes of all sizes. Check out this map at OdonataCentral and see if this species has been recorded in your area.

They are also pretty easy to identify between the abdomen lacking any black patterning (which I think amplifies the redness), the red face, the brown thorax with a pair of white spots on the side, and wings with short basal black streaks enveloped in an amber suffusion and bright saffron veins along the leading edge. Females are either brownish or reddish in color, but either way they have the same white spots on the thorax and the short black streaks at the wing bases—a unique character among our meadowhawks.

Female Cardinal Meadowhawk (Sympetrum illotum). Notice the pair of white spots on the thorax and the short black streaks at the wing bases.

In the Pacific Northwest, we have several weeks yet before we can reasonably expect to see Cardinal Meadowhawks (or any adult dragonflies for that matter), but keep an eye out for them on those pleasantly warm, sunny, t-shirt appropriate days in April and early May (earlier further south)—weather permitting, of course!

A Checklist of North American Odonata, 2012

2012-02-17T14:38:00.000-08:00

Click image to open the PDF.

Just a quick message to let you know that the 2012 edition of A Checklist of North American Odonata by Dennis Paulson and Sidney Dunkle is now available. You can find the PDF (just over 1 MB) here at OdonataCentral.org. You can also just click on the image at right to open it.

Originally published by the Slater Museum of Natural History, University of Puget Sound, in 1999, this document isn’t simply a list since it contains a wealth of information on each species recorded from the continental United States and Canada. In each species entry you can find reference information for the original description, the type locality, etymology of the scientific and English names, and a brief description of its range. Similar information is also presented for each genus.

A sample from A Checklist of North American Odonata, 2012 edition.

The introduction has information on the number of species and genera in each family and suborder, the number of newly described species by family and by decade, and on the adoption of standardized English names. At the other end of the document, the extensive annotated bibliography indicates which genera and species were described in each publication, and the appendix wraps it up with a list of synonyms.

If you’re serious (even just mildly serious) about Odonata in North America, this document is a must-have, and since it’s free, you can’t argue about the price!

The Rest of the Story

2012-01-30T17:05:00.000-08:00

A picture is worth a thousand words, as the saying goes, but that doesn’t mean that there aren’t many more words lurking behind the photo which tell a much more interesting story.

What do you see in the photo above? The primary subject is a dragonfly—a female Grappletail (Octogomphus specularis) to be exact, a species of clubtail in the family Gomphidae. What is the slender blue “stick” that this Grappletail is grappling? That is the abdomen of a male Vivid Dancer (Argia vivida)—a damselfly, his head and thorax in the dragonfly’s digestive tract by the time this photo was exposed. Odonate-on-odonate predation is always interesting when you see it, but not so uncommon that it’s ever a surprise—especially in cases like this when the predator is significantly bigger than the prey.

That photo was taken at Gold Lake in the central Oregon Cascades—a special place for a number of reasons. One of them is the large numbers of Grappletails that congregate where the waters flow out of the lake and become Salt Creek. Dozens and dozens of them can be seen sitting all over the place—on boulders, on logs, on the bridge over the creek, on the surrounding vegetation, and on you. I have photos of up to 13 of them perching on a single boulder. It is really odd to see so many individuals of any clubtail (or any dragonfly species, for that matter) together at one place. It’s also a very enjoyable place for photography since there is at least one Grappletail everywhere you look, and they are often very approachable.

Here's a better view of a different female Grappletail (Octogomphus specularis) at Gold Lake.

During a Gold Lake visit in August of 2007, I was trying to photograph a female Grappletail that was sitting on a log, but as I was looking through my camera’s view finder, a blue blur kept buzzing her head and she flew up each time to chase the annoying meddler away. This wasn’t working out for me, so I lowered my camera to see what was going on. The intruder was a damselfly—a male Vivid Dancer (Argia vivida). What was he doing? Well, I couldn’t be positive, but it sure looked to me like the little guy was trying to go into tandem with the relatively gargantuan Grappletail (with the ultimate goal of copulating, presumably). I guess he had a fondness for Amazons.

I know, I know, this seems pretty fantastic, but each time the damsel dropped down, he curved his abdomen forward as though he intended to clasp her behind the head with his abdominal appendages. I can’t imagine what else could have possibly motivated him to do such a thing. The mere notion that a damselfly would even attempt to go into tandem with a dragonfly—one twice his length, really blows my mind. It’s unheard of as far as I know. Assuming that I correctly assessed the dancer’s intentions (I concede that I could be wrong, but I can’t imagine what else was going on), it raises some interesting questions such as, Can a damselfly really know whether a dragonfly is a male or female, and if so, how?


An intact male Vivid Dancer (Argia vivida) wisely copulating with a female of his own size.

It’s funny to think about what it would have looked like if he was successful, if she was receptive, and they actually got tab A into slot B. Take a look at the copulating pair of Vivid Dancers at right, and just try to imagine that the female (the non-blue one) is a dragonfly about twice as long as the male and quite a bit chunkier. Completing that circle would put some serious stresses on the joints!

Naturally, the Grappletail was having none of it! She chased the little dancer away four or five times, returning to her log after each flight. Unfortunately for him, he made one too many attempts. The last time he dropped down, she flew up, chased him, grabbed him in mid-air, and perched in streamside trees to make a meal of the little love-struck damsel. That was when I snapped the photo at top, and that’s the rest of the story.

Mite-y Dragons: Odonata and Water Mites

2012-01-22T18:53:00.000-08:00

If you look at odonates often enough, closely enough, you’re bound to notice some that areaccessorized with tiny orbs—often orangish or reddish in color, clinging tovarious parts of the body like jewelry. But it isn’t “bling” or the latest fadin body art. When I first started catching odonates and looking at themin-hand, I thought they might be eggs which got stuck to the body, but thatisn’t right either. What are these sanguine spheroids, these rusty rondures, theseblushing bulbous globules?

Male Tule Bluet (Enallagma carunculatum) with a string of mites under the abdomen.

These are ectoparasites—meaning that the host–parasite interaction occurs onthe outer surface of the host rather than internally. More specifically, theseare larval water mites or Hydrachnida, which are in the same class ofarthropods as spiders, scorpions, ticks, and their colleagues. Water mitesthat use odonates as hosts are predominantly species of Arrenurusin the family Arrenuridae—of which at least 55 species have been described asectoparasites of Odonata so far.


Top: Male Alkali Bluet (Enallagma clausum) with a couple of mites tucked under the thorax between the middle and hind legs. Do you see them? Bottom: Male Pacific Forktail (Ischnura cervula) with a single mite on his "shoulder" above the base of the middle leg.

Water mites that are attached to an adult odonate actually initiatedtheir relationship underwater during the odonate’s nymph stage. Thefree-swimming larval mites find final instar odonate nymphs and cling to them,but they are not parasitic at this point—they just try to find a place on thebody where they can hang on and avoid being knocked off when the nymph groomsitself (under the wing pads, for example). It would be interesting to know howthe mites determine which odonates are nearing emergence and which are not.When the odonate emergesfrom the water to become an adult, the mites crawl from the exuvia (the shednymphal skin) onto the just emerged adult (which is probably still goingthrough the process of expanding its abdomen and wings), and attaches somewhereon the body while the exoskeleton is still soft and easy to pierce. The mites most often attach to the ventral areas of the thorax or abdomen. Rarely you see them higher on a dorsal surface or on the head, and they sometimes even attach to the major wing veins although I’ve never seen this myself. Apparently attachment site preference varies by mite species.

Finding a meal isn’t the only objective for the mites. They want to traveltoo. The technical term for this is phoresy—the use of one animal byanother for transportation. Lots of mites are phoretic, at least during some stage of their life cycle, and they use avariety of arthropods and other animals for transport. Why do mites want to travel? There are anumber of potential benefits of dispersal among which are finding food (orhosts), finding habitat, expanding the species’ range, and increasing geneticvariation by reproducing with individuals from other populations.

Male Eight-spotted Skimmer (Libellula forensis) with a number of mites on the thorax and one on his head below the eye.

Eventually the odonate host returns to wetland to reproduce (this may be theplace where it emerged or it may be someplace else). When this occurs, theirhydrachnid passengers—fully engorged and significantly bigger than when theyfirst found their host, have their opportunity to unplug and take a triplegainer into the water where they can continue their life cycle. So theparasitic use of adult odonates by water mites is temporary.

Although odonates carrying water mites typically appear to be healthy andenergetic, studies indicate that their longevity, flying endurance, and reproductive success canbe negatively impacted by the stowaways. This seems to be especially true whenlots of mites cluster together and cause significant damage to the cuticle ofthe exoskeleton, perhaps leading to desiccation. I assume that clusters of mitesat particular locations on the odonate body—until they drop off anyway—can also interfere withreproduction by impeding copulation or by blocking sperm transference to themale’s secondary genitalia. It seems that just a few mites attached to unobtrusive areas ofthe body have negligible impact, and it’s more of a commensal relationship inthat case.

Left: Female Lyre-tipped Spreadwing (Lestes unguiculatus) with several mites on the thorax and another about halfway down the abdomen. Right: Male Spotted Spreadwing (L. congener) with a cluster of mites near the tip of the abdomen and another single about halfway up. I can't see how the male can transfer sperm to his secondary genitalia with all those mites there.

It’s interesting to consider which odonates are frequent water mite hostsand which are not. Water mites occur primarily in non-flowing (lentic) orslow-flowing waters, so naturally, odonates which prefer those habitats are good candidates. In general damselflies (Zygoptera) seem to hostwater mites more often than dragonflies (Anisoptera); however certaindragonflies in the skimmer family (Libellulidae) are parasitized regularly andthese include the pondhawks (Erythemis), whitefaces (Leucorrhinia),king skimmers (Libellula), and meadowhawks (Sympetrum). On theother hand, some other groups of dragonflies—for example darners (Aeshnidae),occur in lentic habitats too, but they rarely host water mites. Are the mitesdiscriminating or are these dragonflies somehow mite-resistant? I don’t know.Maybe the nymphs of these dragonflies are more skilled at evicting stowawaysbefore emergence.

Left: Male Striped Meadowhawk (Sympetrum pallipes) with a number of mites on the thorax. Right: Female Band-winged Meadowhawk (S. semicinctum) very heavily infested with mites. This is one of the worst cases that I've ever seen and it can't be good for the host.

So keep an eye out for odonates carrying these little hitchhikers and thinkabout how far they may have traveled and how far they still have to go beforethey dive into a pond. At least they get a meal with their flight which is morethan I can say for my flying experience lately!

Further Reading

Some of the information I present here was gleaned from Philip Corbet’smonumental Dragonflies: Behavior and Ecology of Odonata published in1999. I recommend that you start here if you’d like to read more about thistopic (or pretty much anything having to do with odonates). Every time I crack open this tome I learn something new.

I also found an online PDF of a 2006 paper by Andrzej Zawal on the use of odonates by Arrenurus larvae at a lake in Poland, and this indicates that odonate nymphs are sometimes parasitized by mites too. You can find that PDF here. Perhaps some species of mites are parasitic on odonate nymphs and others are strictly phoretic until the odonate emerges.

Protoneura: Sparks in the Dark

2012-01-15T16:28:00.000-08:00

Considering that it’s January and that I can’t reasonably expect to see an adult odonate for a couple of months in the damp, chilly Pacific Northwest, I thought I’d take you back to Ecuador to profile one my my favorite genera of damselflies.

The Protoneura (21 known species) are small, but relatively long, skinny damselflies in the family Protoneuridae—the “threadtails” as they are known commonly. This is a mostly tropical family found circumequatorially, but three species make it as far north as southern Texas. Male Protoneura are often brightly colored, at least on the thorax, but they also stick to shady areas along forested streams where they can be difficult to spot. It’s not unusual to notice a bit of bright color suspended over a small stream, then realize that it’s part of a Protoneura hovering motionlessly.

Below are the four species of Protoneura that I have photographed in Ecuador. Two of them (scintilla and woytkowskii) were in the Amazonian lowlands and the other two (macintyrei and amatoria) were in the Pacific lowlands.

Male Protoneura scintilla in Sucumbíos Province, Ecuador. A rather dark species overall except for the orange "flames" on the thorax.

Male Protoneura woytkowskii in Sucumbíos Province, Ecuador. A lot more orange color on this one extending onto the tops of the eyes and the legs, as well as a bit near the tip of the abdomen. The hovering Protoneura at the top of this post is also this species.

Male Protoneura macintyrei in Los Ríos Province, Ecuador. Similar to woytkowskii above, but note the difference in thorax pattern and eye color.

And now my favorite...

Male Protoneura amatoria in Manabí Province, Ecuador. The vivid red color on these is spectacular and surprisingly difficult to spot in deep shade.

Pair of Protoneura amatoria ovipositing in tandem. Protoneura typically oviposit on floating vegetation and debris, the female bending her abdomen so much that it is wedged up between her wings and nearly comes into contact with her thorax; the male usually assumes an erect "sentinel" position, often flapping his wings to maintain support. This pair was ovipositing on a loose piece of wood and the flapping male propelled their little "boat" across this small stream-side pool, although I assume that was unintentional.

The Spotted Spreadwing (Lestes congener): A Quick Look

2011-11-19T10:03:00.001-08:00

A reader recently requested that I write a post on the spreadwings (Lestes) in the region—something I had been thinking about for a while, but I haven’t been able to sit down at the blog machine much lately. So for now, I’ll just present a few words and images of one of the more common Northwest Lestes, and the one which is most expected during the tail end of the season in this region (and I think over much of its range, which is a significant portion of the United States and southern Canada).

Male Spotted Spreadwing, Lestes congener
(close-ups of the photo at top): the head and
thorax above, the end of the abdomen below.

The Spotted Spreadwing (Lestes congener) is fairly distinctive among the Northwest species: its thorax is mostly slaty gray over the dorsal areas with minimal, if any, metallic colored reflections, and largely lacking obvious pruinescence; the pale antehumeral (“shoulder”) stripe is very thin and light brown in color—never pale blue or greenish-blue; the pale pruinescence at the tip of the abdomen is limited mostly to the last two segments—S9 and S10, with just a thin, partial coating dorsally on S8.

There is often times a very thin pale median stripe on the thorax too, but not always. There are one or two dark elongated spots—what this species is named for, low on each side of the thorax, and often visible from a lateral view (see the female below). Other species, at least sometimes, have these too, so don’t assume you’re looking at this species if you see spots.

If you can see them, the males’ paraprocts (lower abdominal appendages) are short—about half the length of the longer curved cerci (upper abdominal appendages). The Archilestes (California and Great Spreadwings) have short paraprocts too, but they are noticeably bigger species with unique thoracic patterns. Our other Lestes, however, all have longer paraprocts. As always, I encourage in-hand examination if you want to make sure.

Female Spotted Spreadwings are very similar to males in overall pattern and coloration, but have little pruinescence, especially on the abdomen. Their eyes are always brown unlike the females of our other species which are sometimes, at least, blue (the females of some species are polychromatic with either blue or brown eyes at maturity). The ovipositor is relatively short, but this can be difficult to judge without experience or comparison to other species. Some other species have short ovipositors too.

Female Spotted Spreadwing, Lestes congener.

The species most similar to Spotted Spreadwing in this region is the Black Spreadwing (Lestes stultus—possibly a subspecies of Emerald Spreadwing, L. dryas, but currently considered a valid species), although it is largely restricted to lower elevation and foothill areas of Northern California and southwest Oregon. It also has an earlier flight season (with some overlap).

The Black Spreadwing has a more robust build—females especially, and quite often has more obvious colored metallic green, purple, or bronze reflections on the thorax (sometimes abdomen too). The males’ paraprocts are longer with angled tips that are vaguely foot-shaped; the female’s ovipositor is a bit longer and more hefty.

Another difference is that male Black Spreadwings often, but not always, have more extensive pruinescence at the end of the abdomen, extending more noticeably onto S8. I’ve also noticed a little difference in the shape of the pale antehumeral (“shoulder”) stripe—at least on males: on Spotted it tends to be a little constricted before a more bulbous tip at the posterior end; on Black it is more evenly tapered. This is a subtle difference and subject to variation (like all characteristics). Again, I encourage in-hand examination of the structural differences if you want to be certain.

So look for the late-flying Spotted Spreadwing if you still have some decent weather in your area—I’m thinking the warmer parts of Northern California at this date. I don’t expect to see anything in my neck of the woods until next spring, but it will be much longer until the Spotted Spreadwings are out again!

Another late visit to Ice House Lake

2011-11-10T18:25:00.001-08:00

Facing a forecast of 60°F and sunny skies on a day off from work, I couldn’t pass up the chance to get out to one of my favorite spots in the region and see what was still flying. I went out to Ice House Lake which is just off the Columbia River in Skamania County, Washington. I wrote about a previous visit here in Recent Outings on the Lower Columbia.

Many of the species I saw on that previous trip were still flying today, but in smaller numbers in some cases (as would be expected on this late date). The dominant species today where California Spreadwing (Archilestes californica) and Autumn Meadowhawk (Sympetrum vicinum; the ovipositing pair above), both still going strong. There were also a few Saffron-winged Meadowhawks (S. costiferum), several darners—the two I saw well were Shadow Darners (Aeshna umbrosa), and a few Tule Bluets (Enallagma carunculatum). Below are a few photos from today...

California Spreadwings (Archilestes californica): two males sharing a perch on the left; a female on the right.

Male Autumn Meadowhawk (Sympetrum vicinum) on the left; male Saffron-winged Meadowhawk (S. costiferum) on the right.

Odonate Magnet

I was frequently used as a perch if I stood still in the sun. Mostly it was Autumn Meadowhawks that were trying to sun themselves on me, but a few California Spreadwings landed on me as well. One spreadwing landed on my thumb and just wouldn’t leave, so I took a few close-ups of him.

A male California Spreadwing (Archilestes californica) on my thumb.

A male Autumn Meadowhawk (Sympetrum vicinum) on my leg.

Obelisking

I found one male Tule Bluet (Enallagma carunculatum) which was obelisking, but rather than for keeping cool on a hot day, it was trying to warm up on a cool day. This was the first time that I noticed an odonate obelisking for this purpose. Read more at Obelisking: Sticking it Where the Sun Shines. The pond damselflies don’t obelisk as much as some other groups of odonates, and when they do, they don’t really get the abdomen hoisted up very high. Maybe they don’t have the muscle strength needed to get that long abdomen (relative to the thorax) very far above the horizontal.

A male Tule Bluet (Enallagma carunculatum) obelisking in order to warm up—raising its abdomen up to absorb more solar radiation.

I also photographed an Autumn Meadowhawk (Sympetrum vicinum) perching on the sunny side of a wooden stake. This oriented his body nearly perpendicular to the relatively low sun. In a sense, this was kind of a “lazy obelisk” since he was just hanging on the side of an object; or maybe “smart obelisk” is more appropriate since he was expending far less energy (I presume) than if he was holding his abdomen up in the air. What do you think?

Male Autumn Meadowhawk (Sympetrum vicinum).

Another Aeshna

Lastly, here’s a photo of a Shadow Darner (Aeshna umbrosa) which let me get one shot before it bolted. Can you see all the characters that point to this species? Review Sorting Paddle-tailed and Shadow Darners Out-of-Hand if you’re not sure.

Male Shadow Darner (Aeshna umbrosa).

Halloween Fun

2011-10-31T06:33:00.000-07:00

Greetings from the Umbrosa System in the Aeshna Cluster.
Take me to your Odonatist...

Sorting Paddle-tailed and Shadow Darners Out-of-Hand, Part 2

2011-10-30T12:20:00.000-07:00

This is the continuation of Sorting Paddle-tailed and Shadow Darners Out-of-Hand, Part 1. Read that post first if you haven’t already...

4m. S10 With/Without Pale Dorsal Markings (Males Only)

Left to right: typical male Shadow Darner with black S10
male Paddle-tailed Darner with blue on S10; atypical
male Shadow Darner with blue on S10.

This character is often pretty easy to see and assess on perching individuals: the top of S10 (the posterior-most abdominal segment where the cerci and epiproct are attached) is either all black (Shadow Darner) or clearly has blue spots—often partially fused (Paddle-tailed Darner).

I have some male Shadow Darner specimens with small, very obscure pale areas on S10 which may not even be visible in the field. However, I have photos of one exceptionally colorful (more blue than normal) individual which had obvious pale markings on S10, although they were less well-defined than they are on Paddle-tailed. If it wasn’t for that individual, I might have ranked this character a little bit higher in usefulness. On the other hand I have yet to see the opposite variation (lack of, or very small and obscure spots) on male Paddle-tailed Darners, although it’s not impossible. I suppose the rule of thumb here is that if S10 clearly lacks any pale markings, Shadow Darner is a safe bet; the presence of obvious, sharply-defined pale markings very likely indicates Paddle-tailed, but consider the possibility of odd-ball individuals. Again, I remind you to not rely on any single character if possible.

Female Shadow Darner on left; female
Paddle-tailed on right. S9, S10, and
bases of broken cerci. On both, note
the small pale areas on the posterior
edge of S10 where the cerci attach.

This character actually works pretty well for females too, but because of some complicating factors I decided to make it a “male only” character. First, on female Paddle-tailed those pale S10 spots tend to be smaller and less well-defined compared with males, so a closer look is often required to evaluate them. Another complication is that small areas on the posterior edge of S10 adjacent to the cerci are usually conspicuously pale on females of both species. On Paddle-tailed Darner, these don’t stand out as separate spots from the usual bigger pale spots unless you get a very close look; on Shadow Darner you may see those pale areas on the posterior edge and not realize that they aren’t the spots (see the comparison at right). Those images show a big difference on S9 too (the uppermost segment), but that is quite variable on Shadow Darner.

4f. Shape of Dorsal Abdominal Spots (Females Only)

Female Shadow Darner on left; female
Paddle-tailed on right. Middle abdominal
(part of S3 to S7) segments.

This is one of those tentative characters which appear to be helpful at this time, but that could change with additional observations. There are two things to look at on the middle abdominal segments (primarily S4–S6): the pair of spots at the posterior end of each segment and the smaller, roughly triangular spots just anterior of middle (I’ll refer to them as “middle spots” for brevity).

On female Shadow Darners, the posterior spots are usually narrow bars with a more-or-less flat (can be slightly convex or slightly concave) anterior edge; the middle spots are vary narrow and only slightly triangular with the inner ends just a little wider than the outer. If they are more clearly triangular, the inner side is less than half the the length of the anterior side.

On female Paddle-tailed Darners, the posterior posts are more oval with a clearly rounded anterior edge (there may be small concave “divets” along that edge); the middle spots are more obviously triangular with the inner edge more than half the length of the anterior edge.

5m. Epiproct Color (Males Only)

I started noticing in my photos that the epiproct (the lower abdominal appendage) on male Shadow Darners, when viewed dorsally, is mostly very pale off-white with a black border. The epiproct on most male Paddle-tailed Darners is all dark (medium brown in the middle if you get a close look), however there seems to be some regional variation in this. You can see the differences in images in section 4m above—it’s pretty obvious when you compare the two Shadow Darners (left and right) with the Paddle-tailed (middle). The epiproct is the shorter appendage between the cerci.

This difference appears to hold up pretty well over most of the Northwest, however I have some specimens of Paddle-tailed Darner from the very arid Alvord Basin in southeast Oregon (part of the Great Basin) which have pale epiprocts very similar to Shadow Darners. I’m going to keep an eye on this character, but it seems to be useful in the more humid, cooler parts of the region, at least.

5f. Presence/Absence of Cerci (Females Only—NOT Reliable)


End of abdomen of Shadow Darner on the left; Paddle-tailed on the right.

This is not a reliable identification character, but it’s interesting enough to merit mention. It is not unusual to come across mature female darners that are missing their cerci. Presumably they break off during daily activities like ovipositing, or maybe during copulation. Female Shadow Darners are a little different in that they lose their cerci at such a high rate that it seems to be routine for them. I don’t have a single photo or specimen of a female Shadow Darner with her cerci intact, but I do have many examples of other species in possession of them. I’d say that any obviously mature female Aeshna with intact cerci during the latter end of the season (well after most have emerged) is very likely not a Shadow Darner, but definitely don’t rely on this alone.

I can’t help wondering if female Shadows remove their cerci intentionally as some kind of signal—that they are mature enough to copulate, or that they have already copulated. I don’t know, but I can’t imagine why else they would lose their cerci so much more often than other female darners. A couple of times I caught a female Shadow Darner and, as soon as I pulled her out of the net, the end of her abdomen curled toward the mandibles and “snip, snip”—both cerci fall away. In those cases it was certainly self-inflicted, and the fact that both cerci were bitten off—not just one of them, suggests to me that it wasn’t an “accidental”, random event. We may never know for sure, however.

6m. Shape of Anterior Thoracic Stripes (Males Only)


Left to right: male Shadow Darner with continually widening anterior thoracic stripes; male Paddle-tailed Darner with constricted stripes; male Paddle-tailed Darner with broken stripes.

Most male Shadow Darners have relatively heavy anterior thoracic stripes which continually widen from front to back (wedge-shaped). On most male Paddle-tailed Darners those stripes are usually either constricted or completely broken just before the terminal expansion.

There is some overlap in this character: occasional male Paddle-tailed Darners have anterior thoracic stripes which appear parallel-sided before the terminal expansion, and some male Shadow Darners have a very slight constriction before the terminal expansion. For now it appears that this character is useful if it is either wedge-shaped or obviously constricted (or broken), and anything in-between is not useful. As always, don’t rely on any single character whenever possible.

7m. S2 Mid-Dorsal Stripe (Males Only)

The dorsal surface of S2. Two male Shadow Darners on the left; three Paddle-tailed on the right.

This one certainly needs further assessment, but it appears that the mid-dorsal stripe on male Shadow Darners is typically complete and expands (either at a spot or into a funnel-shaped terminus) anterior of the perpendicular stripes on either side; on male Paddle-tailed Darners the mid-dorsal stripe on S2 is complete or broken and often without any obvious expansion; if it does expand at a spot, the expansion is at the level of the perpendicular lateral stripes.

Something I just noticed while looking at these is that Paddle-tailed Darner has a wide black posterior margin on S2, while Shadow Darner has an extra thin blue line within the black margin. That extra blue line is not always well-defined, but it is present on all of the male Shadow Darners that I have photographed. I also see some differences in the adjacent areas of S3—the extent of blue on the sides and whether they connect across the anterior end of the segment, although that is obviously variable. I’ll look into those some more too.

Conclusion

I’ve always thought of Shadow Darner as darker overall than Paddle-tailed Darner since the lateral thoracic stripes and dorsal abdominal spots average smaller (and maybe the name has a psychological effect too). I have come to realize, however, that Shadow Darner makes up for the limited color in some places with added color in other places—the anterior thoracic stripes and the top of S2 on males, for example. And, of course, they have those ventral pale spots on the abdomen too. You just have to know where to look. Out-of-hand identification really boils down to understanding where Paddle-tailed Darner has more color, and where Shadow Darner has more color.

Over time, I’m sure, some of these characters may prove to be too variable to be very useful, while other potential field marks will come to light. It’s always interesting to see how geographic variation plays a role too—as it appears to do so with male Paddle-tailed Darner epiproct color.

As always, I appreciate feedback, especially if your observations differ from mine.

Sorting Paddle-tailed and Shadow Darners Out-of-Hand, Part 1

2011-10-28T17:40:00.000-07:00

Paddle-tailed Darner (Aeshna palmata) and Shadow Darner (A. umbrosa) are both rather common and widespread—nearly ubiquitous, I’d say—across the Northwest during the latter part of summer and fall. Not only are they superficially quite similar in appearance, but they are also frequently found flying together. Add to this situation the fact that more and more people are relying on photographs and binoculars instead of nets to identify odonates, and it becomes evident that “new” field marks are needed to sort out these bugs. In this post I’ll summarize the various differences between these two species and explain which in particular seem to be the most useful, at least at this time, for “out-of-hand” identification. Some of these have been well-understood for a long time and some have only recently come to light.

The "Classic" Field Marks

When I started identifying odonates in the mid-90s, separating these two species involved the relative thickness of the thoracic stripes, the relative size of the dorsal blue spots on the abdomen, whether or not there were blue spots on the dorsum of S10 (the posterior-most abdominal segment), whether or not there were pale spots on the underside of the abdomen, and whether or not there was a dark face line. The latter three characters work well much of the time, but the others are not only variable, but also quite subjective and difficult to assess without experience and comparative material. You also hear about Shadow Darners frequently having an extension or “flag” at the top of the anterior lateral thoracic stripe. It is more often well-developed on Shadow Darners, but I find it variable enough on both species to be unreliable.

Ruling Out Other Species First

Before you can figure out whether your subject is a Paddle-tailed or Shadow Darner, you have to first know that it is one of those species. These two species (including males and females) have a pair of pale, narrow to moderately wide, relatively straight stripes on the side of the thorax. These are often mostly yellow, but transition to pale blue or greenish-blue at the tops (occasionally more pale blue or greenish-blue overall), and they are pale enough and contrast with the otherwise dark brown thorax enough to be conspicuous from a distance.

Male Paddle-tailed Darner abdominal
appendages, lateral view. You see two
spines because one of those is on the
opposite cercus.

Males have cerci (upper abdominal appendages) which are somewhat flattened, but twisted so they appear relatively wide from the side. Each cercus also has a spine near the tip below the rounded apex which is small, but easily seen through binoculars if you’re close enough, and in good quality photographs (it’s just barely visible in the photo above). I prefer to label this type of Aeshna cercus as “spined”, but you will also see some authors describe it as “wedge” or “paddle” in shape. Males of two other species in this region have similar appendages—Walker’s Darner (Aeshna walkeri) and Lance-tipped Darner (A. constricta), but these are more restricted in range and habitat, and are not frequently encountered in the Northwest. I may discuss those species in a later post.

Females of some other species are very similar to Paddle-tailed Darner and they can be problematic to differentiate. In particular, female Variable Darner (Aeshna interrupta) can be extremely similar when they have relatively bold thoracic stripes. In that case, small structural differences are the only way to confidently identify them and those are difficult to see out-of-hand. Sometimes you just have to accept that not everything is identifiable.

Caveats

I started to go into a long discussion of a couple of issues, then I thought it best to restrict it to some brief statements for this post. 1) Remember variation. Practically every character varies to some degree or another—sometimes a little, sometimes a lot—and the extent of variation of some characters is not yet fully understood. 2) Because of variation, don’t rely on any single field mark whenever possible. These issues really deserve a much more thorough discussion, but let’s keep it there for now and move on...

What to Look For

Differentiating Paddle-tailed and Shadow Darners depends, in part, on whether your subject is a male or female, although some characters work for both. Below is a simple table to guide you. The characteristics are roughly in order of usefulness as far as I have determined, with the most useful at the top. The first three work for both males and females. This ranking is pretty subjective, and is subject to change if better information comes along. In other words, I could easily change mind mind if additional observations warrant it. Some of these criteria I consider tentative and particularly in need of further assessment (indicated with *), but at this point they appear to be helpful (remember the caveats about variation and relying on a single character).

	Males	Females
1	presence/absence of ventral abdominal spots
2	lateral pale mark on S1
3	face line (if either bold and black, or absent—not if thin)
4	S10 with/without dorsal pale markings	shape of dorsal abdominal spots*
5	epiproct color* (regional?)	presence/absence of cerci—not reliable, but worth noting
6	shape of anterior thoracic stripes*
7	shape of pale markings on dorsum of S2*

1. Presence/Absence of Ventral Abdominal Spots (Males and Females)

Male Shadow Darner abdomen, middle segments, ventral surface.

Abdomen of female Shadow Darner on
left; Paddle-tailed on right. Ventro-lateral
view. Red arrows point to the pale spots.

Shadow Darner has paired pale spots on the underside of the abdomen, most prominently on S4–S6 (blue on males—as in image above, blue or tan on females) and Paddle-tailed lacks them being more-or-less uniform in tone/color. Those spots are not so obvious on some female Shadow Darners, but you should see them with a pretty good view. The image at right includes a ventro-lateral view of the abdomen of a pretty dull female Shadow Darner on the left and a female Paddle-tailed on the right. The pale spots don’t stand out so well on this female Shadow Darner and require a close look.

This is by far the best field mark when you can see it—the trouble is that it is often hard to see in the field. Look back at my post Fun With Darners! which has photos of three perched darners. All of the darners I saw that day were perching with their bellies toward the vegetation and it was tricky, at best, to get a view of the underside of the abdomen without scaring them off. If you can get a side view of your subject you may just be able to see the spots if they are there.

Note that a few other Northwest species also have pale ventral abdominal spots, but they are not otherwise especially similar to Shadow Darner and they are more restricted in range and habitat preference.

2. Lateral S1 Pale Mark (Males and Females)

Left to right: the thorax and first two abdominal segments of a male Shadow Darner—the first abdominal segment (S1) is spot-lighted; Shadow Darner S1, lateral view; Paddle-tailed Darner S1, lateral view.

Female Paddle-tailed Darner. The white
arrow identifies the S1 lateral pale mark
adjacent to the black posterior margin.

Paddle-tailed Darners have a vertical, irregularly-shaped (usually thicker toward the bottom) pale mark on the side of S1, adjacent to the posterior black border; on Shadow Darner there is no pale mark adjacent to the black border, but there is an extremely thin pale streak within the black border (sometimes there are only minute traces of that pale streak, and I assume it can be totally lacking on some individuals). In each species I see virtually no variation of this character that approaches the appearance of the other species, and it works for both males and females.

You don’t even need a perfectly lateral view to see that pale S1 mark on Paddle-tailed Darners; even with an oblique view—with the wings obscuring the base of the abdomen, that mark is often visible like in the photo at right. Incidentally, of all of the “spined” darners that occur in the Northwest, the Paddle-tailed is unique in having that irregular pale mark adjacent to the black border. On the other hand, other species which have females that are similar to Paddle-tailed Darner—especially Variable Darner, have that mark too, so just be aware.

3. Face Line—If Either Bold and Black, or Absent (Males and Females)

Left to right: male Paddle-tailed Darner with a bold black face line; female Shadow Darner lacking a black face line; male Shadow Darner with a very thin (not useful) face line.

This character is variable on both species, but it’s a good field mark if that line is rather bold (indicating Paddle-tailed Darner) or if it is absent (indicating Shadow Darner; obviously it takes a pretty good look to see that it is absent). If it is there but very thin it isn’t of any help. I find that male Shadow Darners frequently have a thin dark face line—more so than females. It is important to realize that there is a suture across the face where that line is (when present) and because of the angle of lighting, it can appear dark even when there is no dark pigment. Even in that case it typically appears rather thin and usually brown/gray rather than black, and falls in the category of “not useful”.

This topic is continued at Sorting Paddle-tailed and Shadow Darners Out-of-Hand, Part 2.

Recent Outings on the Lower Columbia

2011-10-23T14:43:00.000-07:00

I was able to get out on a couple of warm, sunny days this week. I may not have that opportunity again around here for several months, so I enjoyed it while I could! Several species are still relatively abundant at this time of year in this area, while others are definitely winding down. Many summer species are gone for the year, of course.

Last Sunday (16 Oct) I went to Ice House Lake in Skamania County, Washington. It’s right across SR-14 from the bridge that spans the Columbia River to Cascade Locks, Oregon. There are often several anglers around the margin, but on that afternoon I had the place, and the odonates, all to myself. It was fun.

A couple of reasons why this place is special is that it’s one of the few places in Washington where the Pacific Clubtail (Gomphus kurilis) occurs, and it has a population of Chalk-fronted Corporal (Ladona julia) which is unusual for a low elevation site (about 175 feet above sea level) in this region. Neither of these species is flying at this time of year, but there is plenty more to keep me occupied. Below are several shots from Ice House Lake.

Saffron-winged Meadowhawk (Sympetrum costiferum) was one of the common species. Here’s a male:

The aptly named Autumn Meadowhawk (Sympetrum vicinum) was also present in good numbers. Here’s a male followed by a female:

The California Spreadwing (Archilestes californica) was the dominant damselfly. Here’s a female:

Present, but definitely winding down in numbers were Tule Bluets (Enallagma carunculatum). This is a male:

On Tuesday (18 Oct) I visited Trojan Park in Columbia County, Oregon. The ponds here are much larger than the little Ice House Lake, but had a bit less diversity. It’s always interesting to see how different locations differ in species diversity and abundance at the same time of year.

I saw no Saffron-winged Meadowhawks at Trojan Park, but Striped Meadowhawk (Sympetrum pallipes) was abundant (vs. only one or two at Ice House Lake). Autumn Meadowhawk seemed to be similar in abundance at the two locations. Trojan Park also lacked California Spreadwings, with only the little Tule Bluet representing the damselflies.

Here’s another male Autumn Meadowhawk:

A female Striped Meadowhawk:

A very cooperative female Olive Clubtail (Stylurus olivaceus) which wandered over from the Columbia River, no doubt:

Also at both locations were a number of Paddle-tailed and Shadow Darners (Aeshna palmata and umbrosa, respectively). I got a number of shots of both species, but I’ll save those for an upcoming post on differentiating them.

Fun With Darners!

2011-10-15T20:12:00.000-07:00

The sun made an effort to shine this afternoon (with variable success), and temperatures hovered around the very low 60s. I figured I should take the opportunity to get out and see what I could find flying, so I wandered the grounds and trails of the Columbia Springs Environmental Education Center in Vancouver, Washington.

There wasn’t much variety. Other than a single meadowhawk (Sympetrum) that I spooked from a walkway, all I saw were darners (Aeshna). Two species of Aeshna, Paddle-tailed Darner (A. palmata) and Shadow Darner (A. umbrosa), are particularly common and widespread across the Pacific Northwest during the latter part of the season—mostly from around July on; into November if there are lingering warmish, sunny days. These two species are also very similar in appearance, at least superficially, and are often found flying together.

Today I saw a few darners patrolling the wetlands or hawking insects high overhead, but most of the action was at patches of Himalayan blackberry where many darners were perching and soaking up as much solar energy as they could. The best spots were along trail cuts in the blackberries where the darners would perch on the bramble “wall” that was facing the sun.

Perching darners don’t often let you get very close and they very frequently fly off before you even spot them. I tried really hard, moving slowly and stopping periodically to scan the sun-soaked vegetation before continuing. I did spot some perching males and I was able to photograph a few of those before they took off, but many more got away. I don’t know how many times I stopped to look over the vegetation, not see anything, then spook up one or more darners that were right in front of me as I started moving again. The colorful males are hard enough to spot while they’re perching, but the relatively dull females are even more challenging. I was able to photograph one female which reperched shortly after I spooked it.

Once you spot a perched darner, you have to approach very slowly and make no sudden moves. Some individuals are more approachable—maybe because they haven’t warmed up enough, and I was even able to catch one by hand for a few in-hand photos (I didn’t take a net out with me today).

I plan to offer a thorough comparison of these two darners in a future post, so for now I just offer you a few photos from today. I’m going to leave them unidentified for the time being, but both Paddle-tailed and Shadow Darners are represented. See what you can do with them and feel free to comment on what you think each one is.

A male...

Another male...

A female...

A hand-held male...

Just a Photo: A Table for One

2011-10-14T10:58:00.000-07:00

This was along Mill Creek outside of Walla Walla, Washington a couple weeks ago. There were a lot of meadowhawks (Sympetrum) around—mostly Band-winged Meadowhawk (S. semicinctum) and Striped Meadowhawk (S. pallipes), soaking up a little afternoon sun when the clouds parted. We found this good-sized, plump mantid just off the trail with some Band-winged Meadowhawk remains nearby. I have to assume that the mantid caught and devoured the meadowhawk (its head and thorax, anyway, leaving the wings and abdomen as scraps), and perhaps it was waiting to ambush more that landed within reach of its raptorial forelegs.

The mantid isn’t the native Litaneutria minor, which is a small species (no more than about 1.5 inches in length—this one was about 4 inches) and finely patterned with speckles. I presume it is one of the non-natives, but I couldn’t tell you which one. I wonder if it’s a gravid female with that very plump abdomen—or else she is just full of Sympetrum.

The mantid standing up next to that leaft makes it look like she’s at a dinner table waiting for the next course. She also looks like she is going to pick her teeth with that piece of straw in her forelegs. Wait... ...now that I look at it very closely, I can see that it’s actually an insect tarsus—probably from a mantid. I don’t see her right rear leg, so maybe it’s hers? Maybe it came off in the struggle with the meadowhawk or she tangled with another mantid. I don’t know.

Here’s another view, so technically this isn’t just “a” photo...

Postscript

This appears to be a European Mantis, Mantis religiosa. Thanks to those who commented.

Just a Photo: Chaotic Cluster

2011-09-30T08:00:00.000-07:00

This photo offers a contrast to an earlier post, Just A Photo: A Table for Eight Please? I was visiting Twentymile Creek in southeastern Oregon last year and there were loads of these Sooty Dancers (Argia lugens) ovipositing in tandem on floating leaf debris. It appears that each female is inserting eggs into the underside of the leaves by curving the abdomen up. Unlike the more civilized four pairs of Vivid Dancers (A. vivida) in that earlier post, these four couples are all over the place and all over each other. It takes a little effort to figure out which male is in tandem with which female!

Just as in that earlier post, this is a case of contact guarding—each male remains attached to the female while she oviposits in order to prevent other males from copulating with her and removing or displacing his sperm. This ensures that the eggs she is depositing at the moment were fertilized by him.

ID Challenge #3 Answer

2011-09-27T11:29:00.000-07:00

Click image for a larger version.

All you have to work with in ID Challenge #3 is a pair of wings, but they are patterned very distinctively. A scan through any of a number of field guides to North American dragonflies (of continental or regional scope) would narrow down your choices to two, or maybe three species. That’s the easy part. The challenge is figuring out which one of those is the owner of our pair of wings.

So let’s start at the top: is it a dragonfly or a damselfly? The hind wing is noticeably more broad than the fore wing—particularly at the base, so it’s a dragonfly. You also won’t find any damselfly with a wing pattern like that anywhere in North America (or anywhere in the world as far as I’m aware, but I could be wrong about that).

Now let’s figure out the family. In ID Challenge #1 Answer I talked about using the anal loop in the hind wing to figure out that mystery dragonfly’s family. In this case too, it is more-or-less foot shaped with something that you could call a “heel” and something that you could call a “toe” (see the close-up at right). This puts it in the skimmer family—Libellulidae. [...in the limited sense. This is one of those places where you can get caught in the crossfire of dueling authorities—it depends on who you read. According to some, Libellulidae includes the subfamilies Macromiinae, Corduliinae, and Libellulinae, in which case the foot-shaped anal loop would indicate the subfamily Libellulinae; according to others Libellulidae has no subfamilies, with Macromiidae and Corduliidae being families on their own, and this is the taxonomy that I go with until I see something resembling consensus.]

One of the possible contenders that you might have picked out in a North American field guide is the Prince Baskettail (Epitheca princeps) which has a superficially similar wing pattern, although it can be ruled out on the basis of my statement that our subject occurs in the Pacific Northwest. The Prince Baskettail doesn’t occur west of the Rockies, but let’s consider it anyway just to make sure. It’s in the family Corduliidae [or subfamily Corduliinae] and like other members of that family, its anal loop is more club-shaped with an irregular expansion that isn’t clearly foot-shaped. Something else that rules out the Prince Baskettail is the shape of the dark spot at the base of the hind wing: bar-shaped on our subject; distinctly triangular on the baskettail.

That leaves two choices in the skimmer family, Libellulidae [or subfamily Libellulinae], with wings like ours: Twelve-spotted Skimmer (Libellula pulchella) and female Common Whitetail (Plathemis lydia)—the male of the latter species has a very different wing pattern. [Another taxonomic sidenote is that the Whitetails are sometimes placed in the genus Libellula, but these days most authors place them in Plathemis.] These are both widespread species across most of the continental US and southernmost Canada. You can view distribution maps for Libellula pulchella and Plathemis lydia at OdonataCentral.org.

There are some pretty consistent differences between the Twelve-spotted Skimmer and the female Common Whitetail in the shape and extent of the dark spots on the wings, but it’s helpful to know a couple of venational landmarks to see exactly how they differ. Take a look at the wings on the right (here I’m using the wings of the Western Pondhawk, Erythemis collocata, since they are completely clear and all of the veins are visible): the shaded red spaces are the “triangles”, and the blue dots mark a major junction known as the “middle fork” in each wing. Notice how the middle fork is at the inner corner of a roughly triangular space which is highlighted in green. These are venational features that all dragonflies have in both the fore and hind wings and are easily recognizable once you’re familiar with them. The foot-shaped anal loop in the hind wing should stick out like a sore thumb by now, so you know which family contains Erythemis...

So, take another look at our subject. Let’s start with the dark bar at the base of the fore wing—it extends across the base of the fore wing triangle, but not any further, and the bar does not extend into the triangle itself. The basal bar in the hind wing similarly doesn’t extend much past the triangle (which is hidden within the dark bar). Both basal bars have neat, clean edges along their posterior or trailing edges (the side that is “down” on your screen). Next we’ll move on to the middle spot in each wing which have a very jagged inner edge where they extend inward to the middle fork and filling the triangular space which is highlighted in green above. These features point us clearly to the female Common Whitetail, Plathemis lydia.

On a Twelve-spotted Skimmer (Libellula pulchella), the basal bars extend noticeably beyond the triangles and “ooze” toward the trailing edge along a pretty sloppy edge—especially into the fore wing triangle, and the middle spot does not extend inward as far toward the middle fork, leaving much of that adjacent triangular space clear. So, Twelve-spotted Skimmer has more extensive basal bars and more limited middle spots, the opposite of what you see on female Common Whitetails. Another more subtle difference is that Twelve-spotted Skimmer wings are a tiny bit narrower relative to their length, and Common Whitetail wings are a little wider relative to their length which makes them look stockier.

Here are full-width images of a female Twelve-spotted Skimmer followed by our subject again which we now know to be a female Common Whitetail for comparison. Pick out the triangles and middle forks in each example even if they are obscured by dark spots.

Twelve-spotted Skimmer (Libellula pulchella)

Common Whitetail (Plathemis lydia), female

Of course, you have to watch out for variation which can be especially significant when you’re dealing with the extent of pigments. If you search hard enough I’m sure you can find one or two individuals of either species that don’t fit the mold, and that’s why it’s important to use multiple characteristics when identifying similar species. The differences that I discussed above should make for pretty good rules of thumb, however. More than likely you’ll have the rest of the bug to examine anyway, but I thought this would be a fun and interesting exercise.

Most of those who commented on ID Challenge #3 got it right, so congratulations to them! Something like the wings of female Common Whitetail may be something that you “know”, but you may not be exactly sure how you know what you know. Whether you knew what they were or not, I hope that this explanation was helpful. Until next time...

ID Challenge #3

2011-09-22T11:30:00.000-07:00

It’s time once again for an identification challenge! All you have to go on is this pair of wings (fore wing on top; hind wing below), but it is a species which occurs in the Pacific Northwest. Most people should be able to narrow it down to a couple of options pretty easily, but which one is it?

Leave a comment to let me know what you think it is even if you’re not sure. Comment moderation will be turned on until I post the answer, so they will not be visible in the mean time.

Postscript, 27 September 2011

This challenge is now closed. The answer with a complete discussion is here.

Some Non-Odonate Critters

2011-09-19T16:03:00.000-07:00

When you spend a lot of time searching for odonates, you naturally come across lots of other fascinating animals. I thought I’d share some of the more interesting non-odonate critters that I have photographed over the years. So no dragonflies or damselflies this time around, but I hope you enjoy it.

Doros aequalis, a wasp-mimicking syrphid fly in the central Oregon Cascades. According to commenters at BugGuide.net, this species is relatively widespread across northern North America, but is rather infrequently encountered. The photo I submitted to BugGuide in 2009 is still the only one for this species, so it must be pretty scarce!

Another bee-mimicker, but this time a scarab beetle: Lichnanthe rathvoni. One day I was looking for Olive Clubtails (Stylurus olivaceus) on the Columbia River in Vancouver, Washington, and a bunch of these scattered from the upper part of the beach as I made my way through young willows and cottonwoods. I must have found them at their peak that day because I haven't seen them in such numbers since. Got to love those crazy antennae! Thanks to Chris Marshall for identifying these.

Near a hot spring in southern Malheur County, Oregon, I came across a congregation of young Burrowing Owls (Athene cunicularia) at their den. A few more youngsters and their parents were scattered around the vicinity, but these three posed very nicely at the burrow.

During a late night drive to the Alvord Basin in southeast Oregon, I found several of these katydids, Capnobotes occidentalis, which come in green and gray forms. These are both females with their long, sword-like ovipositors. The gray one was apparently trying to oviposit in the asphalt, but I can't imagine that she got very far. Thanks to Ron Lyons for identifying these.

The drive that produced the katydids above also produced a large number of Great Basin Spadefoots (Scaphiopus intermontanus) on the road. Pretty adorable as toads go, I think.

Hmm, I seem to focus on bee/wasp mimics and here's another one: the robber fly Laphria astur. I found this one on a log while hiking to a lake (to see odonates, of course) in the southern Oregon Cascades. Thanks to Rob Cannings for identifying this one.

A Western Rattlesnake (Crotalus viridis) in Oregon's Alvord Basin. I never have the right lens on my camera for photographing these when I find them, but this one turned out pretty well even if the rattle isn't visible. I think the blue tongue is a nice touch.

I have a particular fondness for tiger beetles, and this emerald green Cow Path Tiger Beetle (Cicindela purpurea) was on a different kind of path (walking/biking) at a great odonate spot—Lake of the Woods in the southern Oregon Cascades.

Yeah, definitely a thing for Hymenoptera mimics. Here are two views of a jumping spider (maybe Phidippus apacheanus) which is an apparent velvet ant mimic. The iridescent blue chelicerae are mesmerizing. This was at a hot spring in Oregon's Alvord Basin—my favorite area to look for odonates.

Obelisking: Sticking it Where the Sun Shines

2011-09-15T20:12:00.000-07:00

Odonates are ectothermic creatures which means that their body temperature is, for the most part, not self-regulated, but is instead regulated by their environment. This is commonly known as being “cold-blooded”, which isn’t really accurate—at least not when their environment is warm. When it is cold out, odonates are cold and aren’t doing much of anything; when it is warm (and sunny) they are quite happy; when it is oppressively hot, well, something has to be done about that—even for these sun-loving insects.

One strategy odonates employ to avoid excessive heat is to simply get out of the sun. On extremely hot days, you may find congregations of odonates of multiple species enjoying the shady side of a tree. Typically it has to be really hot for odonates to resort to that behavior, however. In general, odonates (males in particular) don’t want to miss out on reproductive opportunities at their favorite haunts, and time spent avoiding the sun is time spent not reproducing.

Obelisk of Senusret I in
Heliopolis [Public domain],
via Wikimedia Commons

Another strategy to avoid overheating which is more commonly observed among some odonates is obelisking. This means holding their abdomen up toward the sun so that the long axis is parallel to the solar rays. I’m not sure how long this term has been in use for this behavior, but obviously it was reminiscent of Egyptian obelisks to someone. The advantage of this method is that they don’t have to leave their pond or stream to keep their cool.

How does obelisking help odonates prevent overheating? By aiming their abdomen toward the sun, they reduce the amount of body surface area that receives direct sunlight. Consider the obelisk at right. When the sun is directly overhead, the surfaces that are receiving the highest density of sun rays are the facets at the top (a relatively small percentage of the total surface area); the sides are nearly parallel to the sun rays so they are receiving a much lower density of solar energy per unit of surface. When the sun is low in the sky, it is the long, vertical surface (a relatively large percentage of the total surface area) that is nearly perpendicular to the solar rays, and it receives the greatest density of solar energy.

Male White-faced Meadowhawk (Sympetrum obtrusum), Jackson County, Oregon.

Female Band-winged Dragonlet (Erythrodiplax umbrata), Los Ríos Province, Ecuador.

Another way to think about it is in terms of the size of the shadow cast by the obelisk. When the sun is high in the sky, the obelisk’s shadow is pretty small. This means that the obelisk is absorbing a relatively small slice of the solar energy that would otherwise hit the ground if the obelisk wasn’t there. When the sun is low in the sky, the obelisk’s shadow is very long and, at this time, the obelisk is absorbing a larger percentage of the sun’s energy. The more solar energy something absorbs, the more heat that is produced.

So, for a odonate on a hot, sunny day, obelisking is all about making its profile (from the sun’s point of view), and therefore its shadow, as small as it can in order to minimize the amount of solar radiation that is absorbed by its body. This allows them to regulate their temperature without having to abandon the action at their local pond or stream (as long as it isn’t so hot that they have to seek shade instead).

Male Gray Sanddragon (Progomphus borealis), Graham County, Arizona.

Male White-belted Ringtail (Erpetogomphus compositus), Wheeler County, Oregon.

Not all odonates employ this technique for staying cool. Among dragonflies you see it most regularly in the clubtails (Gomphidae) and skimmers (Libellulidae), and within those families particular species are frequent practitioners while others don’t seem to do it at all. The Blue Dasher (Pachydiplax longipennis)—like the one in this blog’s title banner, is one of those frequent practitioners. The tropical Micrathyria also frequently obelisk, and three species are shown here.

Male Spot-tailed Dasher (Micrathyria aequalis), El Oro Province, Ecuador.

Male Micrathyria ocellata, El Oro Province, Ecuador.

Male Micrathyria pseudeximia, Manabí Province, Ecuador.

I’ve read that the impressive Dragonhunter (Hagenius brevistylus)—a huge clubtail of eastern North America, has its own variation which is to point its abdomen down, away from the sun, which has essentially the same effect. This is a big, beefy species and I imagine that it takes a lot of energy to hold that abdomen up for any length of time! Perhaps other odonates which typically perch by “hanging” (with the abdomen down) obelisk in this manner too, but it isn’t nearly as obvious as the sunward style.

Some damselflies obelisk as well, although apparently not as often as some of the dragonflies, at least in my experience. In particular the broad-winged damsels (Calopterygidae) and some other groups like the dancers (Argia) are known to use this method of thermoregulation on occasion.

Female Beaverpond Clubtail (Gomphus borealis), Somerset County, Maine.

Female Paiute Dancer (Argia alberta), Harney County, Oregon.

But wait, there’s more! Something I realized only recently while reading Philip Corbet’s monumental Dragonflies: Behavior and Ecology of Odonata (1999)—it’s really impossible to open up this book and not learn something new—is that obelisking isn’t strictly about keeping cool. When the sun is low and the air temperature is relatively cool, an odonate may obelisk in order to warm up. This time the abdomen is not pointed toward the sun, but is instead held up with the long axis perpendicular to the solar rays in order to maximize its exposure. I’m not certain that I have observed obelisking in this context, but I’ll be watching for it.

Don’t Fear the Dragonfly

2011-08-24T16:46:00.000-07:00

I wrote this post several month ago right after starting this blog, then I decided to let it “marinate”. I wondered if maybe I was making too big a deal out of the topic, so instead I wrote and published Do Dragonflies Bite or Sting? as a more informative piece without the psychoanalysis (something for which I have absolutely no training). Since then I have noticed an interesting trend. That post has received far more views than any other post on my blog, and nearly all readers found it with Internet searches using phrases like, “dragonfly bite”, “dragonfly sting”, “do dragonflies bite”, and “do dragonflies sting”, and many other variations along those lines. In fact, those search phrases are the top four phrases which have brought visitors to my blog. So maybe there are a lot more people being bitten or stung by dragonflies than I realize—something which I have a hard time believing, or there really is a lot of fear of being bitten or stung based only on misconceptions. I suspect it’s the latter in a majority of cases. Read on and let me know what you think.

By Dodd, Mead and Company (New
International Encyclopedia) [Public domain],
via Wikimedia Commons

A segment of the population seems to have a deep-rooted fear of dragonflies beyond the regular everyday aversion to “bugs” common to so many. I sense this fear is not the result of direct experience with dragonflies, and I also suspect many of these people don’t even understand why they feel the way they do. I just read that the phobia of dragonflies is called “dragoferosus”—a little party trivia for you. But I’m not talking about something that rises to the level of a phobia—at least I don’t think I am—it’s more of a subconscious fear.

Maybe it has to do with reputation-tarnishing folklore surrounding dragonflies. Names like “devil’s darning needle”, “horse stinger”, “ear cutter”, and “eye poker”, and the notion that during the night they will sew shut the mouths of lying children, scolding women, and cursing men sure don’t help their cause. European folklore frequently associated dragonflies with the nasty red guy downstairs with horns and cloven hooves which doesn’t make anyone popular. I don’t know—I never heard any of this bad press when I was a kid (the 70s primarily), but then maybe that’s why I never had a fear of dragonflies.

Some people certainly do think, or are afraid that, dragonflies will bite or sting them. A few months ago, soon after I started this blog I posted Do Dragonflies Bite or Sting?, and that is by far my most popular post garnering frequent Internet search hits. The short, quick response to this notion is that it doesn’t happen. A free-flying dragonfly will never bite or sting a person as a defensive measure the way a yellow jacket or honey bee might when agitated. Swat at them all you want and there will be no retaliation. The complete answer is a bit more complicated and I go into that in the above post. In the mean time, just remember the short, quick answer and you’ll be fine. So, it doesn’t seem that biting and stinging contribute in a significant way to this general fear of dragonflies.

By Drury, Dru, 1725-1803.
Westwood, J. O. 1805-1893. [Public domain],
via Wikimedia Commons

Maybe it’s the large size of some dragonflies; maybe it’s their command of the air space with powerful yet agile flight; maybe it’s that, at times, they seem to possess a level of sentience, perception, and understanding unmatched by other insects. I admit that I’m biased, but I just don’t get the sense of a conscious, thinking being when I see a butterfly flutter by. On the other hand, when I see a darner busily hunting or searching out females and it hovers for a moment to make a quick assessment of me, there’s a very real sense that there is conscious thinking going on—something far more than instinctual response to stimuli. I’m not saying that there really is this level of conscious thought going on, but the perception that it is occurring is real enough.

I’m reminded of a line from the movie The Mothman Prophecies (2002): Richard Gere’s character asks an old professor-type why the mysterious mothmen were doing what they were doing, and the response was “You noticed them. And they noticed you noticing.” Maybe when it appears that dragonflies notice you noticing, it naturally imparts a sense that they are thinking about you, and maybe that’s a little bit scary to some people?

Whatever reason people fear dragonflies, I have to think that it is based almost entirely on misinformation, misconception, and, maybe in some cases, nothing at all. Cases of biting and stinging only occur in particular circumstances (such as handling them), and even then only rarely. I have been been nibbled by dragonflies while handling them, but that was my fault, and it was always more startling than painful. I have never been stung during the many years that I’ve been chasing them. The benefits of having dragonflies around (by eating other flying insects) far outweigh any remotely possible painful interaction by multiple orders of magnitude. Any other reason to fear dragonflies simply doesn’t have substance.

Trust me. Don’t fear the dragonfly.

It's Time to Watch for Migrant Meadowhawks

2011-08-17T17:31:00.000-07:00

The Phenomenon

Around August and September there’s an intermittent phenomenon at coastal areas of the Pacific Northwest that involves the directional movement of dragonflies (typically southward) and there’s a lot to learn about what exactly is going on. This has been observed most frequently at southern Washington and northern Oregon coastal areas, with sporadic reports from further south into California. This phenomenon is commonly referred to as a migration, but whether it is truly a directed migration (like in the sense that many birds migrate south each year) or something else is one of those things that isn’t yet clear.

A nearly mature male Variegated Meadowhawk (Sympetrum
corruptum). Note the overall reddish-brown color, the pair of
yellow spots on the lower side of the thorax, and the orange
veins along the leading edge of the wings.

These movements of dragonflies primarily involve the 1.5-inch long Variegated Meadowhawk (Sympetrum corruptum), although a few individuals of other species are sometimes reported flying with them. A possible explanation for these directional movements is that Variegated Meadowhawks from northern areas fly to southern US regions in the fall to lay their eggs; their offspring emerge the following spring, and fly back north to complete the cycle. During the southward movement, there seems to be some correlation between flights at coastal areas and east winds: the east winds may push them toward the coast where they then have to take a left turn to avoid the open ocean—the result is a stream of dragonflies heading down the beach. Northward directional movements have not been reported, but spring weather conditions may not have the same concentrating effect, resulting in a more diffuse, cryptic migration.

Some years there are lots of reports of moving meadowhawks on the beaches, and some years there are hardly any. Last year—2010, was a big year for them. So much so, that people who otherwise give no thought to dragonflies at all took notice of the huge numbers, even using terms like “apocalyptic” and “plague”. The events even made headlines at local news outlets such as the Cannon Beach Gazette in Oregon. You can still see their article here.

I think it’s likely that these coastal concentrations are the result of regional topography: East winds are funneled down the Columbia River to its mouth and lots of meadowhawks go with it; when they reach the ocean they resume their southerly course. There have been some reports of meadowhawks flying onto beaches from the ocean (from the west). This suggests that some of them get blown out to the open Pacific, then have to make it back to land (or else become fish food following exhaustion). Looking at this at the bigger scale, our coastal flights may only be a small observable slice of a much more widespread migration that is otherwise invisible because the meadowhawks are so spread out.

Record Your Observations

Immature female Variegated Meadowhawk (Sympetrum
corruptum). The overall color is more yellow with
more obvious white spots on the abdomen and white
stripes on the thorax.

You can help understand this phenomenon. If you happen to observe a lot of dragonflies flying in the same direction (not in flocks like birds—it’s more like a stream) you can really make a contribution. At a minimum, a few minutes to record your observations and a few minutes to let someone know is all you have to do. If you want to put more into it, like formal counts, all the better.

These movements, when they occur, vary widely from pretty light (a few passing a fixed point per minute) to major (in the hundreds per minute) to exceptional (in the thousands per minute). When you’re observing a directional movement of dragonflies the best way to gauge their numbers is to look across a wide open area (like a beach, or an open dune area, or a parking lot) perpendicular to the direction of flight and count the number of individuals that pass your line of sight over a period of time—say five minutes. Divide the total count by the number of minutes to get the rate. It can be helpful to pick a landmark at the other end of your line of sight—a utility pole, a rock, a car, etc., and imagine a “finish line” between you and the landmark.

Additional information that is helpful include the date, location, the times that the flights start and stop (or at least the beginning and ending times of your observations), the direction of movement (determined with a compass, if possible), and general weather conditions—particularly wind direction. If you conduct formal counts like described above, include the length of your line of sight. Of course the species involved is important and if you are unsure of what you’re looking at, photos and video (even of distant subjects) are often helpful for identification later on. As I said earlier, the Variegated Meadowhawk is the primary species seen in directional movements at coastal Northwest locations and I have some photos of that species here and you can view a lot more at BugGuide.net.

Mature male Variegated Meadowhawks are largely red and brown on the body and the variegated patterning gives them a dusty orange appearance from a distance. Mature females tend to be more brown instead of red. Their wings are clear, but the major veins along the leading edge of each wing are orange which can be noticeable at close range. Immature, or more recently emerged, individuals are overall yellow or yellowish-orange with white spots on the abdomen and white stripes on the thorax—each white stripe on the side of the thorax terminates at a yellow spot. The veins along the leading edges of the wings are yellow instead of orange. As they mature, the white stripes and spots darken, but that pair of yellow spots on the side of the thorax persist.

A fully mature male Variegated Meadowhawk (Sympetrum corruptum) without any white spots or stripes.

This male Variegated Meadowhawk (Sympetrum corruptum) is intermediate in maturity still with white spots and stripes, but those are fading.

If you see a lot of Variegated Meadowhawks not flying, but just hanging around open coastal areas away from fresh water like parking lots, parks, and beach areas with drift wood, that’s worth noting too. It may be that a flight just ended and they are taking a break to rest and feed. Maybe the conditions that were good for a flight ended and they are waiting for the right time to start again. Again, recording the weather conditions during your observation may be very helpful.

Report Your Observations

So now that you have some information to share, what do you do with it? At the very least, report your information to an appropriate listserve so that it’s there for others to glean and perhaps combine with other reports. This also alerts readers when a flight may be going on in their area so they can make their own observations. For the northwestern US and western Canada report to the NW_Odonata Yahoo Group; in California it’s the CalOdes Yahoo Group. If you’re not a member of any of these listserves, find someone who is and have them post your information. You can let me know and I’ll make sure that your information ends up in the right place.

Some people collect observations in their local areas such as Mike Patterson (North Coast Diaries) in the Columbia estuary area of Oregon and Washington, and Range Bayer and Terry Morse in Lincoln County, Oregon. At the continental scale, Chris at The Dragonfly Woman is collecting reports of dragonfly swarms (both migratory and feeding swarms) from throughout North America. She has a handy web form where you can report your observations and help out with her research.

Research is also going on at the molecular level to figure out from which latitude, roughly, migrating Variegated Meadowhawks originate. There is a known correlation between the abundance of deuterium (a hydrogen isotope) in the tissues of dragonflies and the latitude where they lived as a nymph and emerged. This analysis, which uses one wing from each specimen, will give us some indication of how far these meadowhawks had traveled at the time they were collected. Dennis Paulson is accepting specimens of Variegated Meadowhawk for this research and he is interested in both recently emerged individuals from local populations and individuals which were part of a directional movement. Either dried or acetoned specimens can be used. He follows the listserves mentioned above so you can contact him that way, or just let me know and I’ll put you in touch.

So get out there and look for migrating meadowhawks. Anyone can make a contribution!

Postscript, 18 August 2011

Dennis Paulson reminded me that major Variegated Meadowhawk flights were also observed at San Juan Island, Washington and in the mountains of western Montana during 2010, so this phenomenon is not restricted to the outer coast. Naturally we’d like to hear about these flights wherever they are observed.

Dennis also elaborated on a Migratory Dragonfly Partnership, including representatives from Canada, the US, and Mexico that will be putting together materials and protocols to involve the public in recording and monitoring dragonfly migration across the continent. The deuterium analysis that I mentioned above is part of this project which is funded by the US Forest Service, through The Xerces Society for Invertebrate Conservation (based in Portland, Oregon). I’m sure we’ll be hearing more about that over the next year.

Now THIS is Recycling: Jumping Spiders Using Dragonfly Exuviae

2011-08-11T13:10:00.000-07:00

When dragonflies emerge and become adults they not only abandon their submerged lifestyle, but they leave behind a natural, albeit temporary, cavity clinging to some above-water surface like a plant, a log, a rock, or even just on the ground. This is their final exuvia—their ultimate nymphal (or larval, if you prefer) exoskeleton within which metamorphosis took place before emergence. These “skin suits” are, of course, biodegradable, but as long as the weather stays dry and it isn’t dislodged by wind, the exuvia can stay intact and in place for some time—possibly for weeks. Why let this little shelter go to waste?

A few years ago Tim Manolis discovered in California that the jumping spider Sassacus vitis uses these translucent cavities as roosting sites and nurseries. The ultimate in green housing! He has since found two other species using dragonfly exuviae: Sitticus palustris and the ant-mimicking Peckhamia (near americana), although the latter may not be a regular user. It turns out that this behavior was known in Europe although it doesn’t appear that it has been investigated very thoroughly. Tim seems to be the only person in North America that is really looking into this and he would love to be informed if you find exuviae being used by jumping spiders (you can contact me and I’ll relay your information to him).

How can you tell when a dragonfly exuvia is being used by a jumping spider? The two that I have found so far I discovered by accident: I collected exuviae and then later found little jumping spiders wandering around the interior of the vials. A closer look at the exuviae revealed silk “tunnels” descending into the abdomen from the opening on the thorax.

Silk threads on the outside of the exuvia may be a clue, but I imagine some silk may be left by non-occupants just passing through too. You may be able to peer into the exuvia through the thoracic opening and see the silk-lined interior and a big pair of jumping spider eyes peering back (or at least glimpse some other body part). If you can’t see into the interior of the exuvia, try looking at it with a light source (the sun or a flashlight) shining from the other side like in the photo below. The dark blob in the abdomen is a jumping spider.

The photographed exuvia below—a Spiny Baskettail (Epitheca spinigera) at Lake of the Woods, was the second one that I’ve found with a jumping spider in residence. Like I said above, I only realized it after I noticed the spider wandering around in the vial that was holding the exuvia. After a short stroll it crawled back inside and that’s when I took the photo.

The first time I found a spider-occupied exuvia, it was that of a Four-spotted Skimmer (Libellula quadrimaculata) at Camas Prairie in the northern Oregon Cascades earlier this summer. I sent that occupant to Tim Manolis and he determined it to be Sitticus palustris. I’m hanging on to my latest find to see if tiny spiderlings emerge—it takes about three weeks for eggs to hatch according to Tim, and this spider seems to be spending a great deal of time in the exuvia as though it was guarding a clutch. Once I see whether “jumplets” are produced or not, I’ll send the adult to Tim so he can determine the species.

So, if you happen to come across dragonfly exuviae, see if you can find spiders within. Tim Manolis wants to know about them—especially from areas outside of Oregon and California since he currently only knows about spider-occupied exuviae from those two states. Information he is interested in includes the dragonfly species that left the exuvia behind and whether any spider eggs are inside (i.e. was the exuvia used for roosting or for nesting). If you can ship the adult spider to him he’ll be doubly appreciative and include the exuvia if you don’t know which species it is. If you don’t know how to reach Tim, contact me and I’ll put you in touch.

Thanks to Tim Manolis for providing lots of helpful information used in this post, and to the fine folks at BugGuide.net for their web site.

Postscript

The spider eventually exited the exuvia and constructed a silk “hammock” in the vial. It turns out that it was a male using the the exuvia while molting. I sent the spider to Tim Manolis and it appears to be Sitticus palustris.

Lake of the Woods, Oregon

2011-08-08T21:38:00.000-07:00

Lake of the Woods is a large natural lake nestled in the southern Oregon Cascades within sight of the sleeping Mount McLaughlin. With easy access right off Hwy 140 and at almost 5000 feet elevation, it’s a popular summer retreat for hordes of campers, boaters, hikers, and day users of all sorts—a recipe which usually keeps me away, but there is a gem of a spot in the middle of it all which is great for odonates.

View Lake of the Woods in a larger map. The rectangle identifies Rainbow Bay.

The gem of a spot is at the easternmost shore of the bay on the eastern side of the lake. That’s Rainbow Bay, and there’s a sedge meadow there which is largely inundated when the lake is at its highest levels during spring and early summer, but becomes mostly dry by late summer and fall. A band of tules hugs the edge of the meadow in deeper water.

View Rainbow Bay in a larger map. The pin identifies the meadow.

This area is easiest to access from dirt pullouts on the side of Dead Indian Road where it passes at its closest. There is also a well-maintained trail that passes through here between the road and the meadow, and connects the Rainbow Bay day use area (to the north) with Sunset Campground (to the south).

This location is well known among Oregon odonatists as the only place in the state where Lance-tipped Darner (Aeshna constricta) can be found somewhat reliably, and I visited on 5 August 2011 in an effort to find nymphs and/or exuviae of that species. I was not successful, but there were plenty of other odonates around to keep me busy.

Things were definitely late up here, as they are all over the Northwest this year. That was most evident in the large number of Spiny Baskettails (Epitheca spinigera) still flying through the open forest around the meadow, and I even found one exuvia of that species still clinging to some vegetation. Normally that species is quite scarce up here by now. Lots of darners were feeding in a loose swarm over the area—three species were represented among the relatively few that I could catch, but the Lance-tipped was not one of them. Clouds of just emerged meadowhawks drifted up from the sedges as I wandered through them.

I haven’t tallied up the complete list of species found at the Rainbow Bay meadow, but below is what I recorded during a few hours on that recent visit. Following that are photos of several of those species taken that day.

Damselflies (Zygoptera)

Spreadwings (Lestidae)

Northern Spreadwing (Lestes disjunctus)
Emerald Spreadwing (Lestes dryas)

Pond Damsels (Coenagrionidae)

Boreal Bluet (Enallagma boreale)
Tule Bluet (Enallagma carunculatum)
Pacific Forktail (Ischnura cervula)
Western Forktail (Ischnura perparva)

Dragonflies (Anisoptera)

Darners (Aeshnidae)

Variable Darner (Aeshna interrupta)
Paddle-tailed Darner (Aeshna palmata)
Blue-eyed Darner (Rhionaeschna multicolor)

Emeralds (Corduliidae)

American Emerald (Cordulia shurtleffii)
Spiny Baskettail (Epitheca spinigera)

Skimmers (Libellulidae)

Chalk-fronted Corporal (Ladona julia)
Hudsonian Whiteface (Leucorrhinia hudsonica)
Eight-spotted Skimmer (Libellula forensis)
Twelve-spotted Skimmer (Libellula pulchella)
Four-spotted Skimmer (Libellula quadrimaculata)
White-faced Meadowhawk (Sympetrum obtrusum)
Striped Meadowhawk (Sympetrum pallipes)
Band-winged Meadowhawk (Sympetrum semicinctum)

Male Boreal Bluet (Enallagma boreale).

Male Emerald Spreadwing (Lestes dryas).

Male Spiny Baskettail (Epitheca spinigera).

Male Chalk-fronted Corporal (Ladona julia).

Male Hudsonian Whiteface (Leucorrhinia hudsonica). This one has atypically small red spots on the abdomen.

Female Twelve-spotted Skimmer (Libellula pulchella). Scarce in forested mountain areas.

Female Four-spotted Skimmer (Libellula quadrimaculata).

Male White-faced Meadowhawk (Sympetrum obtrusum).

Female Band-winged Meadowhawk (Sympetrum semicinctum) with quite a heavy load of parasitic water mites.

Snaketail Emergence Sequence

2011-08-02T15:23:00.000-07:00

A while back I posted a sequence of shots of an emerging American Emerald (Cordulia shurtleffii) which was quite popular. You can see that post here. I love emergence sequences, so here’s another one—this time a female Pale Snaketail (Ophiogomphus severus) in the family Gomphidae, or the clubtails. This was on the Burnt River in eastern Oregon a few weeks ago. Just like last time, I included the time stamp in the upper right corner (hh:mm:ss), so you can see how much time elapsed between each shot.

As usual, emergence was already well underway by the time I could take my first shot in the sequence. Unlike many other dragonflies, clubtails are able to emerge on a horizontal surface and they look kind of odd with only the abdomen still in the exuvia. In this position, I find it suggestive of a cobra rearing up and spreading its hood which seems rather appropriate for something called a snaketail. The white thread is a tracheal lining which stays attached to the exuvia so that it is pulled out of a spiracle (an opening to the tracheal network) during emergence. This allows her to get oxygen from the air now that she is out of the water.

While my attention was elsewhere for a couple of minutes, the abdomen was pulled entirely from the exuvia and she is supporting herself entirely on her legs now. Wing expansion is progressing rapidly.

The wings are pretty much at their full length now, but the abdomen still has some stretching to do.

Now the wings and abdomen are at full, or nearly full length, and the wings are almost totally clear.

My attention was elsewhere again for a few minutes and all that's left is the exuvia which I collected for the record.

Just a Photo: Spiketail Nymph

2011-07-18T15:00:00.000-07:00

I found this bad boy (bad girl, in fact) in a little stream in Oregon’s Blue Mountains a few weeks ago. It’s a full-grown nymph of the Pacific Spiketail (Cordulegaster dorsalis), the only Northwest representative of the family Cordulegastridae. You can’t tell from the photo, of course, but it’s over an inch long. She’s a chunk too—a little lotic tank. Nymphs of this species take five years to get to this size. If it looks dirty, it is—these guys are pretty hairy and all kinds of debris cling to them. These hunters live buried in fine silt and mud with only their eyes protruding so they can watch for prey. You can see what the adult Pacific Spiketail looks like here.

ID Challenge #2 Answer

2011-07-15T15:32:00.000-07:00

I intended to post an answer to ID Challenge #2 much earlier than this, but it just didn’t work out. I’ve been on a road trip to/from Fort Collins, Colorado (for the Dragonfly Society of the Americas annual meeting) and I didn’t have as much down time as I thought I would. During the down time I did have, I was, well… …down. Anyway, better late than never.

Click image for a larger version.

What we have is a rather plain-looking odonate with not a lot of obvious patterning. Let’s work this from the top down. Is it a dragonfly or a damselfly? We can’t tell how big this thing is, but it has a relatively long, slender build, the wings are slender and petiolate (narrowed at the base), and the wings are more-or-less parallel to the abdomen while in the closed position. This all indicates that we are looking at a damselfly. Even during those few times when dragonflies close their wings while perched (like during or right after emergence) the angle of their “hinges” puts the wings almost perpendicular to the abdomen, not parallel to it.

We can also see that this is a female since there is a curved ovipositor underneath the abdomen near the tip. All female damselflies have this sort of ovipositor (used to insert eggs into plant or other material), but only certain families of dragonflies have this kind of equipment.

We can narrow down the choices further if we take a close look at some of the little bits. There is a well-developed vulvar spine just in front of the ovipositor (“S” in the close-up at right). In the Pacific Northwest this eliminates genera like Argia (dancers) and Coeanagrion (Eurasian bluets). This is variable among the Ischnura (forktails)—even within some species.

Now let’s look at the legs. The spines on the tibiae (“T” in the close-up at right) are relatively short. Some genera like Argia (dancers) and Nehalennia (sprites) as well as species in Lestidae (spreadwings) have longer tibial spines—about twice as long as the spaces between the spines, so this feature eliminates those.

What’s left? Well, there are the Enallagma (American bluets), of which several species occur in the Northwest. Females of these species are more boldly patterned with black on the abdomen and thorax and they also tend to have conspicuously pale postocular spots on top of the head. But what if it’s an immature that isn’t displaying typical mature color/patterning? I always like to use structural differences whenever possible to be certain. We also haven’t eliminated the Ischnura (forktails) completely.

Look at that last image again, at the underside of the thorax. There’s an obvious bump there with coarse hairs on it. This points us directly to one genus that we haven’t even mentioned yet: Amphiagrion (red damsels). The vulvar spine and short tibial spines are consistent with this genus too. Amphiagrion is what we have.

The Pacific Northwest species is A. abbreviatum (Western Red Damsel), and females are quite variable both in color and patterning. Some are very dull like this individual, some are more brown or orangish, and some are male-like with a bright red abdomen and a mostly black thorax; some have less black patterning on the thorax, but more obvious black spotting on the abdomen. Whatever their color and patterning, all have that bump on the underside of the thorax which is very helpful.

Several commenters got this one right and I’m sure they spotted that bump. I think it’s important to know the little structural details which are far less variable than coloration and can help you identify confusing individuals like this.

ID Challenge #2

2011-07-01T10:00:00.000-07:00

Do you know what this is? If you’re not sure, it can be figured out with a bit of research. It is a species which occurs in the Pacific Northwest, so that should narrow it down substantially. Leave a comment to let me know what you think it is even if you’re not certain. Comment moderation will be turned on until I post the answer, so they will not be visible in the mean time.

Postscript, 15 July 2011

This challenge is now closed. The answer with a complete discussion is here. If you missed ID Challenge #1, be sure to check that out too.

A Great Day for Emergence at Camas Prairie

2011-06-24T20:06:00.000-07:00

I just returned from a visit to Camas Prairie, Oregon, which is a little ways south of Mt. Hood in the Cascade Mountains. The prairie is a large wet meadow and great for a lot of montane odonates in the Pacific Northwest. Because of the late spring-like (cool and wet) conditions in the region, I didn’t expect much activity at Camas Prairie, but emergence of several species is well underway.

View Larger Map

There were lots of adults of four species: of the dragonflies, Four-spotted Skimmer (Libellula quadrimaculata) and Hudsonian Whiteface (Leucorrhinia hudsonica); of the damselflies, Western Forktail (Ischnura perparva) and Western Red Damsel (Amphiagrion abbreviatum). The skimmer and whiteface were emerging in large numbers as well...

A female Four-spotted Skimmer emerging. Note the exuvia (shed nymphal skin) at the base of the sedge stem.

An emerging female Hudsonian Whiteface still holding on to its exuvia. Another one is in the background to the left.

I never saw any darners flying around, but obviously many have emerged recently as indicated by the numerous exuviae in the water. Several Canada Darners (Aeshna canadensis) were in the process of emerging. That species is one of the earlier of the montane darners to make an appearance and I assume most of the abandoned darner exuviae belong to them...

On left, two darner exuviae are floating on the water surface. On right a female Canada Darner is almost done emerging.

I was surprised to find a Subarctic Darner (Aeshna subarctica) emerging. Within Oregon, this species is known from only a few sites in the Cascades south of Mt. Hood, but it is most abundant at Camas Prairie. The earliest known flight date for the species in Oregon was 27 July, however, so this is more than a month earlier.

An emerging male Subarctic Darner clinging to its exuvia.

Another surprise was an emerging Brush-tipped Emerald (Somatochlora walshii) which beat the previous earliest flight date of 6 July in Oregon.

On left, an emerging male Brush-tipped Emerald clinging to its exuvia. The same individual on the right after it was carefully relocated in order to collect the exuvia. You can just make out the "brushes" on the tip of the abdomen.

Alvord Basin Weekend, 17–19 June 2011

2011-06-22T18:19:00.000-07:00

I spent last weekend (17–19 June) in the Alvord Basin of southeastern Oregon to check out the odonate action with several friends. This is a stunning area of wide-open high desert vistas below the humbling east face of Steens Mountain and it’s a special area for odonates. Several species reach their northern or northwestern limit at wetlands associated with hot springs in this area. In particular we visited Mickey Hot Springs, Alvord Hot Spring, Borax Lake, and Twin Springs, but only Mickey Hot Springs had any appreciable activity. At most of these hot springs, the water is too hot to support insect life where it leaves the ground, so follow the little streams to wetlands where the water has cooled sufficiently.


The "top" pool at Mickey Hot Springs. Sometimes you see odonates ovipositing here, but I'm sure it's too hot for eggs/nymphs to survive.

Boiling water is leaving the ground further downslope—way too hot!


Just right! Eventually water drains into this well-vegetated wetland. By the time it gets here, the water has cooled enough to support all sorts of life.

Within Oregon, the Alvord Basin is the only area where Bleached Skimmer (Libellula composita), Comanche Skimmer (L. comanche), and Red Rock Skimmer (Paltothemis lineatipes) are known, and Oregon’s first Desert Forktail (Ischnura barberi) was found here just last year. Some other “specialties” of desert wetlands in Oregon’s corner of the Great Basin include Hoary Skimmer (L. nodisticta), Desert Whitetail (Plathemis subornata), Paiute Dancer (Argia alberta), and Black-fronted Forktail (I. denticollis).

It’s been a very cool, wet spring all over the Pacific Northwest and it is just as evident—if not more so, in this normally arid basin where the average annual precipitation is about eight inches. All of the seasonally wet lakes and streams that are typically dry this time of year (or entirely dry some years) are full of water. The Alvord Desert—a dry lake bed of about 80 square miles was full of water right up to the brim. I’ve never seen that before. Steens Mountain was especially impressive for this time of year with lots of snow still clinging to its craggy eastern face (photo above).

The odonate activity was certainly anemic for this time of year. There were quite a few damselflies out, but not many dragonflies. Of the “specialties”, we saw only a few Bleached Skimmers, a couple Hoary Skimmers, and several Desert Whitetails. The widespread Western Pondhawk (Erythemis collocata) was fairly numerous and there were several Variegated Meadowhawks (Sympetrum corruptum), but we saw only a couple of darners (likely California Darner, Rhionaeschna californica) cruising the wetlands. Paiute Dancer, Black-fronted Forktail, and Western Red Damsel (Amphiagrion abbreviatum) were out in good numbers and there were scattered Western Forktail (I. perparva) and Pacific Forktail (I. cervula). We did not see a single bluet (Enallagma), however, which seemed very strange.

Below are a few odonates photographed at Mickey Hot Springs.

A male Paiute Dancer (Argia alberta).

A male Black-fronted Forktail (Ischnura denticollis).


An immature male Bleached Skimmer (Libellula composita). With maturity, the abdomen and thorax will be covered with pale bluish-gray pruinescence and the eyes will turn pearly gray.

A male Desert Whitetail (Plathemis subornata)—again an immature. As he matures, the abdomen will
become covered with white pruinescence and the two zig-zaggy dark bands on each wing will coalesce
into a singe wide band.

Another Desert Whitetail, but a female this time.

In another week or two, there ought to be a lot more more dragonflies including additional species. It’s worth the trip!

John Day River Outing, 11 June 2011

2011-06-12T20:33:00.000-07:00

On Saturday I decided to head east and see how the odonate action was on the John Day River in north-central Oregon. I wasn’t very hopeful since it has been such a late season this year in this region, and I figured the water level would be pretty high (the Columbia River has been at near flood stage for weeks now), but I wouldn’t find out if I didn’t look! I went to the Cottonwood Recreation Area (still labelled J.S. Burres State Park on many maps) at the Hwy 206 crossing—one of my favorite odonating places in the state. The John Day River is in a deep, rugged canyon over much of its lower 120 miles or so, and this is one of the few places where you can access it by car along this stretch.

View Larger Map

The water level was high which made the shores pretty much unworkable, but there were quite a few Sinuous Snaketails (Ophiogomphus occidentis) hanging out in the surrounding sagebrush. It was rather breezy while I was there, and for some reason that always seems to make dragonflies more skittish and difficult to approach (or maybe I’m just looking for something to blame when I scare them off before I can get a shot). This male cooperated for just enough time to get a nice image…

…and this female perched at a weird angle, but she gives us a nice view of her striking abdomen…

There really wasn’t much else around except for one or two California Darners (Rhionaeschna californica) that made an occasional appearance over the sagebrush. I didn’t see a single Emma’s Dancer (Argia emma) which was really strange since it is normally such a common species here. I can’t help wondering if they’ll ever emerge this season if they haven’t done so already.

Before I headed elsewhere I checked the river shallows (what I could access without getting swept away in the current!) and I turned up one nymph of the snaketail. Its swollen wing pads indicate that it is close to emerging to join its cohorts in the sage…

Notice the thick, club-like antennae in front of the head which are characteristic of clubtail (Gomphidae) nymphs (and compare with the darner nymph below).

I drove a few miles up out of the canyon to a little stream choking with cattails and watercress. There were quite a few Vivid Dancers (Argia vivida) including this copulating pair…

I also checked for nymphs here and came up with a Paddle-tailed Darner (Aeshna palmata )…

On my way home I stopped at Bass Lake in North Bonneville, on the Washington side of the Columbia River. I recently learned that Pacific Clubtails (Gomphus kurilis) were found here a couple of years, so I gave it a check.

View Larger Map

The Pacific Clubtail is only known from two other locations in the state—one of them just a few miles east of North Bonneville. I had no trouble finding them at Bass Lake—about eight or nine, catching the late afternoon sun on the gravel trail that goes from the parking area to the lake. They were mostly quite approachable too…

The species count for the day was really low, but this was a great way to end it.

Just a Photo: A Table for Eight, Please?

2011-06-09T18:39:00.000-07:00

I figured readers would enjoy this photo. Here we have four pairs of Vivid Dancers (Argia vivida), all ovipositing in tandem on the same sprig of emergent vegetation at Gold Lake, Oregon. I can just imagine the males discussing the issues of the day over cold brews while the females are busy depositing their eggs. It’s not unusual to find multiple pairs of a species ovipositing in close proximity like this, but I don’t think I’ve ever seen a group “seated” so nicely.

On a more technical note, what you’re seeing is an instance of contact guarding—the mated male remains in tandem to the female while she’s depositing eggs in order to prevent other males from coming along and removing or displacing his sperm (it’s safe to assume that each of these pairs copulated before they all found this great piece of real estate). Contact guarding is common among the damselflies (coenagrionids and lestids, anyway), but is more limited among the dragonflies where it is chiefly performed by some libellulids (skimmers), as well as the Common Green Darner (Anax junius).

A Few Ecuadorian Odonates

2011-06-06T18:55:00.000-07:00

I haven’t posted anything here for a while since I started preparations for a trip to Ecuador and the Galapagos Islands. I intended to publish something right before I left and have another post scheduled to publish while I was gone in order to keep the content flowing, but things just got too hectic.

This wasn’t a dedicated odonate trip like I’ve done before—it was more of a touristy, relax and enjoy the culture, see some new places and wildlife sort of trip. I’ve been to the Ecuador mainland before, but this was my first trip to the Galapagos and it was a blast!

Naturally, no matter where I go I’m on the lookout for odonates, and this trip was no exception. I didn’t see very much, however. The mainland weather was rather cool (relatively) and cloudy much of the time, so there just wasn’t a lot flying. I saw a couple of species flying about the scrub on the Galapagos Islands—species that are strong fliers which are able to set up shop on distant oceanic islands, so these were on the mainland too and didn’t really get my juices flowing. I never got to any freshwater wetlands on the islands where there might be more interesting odonates.

While on the mainland, things came together for a few hours one morning in the Zamora area: lots of forest, lots of beautiful streams, and some glorious, radiant sun. This gave me an opportunity to find and photograph some really interesting odonates on the Amazon slope of the Andes. Here are a few . . .

Argia sp.

Argia is the most speciose genus of damselflies in the New World, and they are at their most diverse in the tropics. The problem is that the tropical species, particularly in South America, are in serious need of a revision (which is apparently underway). Some species are pretty straightforward and well understood taxonomically, some are rather confusing (and may be complexes of multiple species), and there are a number of species which are known, but not yet described. On top of all that, there are certainly more species which are yet to be discovered.

There were a number of individuals of the Argia above, with the mostly dark abdomen and brown humeral (or “shoulder”) stripe on the thorax. They were mostly around small, rocky, sun-dappled streams (often with a little waterfall) under forest canopy. It may be A. gerhardi, or maybe it’s one of those known, but not yet described species, or maybe it’s something totally new.

Polythore terminata

Polythore terminata is a large, conspicuous, and fairly common species of forested streams in the Zamora area. Males (like the individual above) are distinctive with their black tips on otherwise clear wings (like they were dipped in ink). I love the black thorax with white pin stripes. On females, the black on the wings don’t quite make it all the way to the tips.

Philogenia sp.

The Philogenia are real shade lovers and this guy was hanging out under a canopy of leafy vegetation near a small waterfall stream. This is a damselfly, but like most members of its family—Megapodagrionidae, they perch with their wings wide open. This species is pretty typical of the genus with its dull earth tone coloration except for the conspicuous patch of nearly white pruinescence near the tip of the abdomen. I don’t know which species it is, however. I thought it might be P. redunca, but the abdominal appendages are clearly wrong. It may be undescribed.

Archaeopodagrion armatum

This was only the second time this species has been seen alive. Ken Tennessen and I first discovered it in 2008 and we published the description in 2010. It was fun to go back and find them flying very close to the location of discovery (within about a hundred yards, actually). There are only two other species of Archaeopodagrion known—both from Ecuador, described by Clarence Kennedy in 1939 and 1946. One of them was not seen again until just a few years ago (A. bicorne) and I think the other still has not been refound (A. bilobatum). It was quite a shock to find a third species of this mysterious genus.

I saw several individuals along a little trickle of water that flowed on a section of trail just before it joined a small stream below a waterfall. Like the Philogenia above, this is a real shade lover. The only time I saw individuals out in the open flying above the trickle of water was when the sun was hidden by clouds. When the sun was out, they disappeared. During one of those sunny moments, I lifted a large leaf and found an individual perching back in the dark, safely protected from UV rays.

Also like the Philogenia, Archaeopodagrion is a damselfly in the family Megapodagrionidae and perch with the wings wide open. Archaeopodagrion is even more cryptically colored with it’s earth tones and a bit of dull yellow patterning. This species in particular has conspicuous “flaps” on the prothorax (you can just make out one behind the right eye). The male’s abdominal appendages are pretty unusual too. If you’d like to see the description, you can view a PDF here.

I hope this whet your appetite for tropical odonates which are extremely interesting and very much in need of greater understanding. A previous post profiled the stunning Zenithoptera lanei and I’ll occasionally write about other tropical odonates that I have encountered during my travels. They’re not in “my” Pacific Northwest, but Ecuador is in northwestern South America!

Identification: Dragonflies versus Damselflies

2011-05-09T09:54:00.000-07:00

I’ll be posting periodically on odonate identification and right at the top—dragonflies versus damselflies, is a natural place to begin. As usual, I’ll be using the term “dragonfly” (and the plural “dragonflies”) in the strict sense meaning only odonates in the suborder Anisoptera, excluding damselflies which are in the suborder Zygoptera. For a refresher on these terms, see my post Is that a Dragonfly or an Odonate?

Generally speaking dragonflies and damselflies really aren’t all that similar, but it’s useful to have a good fundamental understanding of the features that differentiate them. At the very least you can impress your friends, right? So below are the features that will tell you whether you’re looking at a dragonfly or a damselfly in roughly the order of the bigger, more obvious to the itty parts that require closer scrutiny. I mostly cover adults since that’s what most people see, but I’ll talk about nymphs a bit at the end.

I primarily have the odonate fauna of the US and Canada in mind as I write this post, but these differences work for much of the rest of the world. There are some groups in other regions which don’t fit one or more of these criteria, but I’m going to keep this simple and not worry about them at this time.

Overall Build: Dragonflies are more robust and chunkier than damselflies. This is especially noticeable in the abdomen which is very thin on damsels relative to their overall length. Also notice the ratio of the abdomen length to thorax length which is greater on damsels. There’s a reason why John Acorn’s book Damselflies of Alberta was subtitled Flying Neon Toothpicks in the Grass—damselflies are thin.


On the left a dragonfly—Twelve-spotted Skimmer (Libellula pulchella), and on the right a damselfly—Boreal Bluet (Enallagma boreale). Not to scale. Compare their build and wing positions.

Wing Position: Dragonflies perch with their wings open, either straight out to the sides or drooping to some degree. A common exception to this is right after a dragonfly has emerged—check out the final images of my post A Dragonfly Emergence Sequence with a series of shots of an emerging dragonfly. Damselflies most often perch with their wings closed above the abdomen, or partially open. Even when damsels perch with the wings open, as some do on a regular basis, the wings are not open to the same degree that dragonflies open their wings.

Wing Shape: The fore- and hindwings of damselflies are essentially identical in shape, while on dragonflies the hindwing is noticeably more broad, particularly near the base.

On the left a pair of dragonfly wings, and on the right a pair of damselfly wings. Forewings above; hindwings below. Not to scale. Note that the dragonfly's hind wing is clearly more broad than its forewing; the damselfly's wings are virtually identical in shape.

Head/Eye Shape: Damselflies are hammer-headed—the eyes cap the ends of the relatively wide, almost dumbell-shaped head. One of my first posts, Damselflies have a good head on their shoulders, was about how the shape of the damselfly head can be beneficial. Dragonfly eyes are more variable—some have a gap between the eyes, on some the eyes meet at a point on top of the head, and on some the eyes meet at a seam over the top of the head. Even when there is a space between the eyes on top of the head of a dragonfly, that gap is no wider than the width of either eye while the gap is more than the width of either eye on damsels.

On the left two dragonfly heads, and on the right a damselfly head with the eyes colored green. Not to scale. The views are from the top. In particular compare the gap between the eyes on the lower dragonfly and the damselfly.

Clasping Point: By this I mean where the male holds on to the female while in tandem and copulating. Female dragonflies are clasped at the back of the head between the eyes; female damselflies are clasped near the front of the thorax

On the left a female dragonfly (Red-veined Meadowhawk, Sympetrum madidum) is clasped by a male at the back of the head. On the right a female damselfly (Spotted Spreadwing, Lestes congener) is clasped near the front of the thorax. Not to scale.

Male Abdominal Appendages: Copulation between male and female odonates can only occur when males clasp females with their abdominal appendages. The difference between male dragonflies and damselflies is in which structures are developed into clasping equipment. In both cases, a pair of structures called cerci (singular = cercus) are used. On dragonflies, the epiproct is also developed for this purpose, while on damselflies it is a pair of paraprocts. The result is that dragonflies have a total of three abdominal appendages—two upper and a single lower (two cerci + one epiproct); damselflies have a total of four abdominal appendages—two upper and two lower (two cerci + two paraprocts).

The nymph of a dragonfly, Eight-spotted Skimmer (Libellula
forensis). Note the short, spiky appendages at the end of the
abdomen (on the left).

Nymphs: The nymphs (or larvae if you prefer) of dragonflies and damselflies are pretty different. Very much like the adults, dragonfly nymphs are more robust, chunky beasts while damselfly nymphs are more slender and delicate looking. Besides overall shape, the primary structural difference to look for is at the rear end—dragonfly nymphs have simple, short, spiky appendages (technically, the cerci, epiproct, and paraprocts) while damselfly nymphs possess three relatively long, leaf-like external gills (technically, the middle gill is a strongly modified epiproct and the lateral gills are strongly modified paraprocts; they have cerci too, but these are tiny compared to the gills and require close scrutiny to see).

Dragonfly nymph gills are located within the abdomen and respiration is accomplished by pumping water in and out rectally (leading to jokes about bad breath). This also provides a mode of predator evasion in the form of “jet propulsion” when they forcefully expel water from the abdomen. Since the gills of damselflies are largely located externally on the leaf-like appendages, they don’t have jet propulsion. But they do use their gills like flippers to propel them fish-like through water.

Damselfly nymphs actually look more like some other aquatic insects than they do dragonfly nymphs. The Dragonfly Woman discussed how to differentiate damselfly nymphs from mayfly and stonefly nymphs. Above is an image of a dragonfly nymph; I don’t have any decent shots of damselfly nymphs yet, but check out The Dragonfly Woman’s link above for one.

A Dragonfly Emergence Sequence

2011-05-04T14:45:00.000-07:00

While on the southern coast of Oregon last weekend I checked a pond in Bandon for odonates to see what was flying. There were lots of Pacific Forktails (Ischnura cervula) and a few Tule Bluets (Enallagma carunculatum) flying, but no dragonflies. However, I did come across two American Emeralds (Cordulia shurtleffii) that were in the process of emerging. Below is a sequence of shots of one of them which I took periodically while I also looked for nymphs in the water. I included the time stamp in the upper right corner (hh:mm:ss), so you can see how much time elapsed between each shot.

Emergence was well underway by the time I found this individual. The nymphal skin split over the
top of the thorax where the head and thorax squeezed out. The legs and compressed wings are
exposed. The white threads are tracheal linings. They remain attached to the exuvia and are pulled
out as the thorax is exposed to open up the spiracles and facilitate the transition to air breathing. At
this point she is only supported by her abdomen which is partly still in the exuvia. This yogic
“bent over backwards” position is common among dragonflies at this stage of emergence.

While I was distracted, she used her now hardened legs to pull the rest of her abdomen out of the exuvia.
Wing expansion is well underway.

The wings are just about fully expanded and they are losing some of their opaqueness.

The abdomen is lengthening more noticeably now.

The wings are much clearer and the abdomen is just about there. Parts of the thorax are starting to turn
metallic green, particularly along the sutures.

I wasn’t able to stick around much longer, so I carefully transferred her to another perch and collected the
exuvia. During emergence and for a short time immediately after is the only time that you’ll see a dragonfly
perch with its wings closed over the thorax/abdomen like you see here. I imagine she was here for another
half hour or more before taking her maiden flight.

This was the first winged dragonfly that I’ve seen this season—in other words an adult, and it seems particularly fitting that she was in the process of emerging when I found her. I’m ready for more . . .

Just a Photo: What I dug up the other day

2011-04-24T17:20:00.000-07:00

Here are four dragonfly nymphs (or larvae if you prefer) that I dug up yesterday at Ice House Lake,
Washington. The big spiny one at upper left is a Spiny Baskettail (Epitheca spinigera), the little guy
below that is a young Common Whitetail (Plathemis lydia); going right, the big dark one near the
middle is a Libellula (probably Eight-spotted Skimmer, L. forensis); and the little one at far right is
either a meadowhawk (Sympetrum) or a whiteface (Leucorrhinia)—I didn’t keep track of which
nymph was photographed here and I can’t tell which it is from the photo.

A One Species Day, 22 April 2011

2011-04-22T18:26:00.000-07:00

With a weather forecast of sunny skies and a high in the lower 60s, I thought I’d get out to a couple of wetlands in the area of Battle Ground, Washington, that I’ve never visited before and see what they were like. I expected to see Pacific Forktail (Ischnura cervula), and I hoped to scrounge up something else—but didn’t. With this being a late spring, I can imagine all sorts of odonate nymphs just itching to pop out. They need more time obviously.

Here are a couple of Pacific Forktail images from today. None were completely mature, but a couple of the males were close—only the eye color wasn’t quite there yet. Note that the eyes are brown and gray instead of black and green.

One interesting male had the smallest dorsal thoracic spots that I ever recall seeing. They were so small that I first thought the top of the thorax was entirely black. Here’s a close-up to compare with the male above:

Technically it was a two species day since I flipped over a piece of lumber that was floating in a pond and I found this little darner (Aeshnidae) nymph. The little guy was only about a half-inch long, so it has a lot of growing to do before it emerges.

You can see how short the wing pads are (on top of the thorax just ahead of the base of the abdomen)—when it’s close to emerging the length of those will be at least the width of the head. It’s probably an Aeshna, the common species in the area being Paddle-tailed Darner (A. palmata) and Shadow Darner (A. umbrosa). I don’t expect to see adults of those species until July at the earliest.

It’s supposed to be warmer tomorrow (70°F!) and maybe I can get out again and find something else flying.

ID Challenge #1 Answer

2011-04-19T09:33:00.000-07:00

You can see the original challenge with full-size image here. Let’s take a top-down approach to figuring out this thing. To me this means first determining whether it’s a dragonfly (suborder Anisoptera) or a damselfly (suborder Zygoptera), then determining the family, and so on.

The identification of this odonate comes down to wing venation (obviously!), but first let’s look at the overall shape of the wings. Is either the forewing or the hindwing noticeably wider than the other? Yes, the hindwing is distinctly broader than the forewing, particularly near the base. This means that we are looking at a dragonfly, not a damselfly. The fore- and hindwings of damselflies are relatively narrow and virtually identical in shape to each other. The fact that the wings are held almost straight out to the sides also supports our conclusion that this is a dragonfly rather than a damselfly. Most damselflies perch with the wings closed, and those which tend to keep their wings open don’t typically hold them all the way out to the sides like this (not in North America, anyway).

Close-up of the wing bases with the anal loops
colored in green.

Next, let’s look at a feature of the hindwing venation known as the anal loop. It is partially obscured on both hindwings, but we can see more than enough to help us out. On this individual, the anal loop is clearly foot-shaped with a “heel” at the bend and ending at a “toe” near the hind margin of the wing. This foot-shaped anal loop points us directly to the family Libellulidae, a.k.a. skimmers. Dragonflies in other families have anal loops which are more semicircular or elongated (but not distinctly foot-shaped), or they may have no obvious anal loop at all. Conversely, there are some libellulids which don’t have the classic foot-shaped anal loop, but these are not typical of the family. You can assume that any dragonfly with an obviously foot-shaped anal loop is in the family Libellulidae and that’s what we have. [Geek speak: This assumes the taxonomy which has Macromiidae and Corduliidae at the family level separate from Libellulidae. Some authors place them within Libellulidae as subfamilies, Macromiinae and Corduliinae, alongside Libellulinae. In the latter taxonomy, the foot-shaped anal loop would indicate the subfamily Libellulinae.]

Close-up of the left forewing tip with the cell
adjacent to the posterior edge of the pterostigma
colored in green.

So where do we go from here? The pterostigma (the large darkened cell near the tip of each wing) is an obvious feature, but it’s pretty average looking (not very short, nor very long relative to its width), so that doesn’t really help a lot. It does rule out certain genera like the whitefaces (Leucorrhinia) which have relatively short pterostigmas (length to width ratio of about 2:1), but this doesn’t narrow down our choices very much.

Now look at the row of cells adjacent to the posterior edge of the pterostigma. This is unusual. Nearly all dragonflies have two or more crossveins adjacent to the pterostigma in the row right behind it, but not this one. There is only one crossvein adjacent to the pterostigma which is near the outer end, and there isn’t another crossvein for a little ways toward the inner part of the wing. That produces quite a long cell—about 50% longer or more than the pterostigma. This feature alone points us to the genus Pachydiplax which is handy because it contains only one species—P. longipennis or the Blue Dasher, a widespread species over much of the US and southernmost Canada.

So let’s lift the veil and take a look at the original unaltered image . . .

Male Blue Dasher (Pachydiplax longipennis) at Ice House Lake, Washington.

Now we can see that the abdomen is almost totally covered with pale blue pruinescence, there are short dark streaks enveloped in amber patches at the wing bases, and the eyes are bluish-green—all features of the Blue Dasher. Some individuals also have the diffuse amber patches on the outer half of the wing like this one does (most apparent on the left forewing). The identification of this guy (and it is a male) would have been a lot easier with the whole picture, but it becomes easy to forget about the little details which make identification straightforward in less than optimum circumstances.

Because of its continental range, its local abundance, and its approachability, the Blue Dasher is one of the most photographed odonates among nature photographers. I’ve seen a lot of photos of this species that were backlit (for the aesthetic touch), but the photographer didn’t know what species it was. In those conditions the wing venation is often very easy to discern. More than once I have found severed Blue Dasher wings (presumably left behind by a predator) which were quite easy to identify because of the features mentioned above.

I hope you found this challenge fun and informative. Above all else, this was really a demonstration of what can be done with venation alone. Learning odonate venation isn’t very easy—especially remembering the names (and there’s more than one naming convention too!), but I think it is interesting and rewarding. I recommend that you start with the more obvious features (like pterostigma, nodus, triangles, anal loop) and branch out (pun intended) from there. Any good field guide or manual to the odonates will have illustrations of the wings that identify the important veins, cell groups, and other features.

I consider this a test run of additional ID challenges that I plan to post on a regular basis. I will vary the difficulty level—some easier, some tougher—but it can be difficult to judge how challenging something like this will be for others (most of whom I’ve never even met). Using the submitted comments as a gauge, I’d have to say that this was a difficult challenge. I heard from four people, all of whom were correct, but I think that’s low compared to the total number of page views. I would like to engage more readers with these challenges and I hope I am more successful next time. Until then . . .

ID Challenge #1

2011-04-15T16:00:00.000-07:00

I always encourage others to send me their photos (or links to their online photos) of odonates that they have trouble identifying. The tougher ones force me to focus on the little details that often go unnoticed and I really enjoy the challenge. Here’s one for you...

Obviously, this image has been altered. It has been converted to black-and-white and I flattened out the mid-tones to obscure any color patterns that would make the identification more obvious. Also the body and basal portions of the wings have been cloaked by a dense fog for the same reason. I boosted the contrast on what’s left to make the wing venation pop out a little better. I cropped out the ends of the right pair of wings in order to enlarge the left pair (there’s nothing over there that you can’t see in the left pair of wings anyway).

This identification is really about the venation, and this individual can be identified to species pretty easily if you know what to look for. This is a fairly common species in the Pacific Northwest, and it is not restricted to this region. I suspect that many readers will not know what it is, but there’s nothing wrong with that. I hope it will be an interesting and educational experience once the answer is posted.

Post a comment with your answer. Even if you’re unsure of the identity, I’d like to hear from you anyway. In about a week, I’ll post a follow-up with the answer. In the mean time I will switch on moderation of all comments, so they will not appear on the blog until I post the answer.

Have fun and good luck!

Postscript, 19 April 2011

This challenge is now closed. The answer with a complete discussion is here.

Things that are NOT Damselflies

2011-04-11T06:32:00.000-07:00

Dragonflies (suborder Anisoptera) are distinctive enough that other insects are never confused for them. Okay, it probably has happened, but it must be pretty rare and I can’t think of any other insects that are even superficially like them. In fact, I’d guess that more often dragonflies are mistaken for other insects such as butterflies. The Halloween Pennant (Celithemis eponina) of eastern North America and the Filigree Skimmer (Pseudolean superbus) of the American Southwest are probably the most butterfly-like odonates on the continent with their boldly patterned wings (black-and-orange on the former, largely black on the latter). I have witnessed Zenithoptera of the Neotropics being mistaken for butterflies (see a post about Zenithoptera lanei here).

Damselflies (suborder Zygoptera) are different. There are other groups of insects with a similarly slender build and long, narrow wings. As you continue reading keep in mind these damselfly characteristics which, collectively, rule out these other insects:

often brightly colored (most often with blue), except for tenerals/immatures and many females
antennae inconspicuously short and very thin
two pairs of wings (although difficult to tell when closed over the abdomen)
legs relatively short and thin
very agile fliers, including hovering

Here are three groups of insects which have, in my experience, been mistaken for damselflies:

An adult antlion on the John Day
River, Oregon.

Antlions (Order Neuroptera, Family Myrmeleontidae): I suspect that a lot of people don’t know what antlions look like, or even realize that the adults are winged insects. The larvae are well known for building little funnel-shaped pits in sandy soil where they wait just below the nadir for their prey to fall in within range of their impressive mandibles. There’s no mistaking an antlion larva as an odonate, but the adults are rather damselfly-like with long, skinny abdomens and narrow wings.

The easiest way to know that you’re looking at an antlion is the presence of long, stout, almost comical antennae which curve a little bit at the tip. These are very different from the short hairlike antennae of damselflies. Just like damselflies, antlions possess two pairs of wings, but they are often finely speckled with dark pigment which is something you don’t see on damsels. Adult antlions are also typically nocturnal unlike damselflies, but I have scared them up from brush during the daytime. And they are very weak fliers compared to damsels. When I flush antlions during the day, they seem to fly in any random direction until they “crash” into another perch. Damselflies are far more agile and graceful on the wing.

Of the non-damselflies discussed here, the antlions are most similar to damsels. The Dragonfly Woman even devoted a couple of posts relevant to the topic: one on their similarity and how to tell them apart here; and another one here on artwork which is supposed to depict dragonflies or damselflies, but frequently depict antlions instead (this bugs me too).

A large crane fly in Vancouver, Washington.

Crane Flies (Order Diptera, Family Tipulidae): Many species of crane flies are generally large with relatively slender abdomens and wings. I don’t know a whole lot about these insects except that a couple of large Old World species have become established in the Pacific Northwest as lawn pests, and the large adults (up to 25 mm in length) are often seen around porch lights. There are many native species too which are often associated with wetlands.

One feature of crane flies which distinguishes them from damselflies right away is their very long, very thin, gangly legs. In fact, in the UK and Ireland crane flies are commonly known as “daddy long-legs”, a name often used for long-legged arachnids in the US and Canada. Also, like all Diptera, crane flies only have one pair of wings—the rear pair evolved into the small, knobbed halteres, and the bigger crane flies frequently perch with their wings open which makes it easy to see that there is only one pair. Something else to look for is the elongated “snout”—something you’ll never see on a damselfly.

Robber Flies (Order Diptera, Family Asilidae): These diverse predatory flies are, for the most part, not easily confused with damselflies. However, I have seen the relatively large and slender Efferia (in the Pacific Northwest, fairly common in arid areas east of the Cascades) mistaken for damselflies. Just like the crane flies, these have only one pair of wings but it’s difficult to tell because they usually perch with the wings closed.

A robber fly, Efferia, with prey on the John Day River, Oregon.

Robber flies are pretty husky compared with damselflies and their legs are relatively long and robust (great for grasping prey). Also notice how hairy this thing is, especially on the face and legs. Damselflies do have some hair too, but it usually requires a pretty close look to see it and they never appear furry like this Efferia does. If you get a close look at any robber fly, you may also see a stout, beak-like proboscis which is for puncturing and sucking out the contents of their prey. Odonates have chewing mouthparts—never a beak-like structure. One more difference is that these large robber flies are noisy fliers—very buzzy. Damselflies, on the other hand, are essentially silent fliers.

While browsing through some robber fly images in preparation for this post, I came across the genus Leptogaster which appear to mimic damselflies. I’ve never seen one of these and judging from the image details at BugGuide.net, it appears that the genus does not occur west of the Rockies. Check out these images at BugGuide.net for yourself. These still have relatively long, beefy legs typical of most robber flies quite unlike the legs of damselflies.

So, with a good look at one or two details, you should not confuse any of these non-damselflies with real damsels. These are all interesting insects, and I think they deserve to be recognized for what they are, even if they aren’t odonates—my favorite insects, of course. Can you think of any other insects which are, or could be, mistaken for damselflies (or dragonflies for that matter)?

My first flying odonate of the year! (and a bunch of other things)

2011-04-08T18:54:00.000-07:00

In my previous post about the Pacific Northwest’s first fliers, I lamented about the cool, wet spring that we’ve been having, and about not seeing any odonates yet. The forecast for today was sunny skies and highs approaching 60° F—still chilly for this time of year, but promising, so I checked out a wetland mitigation/storm water retention site in Vancouver. It isn’t what I consider a great place for odonates, but it’s convenient for a local excursion.

There were no flying odonates evident as I walked through the weedy/brushy margins of the site where I imagined recently emerged dragonflies and damselflies would be hanging out to feed and soak up the rays. There were a lot of other flying insects though. The Diptera (two-winged flies) in particular were out in force and had me wishing that I knew more about them. The most interesting among them was some sort of small robber fly (Asilidae) that I had never noticed before. These things have a really long proboscis relative to the body size which gives them a rather comical look. There were a lot of them and most that I looked at closely were feeding on some other insect. There was also amorous behavior going on. Here’s a series of shots of the robber fly. Leave a comment if you happen to know what it is. [I was informed by a couple of readers that these are not actually robber flies—be sure to see the postscript down at the bottom.]

I presume this is a male of the mystery robber fly.

This one shows the proboscis better.

I think this is a female. This one is enjoying the blooming Oregon-Grape.

A male robber fly with prey.


Now this I think is simply comical. Here’s a pair of the mystery robber fly copulating while the female is grasping (and I assume feeding on) a prey bug. I’m also impressed with the male hanging from his front legs. I won’t comment any further...

Here are some other dipterates that were enjoying the sun...

A bombyliid on the left and a syrphid.

And some sort of wasp...

And a couple of non-avian vertebrates...

A Common Garter Snake (Thamnophis sirtalis) on the left and a Pacific Chorus Frog (Pseudacris regilla).

And finally, as the title of this blog suggests, I did turn up one flying odonate: a teneral (recently emerged) male Pacific Forktail (Ischnura cervula) which flew up from some emergent sedges as I was wading into the water...

A teneral (recently emerged) male Pacific Forktail (Ischnura cervula) in Vancouver, Washington, on
8 April 2011.

Over the next few days, those dull grayish areas on the thorax and abdomen will turn blue (like those small spots above the eyes) and the eyes will turn black and green. Compare this individual with a mature male in a recent post.

So that was a couple hours today in a nearby wetland. It always feels good when I find my first adult odonate of the season. Somehow it just feels like everything’s going to be okay.

Postscript, 8 April 2011

Mike Patterson at North Coast Diaries pointed out that the robber flies photographed here are probably dance flies. Browsing through BugGuide.net, I had to agree, and there are several photos of Empis in Empididae that look like a good match. Males actually present a nuptial gift of prey before copulating and that must be what the female of the copulating pair is holding. Before I had a chance to add this postscript, Steve Collins confirmed that these are dance flies and also suggests the genus Empis. Thanks to both Mike and Steve!

The Pacific Northwest's First Fliers

2011-03-31T22:07:00.000-07:00

Usually around mid-February my mind becomes occupied with thoughts of when the weather will turn sunny and warm enough to bring out flying odonates in my area (Vancouver, Washington). My general rule-of-thumb conditions for the first flying odonates of the spring are about three consecutive days of around 60° F or more and at least partially sunny skies. Of course, a few odonates could be flying before those conditions are met, but it’s what I look for before I start thinking, “There must be something flying now.”

This year, unfortunately, the spring weather has been unusually cool and wet—just across the Columbia River from me, Portland, Oregon has broken its latest first 60° (F) day record (which still has not been attained as of this writing) and its number of March days with measurable rainfall record (currently 28 days). This has been a tough spring for me.

Even though odonates are late this spring, let’s be prepared for those first few warmer, sunnier days which must come eventually. I promise they will. They have to, right? What should you look for? Below are photos of some of the earliest fliers in the western Oregon/Washington region, roughly in the order that I expect to see them. Exceptions certainly occur, and the line up may vary depending on where you are and the types of places you visit. There are a couple of other contenders for this group of first fliers, but I went with the five species that I think of as most likely.

Pacific Forktail (Ischnura cervula): In my last post, I shared a photo of a male of this very common and widespread species. Females are quite variable depending on their maturity and whether they are gynochromatic or androchromatic—“female-colored” or “male-colored”, respectively. Below is an immature gynochromatic female with its extensive pinkish coloration on the head and thorax and single blue segment near the end of the abdomen.

Swift Forktail (Ischnura erratica): This is the biggest member of the genus in the Northwest with bold blue and black stripes on the thorax and typically some extra blue near the end of the abdomen. Look for it at ponds in forested areas west of the Cascades.

Variegated Meadowhawk (Sympetrum corruptum): This is the migratory species occasionally seen in large numbers at coastal locations during August and September when the conditions are right. Presumably, the earliest spring adults are migrants from the south. Mature individuals look dusty orange from a a distance, but up close you will see an intricate pattern of dull reds, browns, yellow, and white.

Cardinal Meadowhawk (Sympetrum illotum): Another meadowhawk, but unlike the previous species, mature males are about as red as red gets. They simply glow and are very distinctive. (Working these images on my laptop, I’m not sure that I have the saturation right, but you get the idea.) They even have an amber wash over the basal portions of the wings.

Tule Bluet (Enallagma carunculatum): Like the Pacific Forktail, this species is very common and widespread, and can be seen at just about any fresh water wetland that has at least some emergent vegetation. There are several species of Bluet in the Northwest and they all superficially look like this, but this is the ubiquitous species of lower elevations west of the Cascades.

Have you seen any odonates yet this spring?

Just a Photo: Pacific Forktail (Ischnura cervula)

2011-03-26T22:00:00.000-07:00

A male Pacific Forktail (Ischnura cervula) in Albany, Oregon. This very common and widespread species is
one of the first to start flying in the Pacific Northwest. This spring has been uncharacteristically cool and
wet, but they should be out any time now as soon as we get a few warmer, sunnier days (at least where
I am in southwest Washington—it could be a few more weeks further north).

Somebody Lost Her Head

2011-03-16T20:45:00.000-07:00

A few weeks ago an odonatist friend made a general request of photographers to look through their photos and see how frequently adult dragonflies other than libellulids (skimmers) are hosts for water mites. When you spend a lot of time looking at odonates, it becomes clear that certain groups (like several libellulid genera and a variety of damselfly genera) are frequent water mite hosts, while other dragonflies in non-libellulid families and some libellulid genera rarely host water mites even if they breed in aquatic habitat that is suitable for mites. The subject of water mites is an interesting one and I’ll write more about them another time, but all of this leads me to the real subject of this post...

So, I was scanning through my dragonfly photo collection looking for water mite carriers, when I came across a male Diminutive Clubtail (Gomphus diminutus) that I photographed in South Carolina a few years ago. I noticed that it had a reddish-brown, bulbous thing on one of its front legs which looked superficially like a water mite except that it was too big and legs are a strange place for a water mite to make its temporary home (typically they attach to the lower areas of the thorax and abdomen). I decided that it wasn’t a mite, but I couldn’t really tell what it was.


A male Diminutive Clubtail (Gomphus diminutus) in Chesterfield County, South Carolina, 9 May 2008. See the reddish-brown thing on one of the front legs under the head?

Digitally zooming in on the dragonfly’s front leg, the UFO (unidentified femoral object) began to take on a recognizable shape, but I wanted to be sure. I indicated that I collected this individual in the photo’s metadata and I’m glad I did that. Since I started odonate photography in a serious way, I’ve been cross-referencing photos to collected specimens and vice versa which can be really handy for a variety of reasons. One reason is that I have the specimen to verify the identity of the photographed odonate (important for more cryptic, difficult-to-identify species); another is that I can verify the body and eye colors of a specimen in life (eye color does not preserve at all in specimens and body color can fade or darken significantly).

I pulled the specimen out, put it under the microscope, and the UFO was what I thought it was—the head of an ant gripping the clubtail’s leg with its mandibles. Like many gomphids, the Diminutive Clubtail frequently perches on the ground and I presume that the ant came along and took on the dragonfly as potential prey, as misguided as that may be. The location on the front femur where the ant head held tight is within reach of the clubtail’s mandibles, so I’m sure that the dragonfly simply bit down on the ant’s body and yanked. The ant was resistant, of course.

A close-up of the photo above. Yeah, that’s an ant’s head.

Ants are a major threat to emerging odonates—they can’t fly or run and the exoskeleton is very soft and vulnerable to pinching mandibles. Emerging odonates don’t stand a chance when they are discovered by ants, but mature odonates simply fly off when their personal space is invaded. This ant must have grabbed on before the clubtail could take off, but it was a lethal mistake.

I find it easy to anthropomorphize odonates and I imagine this clubtail showing off the “trophy” on his upper arm as the victor of an epic battle. I’m sure the clubtail didn’t intentionally leave the ant’s head on his femur, but anthropomorphizing is fun sometimes.

I Heart Damselflies

2011-02-14T07:57:00.000-08:00

Are copulating damselflies the source of the stylized heart shape (❤) that we’re all familiar with and drew on Valentine’s Day cards in grade school? Let’s see what we can do with this image of copulating Skimming Bluets (Enallagma geminatum) and you be the judge...

Well, what more proof do you need! This isn’t my idea. I recall someone speculating about it years ago (sorry, I don’t remember who that was) and a sketch depicting this notion was used on a cover of Argia, the news journal of the Dragonfly Society of the Americas, back in 1997. You can view that issue here.

Copulating damselflies don’t always form such a nice heart shape—it’s often skewed like on the cover of that issue of Argia, but there is usually at least a suggestion of it. Copulating dragonflies never form a heart—not that I’ve seen anyway, and that probably has to do with the difference in where the male holds onto the female (the back of the head on dragonflies, near the front of the thorax on damselflies), and differences in body proportions may have something to do with it too.

I don’t known if copulating damselflies are truly the source of the heart shape or not and I’m sure that no one knows for certain anymore, but it’s fun to think about. And of course, Valentine’s Day is a natural time to think about it. (Wikipedia has a few suggestions about the origin of the heart shape, none of which involve damselflies.)

I have a suggestion. From now on whenever you see a “I ❤ something” sticker, mentally replace the heart with “copulating damselflies”. I copulating damselflies NY or I copulating damselflies my rat terrier is so much more entertaining!

The Rubyspot Up Close and Personal

2011-02-11T15:57:00.000-08:00

This is one of my favorite photos: A female American Rubyspot (Hetaerina americana) in the Umpqua Valley of Oregon. She was very cooperative, perching on very light river cobbles with more light cobbles in the background. This really allows us to get a look at the fine patterning and color transitions.

Female American Rubyspot (Hetaerina americana) on the South Fork Umpqua River, Oregon.

I just love looking it over and soaking up all the little details—the coppery/bronzy sheen on the dark brown parts of the body, the pattern of light and dark on the thorax and abdomen, the white wing veins against the dark reddish-brown wing base, how those reddish-brown bases transition to amber and then almost clear where the veins are dark, the one major vein that is white out to the wing tip with a fuzzy red stripe paralleling it.

Here are some crops that show off particular areas better:

In this close-up, note the red veins on the fore wing (partially hidden by the hind wing).


She has an indistinct pterostigma (the darkened cell near the tip along the leading edge). In some populations it is very pale and obvious, while in others it is indistinct or lacking.

This species is widespread across the eastern and southern US (barely into Canada), but largely avoids the Pacific Northwest where it is known only from Oregon in the Umpqua and southern Willamette Valleys as well as the Klamath River. Here’s a map of the entire range at OdonataCentral.org.

Zenithoptera: The Morpho of the Dragonflies

2011-02-04T19:05:00.000-08:00

I’ve always intended to keep a primarily Pacific Northwest (of North America) focus to this blog, or at least stick to topics relevant to odonates in this region, but this is one of those times that I’ll deviate from that scope. There are just so many cool odonates in other parts of the world worth sharing, and the subject of this post is in the northwestern part of South America, so I call it good.

One of my most memorable encounters with dragonflies was the first and only time I saw a member of the genus Zenithoptera. I was in the Amazonian lowlands of Ecuador with a couple of friends walking into a sunny clearing with a low, boggy area. Around a small pool of water were these little dragonflies with stunning velvety blue upper wing surfaces. One of my companions had found this spot on a previous trip and wanted to share. The other trip mate told us later that he thought those little blue gems were butterflies and, while admitting that they were very beautiful, wondered why we were so intent on photographing them. He was shocked when he got a good look and realized that they were, in fact, odonates.

There are four recognized species of Zenithoptera which range over much of northern South America—one getting as far north as Costa Rica. The one species that I’ve seen (and the one pictured throughout this post) is Z. lanei and, besides Ecuador, is recorded from Peru, Brazil, Venezuela, Paraguay, and Argentina.

Zenithoptera lanei. Top to bottom: male side view;
male front view (looks like a flower to me); male
with wings raised; pair copulating.

If you focused only on the body of Zenithoptera—the head, thorax, and abdomen, you’d think these were among the dullest, least interesting odonates that you’ve ever seen. Ah, but the wings are what make them so stunning with that kind-of-hard-to-describe silvery, slightly iridescent blue over the upper surface with just a hint of pale patterning. The color on the females’ wings is a vivid, almost metallic, deep blue with more obvious pale patterning. The underside of the wings is very dark—almost black, and that vague pale pattern on the upper surface shows very clearly on the underside. The wings are reminiscent of the blue species of Morpho butterflies, although Zenithoptera lanei are much smaller—only about an inch long with a wingspan of about two inches.

But, wait, there’s more! The wing coloration isn’t even the coolest feature of Zenithoptera. I mentioned in another recent post that you’ll find exceptions to almost every “rule” as you delve into the world of odonates, and this is one of those cases. One of the basic differences between dragonflies and damselflies is that dragonflies perch with the wings open and out to the sides while damselflies typically perch with their wings closed over the abdomen. There are actually a lot of exceptions to that rule among the damselflies, especially in the tropics, but, at least in the New World, only the Zenithoptera among the dragonflies ever perch with the wings closed—straight up over the thorax. This is what puts the “Zenith” in Zenithoptera. It’s really a very odd thing to behold the first time you see it.

Zenithoptera don’t always perch with the wings closed. During my brief experience with them in Ecuador they spent most of their perching time with the wings fully open (and actually drooping quite a bit like some dragonflies do, looking like flowers when viewed head-on) exposing that beautiful blue color, and only closed them occasionally for short periods. I don’t think anyone really knows why they do it. If the wings were kept closed most of the time I’d suspect it was to avoid being spotted by predators (particularly birds), but the ones I observed kept their wings open a majority of the time. To me it almost seemed to be a signal among the Zenithoptera, but what exactly was being signaled, if that’s what it was, is beyond me. Even pairs that were copulating alternated between open and closed wings. When the male closed his wings, the female’s head would be hidden. I wonder what she thought about that.

There is more Zenithoptera weirdness—are you sitting down? This next trick really blew my mind. I was photographing a female perching alongside the pool when she raised only the hind wings to the folded vertical position, but left the fore wings in the open position. After a couple of seconds the hind wings were dropped for a while just like the fore wings, then she did it again. She repeated this several times while we watched her, periodically raising only the hind wings for two or three seconds each time, and luckily I kept my head well enough to photograph each state.

Female Zenithoptera lanei. All wings in the open position on the left; only the hind wings raised in
the closed position on the right. What do you think she is doing?

The wing-raising behavior of Zenithoptera is well-known, but I had never heard of one raising only the hind wings. The periodic, seemingly methodical movements really seemed to be some sort of signal, but there’s no way to be sure of that. I think we had just seen this particular female copulating a minute or two earlier, so perhaps she is telling other males in the vicinity that she won’t be interested for a while. This is only speculation on my part, however. I would love to hear comments on this behavior (both the raising of all wings and the raising of only the hnd wings) if you have any ideas about it.

If I was to pick one odonate as my favorite (as I did in a recent comment on The Dragonfly Woman’s blog), I would have to go with the beautiful, stunning, unusual Zenithoptera. I hope it isn’t too long before I see them again!

Postscript

As Dennis Paulson points out in his comment, “zenith” in this case likely refers to the sky blue color of the wings, not the aiming of the wings toward the zenith of the sky. This makes sense considering that the describer, Selys, would not have seen these dragonflies in life. Thanks go to Dennis for setting me straight, but I think the behavior is very fitting of the name.

Returning to the Depths: Submerged Oviposition

2011-01-24T18:48:00.000-08:00

I suspect a lot of people don’t realize that some odonates deposit their eggs while submerged. I don’t mean that they simply stick the end of their abdomen below the water surface to lay their eggs (which is also done), but sometimes they completely submerge themselves.


An ovipositing River Jewelwing (Calopteryx aequabilis) on the South Fork of the John Day River, Oregon. Only the distal two-thirds of the wings are above the water surface.

The behavior is almost completely restricted to damselflies (suborder Zygoptera) which all oviposit endophytically—inserting their eggs into plant material instead of just dropping them from the end of the abdomen. It is rare among the dragonflies (suborder Anisoptera), probably because it’s difficult for them to break the surface tension with their broad wings sticking out to the sides. Damselflies must be better able to pierce the water’s surface with their wings folded together over the abdomen.

This behavior seems counterintuitive for a group of insects with relatively long, narrow wings unprotected by a rigid covering while at rest (as is the case with beetles and true bugs), but some species oviposit in this way frequently or even exclusively (for example certain bluets [Enallagma], jewelwings [Calopteryx], and rubyspots [Hetaerina]). It is infrequent in some other genera, but it could be more common than is realized. I’ve only observed it a few times, although it isn’t very conspicuous—damselflies crawling down a plant stem to get under the surface don’t exactly draw your attention, and once submerged they are pretty difficult to spot.

A completely submerged Appalachian Jewelwing
(Calopteryx angustipennis) ovipositing in
Wilson Creek, North Carolina.

Philip Corbet, in his monumental Dragonflies: Behavior and Ecology of Odonata (1999), summarized what was known about underwater oviposition up to that time. According to him the duration of uninterrupted submerged oviposition is often at least 30 minutes and frequently close to an hour. Apparently the record goes to the Marsh Bluet (Enallagma ebrium) which is known to go submerged for an incredible five hours! Descending to at least 10 centimeters is common, but some are known to go as far as a meter below the surface.

Considering that odonates abandon their water-breathing gills when they emerge, how do the adults get their oxygen when they return to the depths? A thin envelope of air clings to the body and wings which gives them a silvery appearance while they’re under water. Body movements likely force the air in and out of tracheal openings facilitating respiration.

There are of course pros and cons associated with submerged oviposition. Potential advantages are that the female (or pair, if that’s the case) is free from harassment by males looking to copulate, and the risk of desiccation to the eggs is reduced in habitat where the water level can fall substantially during the flying season—the lower she goes, the longer the eggs will stay wet. There is a risk of drowning for the female when she is unable to break free of the surface tension—possibly because immersion in cool water for a time saps her strength, but she could also be rescued by a male who goes into tandem with her with the intent of copulating. The eager mate might provide enough lifting force to break her free of the surface, or else he could “tow” her across the surface to something like a plant stem where she can climb out (imagine an ultralight aircraft towing a water skier).

A pair of Northern Spreadwings (Lestes disjunctus) ovipositing in tandem at Frater Lake, Washington.
They are several inches below the surface (note the meniscus near the top right corner). Spreadwings
typically perch with the wings spread open—including when ovipositing, but note that both are
keeping their wings tightly closed in this case.

Considering that odonates spend most of their life in water (as nymphs), it doesn’t seem all that unnatural for them to return to the depths to complete their life cycle and produce the next generation. Watch for this inconspicuous behavior. It probably happens more frequently than we know—and right under our noses (well, right under the water).

Insect Alchemy: The Maturing Female Western Forktail (Ischnura perparva)

2011-01-14T19:00:00.000-08:00

Female damselflies of the genus Ischnura, the Forktails, often go through a pretty dramatic color change during their time as an adult. In many species they start out wearing some pattern of black-and-orange, and as they mature the orange areas dull to some less interesting hue like muddy yellow, and they may simply darken altogether. During this transition in color, females of some species start developing a coat of pale gray pruinescence—a fine, waxy, powdery film, which eventually covers much of the exoskeleton.

The Western Forktail (Ischnura perparva), abundant and widespread in the Pacific Northwest and much of western North America, is one of those species that performs this insect alchemy, changing from gold to silver. The orange stage is typically referred to as “immature”, but orange and pruinescent females are both seen copulating with males so they aren’t necessarily reproductively immature. If you didn’t know any better you might think each was a different species. Here’s a series illustrating the transition...

A classic immature female with orange areas on the head, thorax, legs, and abdomen.


This is intermediate with the orange areas on the thorax turned to dull grayish-yellow, the black shoulder stripes broader, and the abdomen almost all black now. A very thin coating of pruinescence is starting to show. Note the change in eye color.

Further along with lots of pruinescence—especially on the abdomen, but the thoracic stripes
are still clearly visible.

Fully mature with the thoracic stripes almost completely obscured.

Note how the eye color changes to vivid green with a sharply defined black “cap” and that the lower sides of the thorax turn pale green. The transition to the fully mature pruinescent stage seems to occur relatively rapidly since intermediates like the second individual are not often seen.

So here’s an exception (as I delved into the world of odonates I learned pretty quickly that there are exceptions to almost everything, and even some exceptions have exceptions—it get’s complicated): a very small number of female Western Forktails are androchromatic (or male-colored) and the pale areas on the upper part of the thorax are green instead of orange and there are blue rings near the tip of the abdomen. To continue the alchemy analogy, I guess this would be turning copper and cobalt into silver. I've only seen one example of an androchromatic Western Forktail which is pictured below.

An androchromatic immature female with a light coating of pruinescence. The dark red spots behind
the head are water mites—I’ll talk about those in a future post.

This variant is pretty rare, although it may not be quite as scarce as we think since they end up covered with pruinescence just like the typical gynochromatic (or female-colored) females, and by then they all look alike. It’s a matter of timing. Keep your eyes open for them.

Black Petaltail (Tanypteryx hageni), the Dragonfly of Soggy, Seepy, Slopes

2011-01-07T18:21:00.000-08:00

One of my favorite odonates is the Black Petaltail, Tanypteryx hageni, and I presume it makes the top five on most Northwest odonatists’ lists for a number of reasons. It’s always a joy when I can see and handle these creatures, but especially so when I stumble across them unexpectedly during an outing.

This species’ family, Petaluridae, is a small one with only eleven species, nearly all of which are distributed around the Pacific Rim. Seven of these are found in Australia and New Zealand which seems unfair, and some of those are among the largest odonates in the world. The Petaluridae are known as petaltails because the males of most species have relatively broad, flat cerci (upper abdominal appendages) which are reminiscent of flower petals.

Male Black Petaltail (Tanypteryx hageni)
at Eight Dollar Mountain, Oregon.

The Black Petaltail is the sole western North American representative of the family, distributed from northern California (and barely into Nevada) to coastal mainland British Columbia (but strangely not on Vancouver Island) as this map at OdonataCentral.org illustrates. The only other member of the genus is Tanypteryx pryeri of Japan. The more distant cousin Gray Petaltail, Tachopteryx thoreyi, occupies woodlands in a large swath of the eastern US from east Texas to New Hampshire.

Adult Black Petaltails are largely black, as the name suggests, with a complex pattern of yellow spots on the thorax and abdomen, a mostly yellow face, and dark chocolate brown eyes—and if you get a close look note that there is a gap between the eyes on top of the head (only the clubtails, Gomphidae, share this characteristic among the dragonflies). It’s a relatively large species among the Pacific Northwest odonates, although it is near the small end of the spectrum among the Petaluridae and it doesn’t quite reach the size of most of our darners (Aeshnidae). They are fairly approachable as dragonflies go and it’s not unusual for them to perch on people—especially those wearing very light-colored clothing, and this imparts upon them a warm and fuzzy “personality”.

Look for Black Petaltails in forested areas with open or partially open seepy slopes with a soggy substrate of mud, moss, and herbaceous plants, fed by springs or small streams. In Oregon and Washington these sites are mostly in the Cascade and Olympic Mountains above about 2000 feet elevation, but they also use Darlingtonia (a pitcher plant) fens in southwest Oregon, some of which are as low as 1000 feet elevation. There was once a population on Mary’s Peak—the highest point in the Oregon Coast Range, but they have not been seen there in decades and I’m not sure anyone alive knows where the site was anymore. In 2009 Mike Patterson found a population on Onion Peak, Clatsop County, which is currently the only known Oregon Coast Range population. There must be others.

A Black Petaltail (Tanypteryx hageni) nymph at its
burrow entrance after dark. Photo by Cary Kerst.

Being aquatic insects, the nymphs of the Black Petaltail live in the saturated substrate on those soggy slopes. And they don’t just crawl around in the muck—they actually construct burrows into the mud and organic matter and this is what makes the species really unique among the North American odonate fauna (and this is true of most members of the family). The nymphs are partially terrestrial after dark, sitting at their burrow entrance where the ground is wet, but above standing water (see Cary Kerst’s photo at right). Here they wait for prey to amble by, but they may also wander a bit to hunt.

The burrow entrance of a full grown nymph is about a half inch or a little more in diameter and there is often a small pile of excavated mud just off the threshold if it’s in use. They can be really difficult to spot, but it gets easier after you've seen a few. During the day you can sometimes see the occupant hanging back in the shadows of their burrow, and at times you can even fish them out with a blade of grass. If you do fish one out, be sure to return it to its home if you don’t intend to collect it. The nymphs take five years or so to get to full size—maybe a bit more at the highest sites, maybe a bit less at the lowest Darlingtonia sites. Of course once they emerge and become adults, they don’t live beyond the season.

Adult females lay eggs by inserting the end of their abdomen into the muck and mosses while grasping vegetation or clinging to the side of a log. They are difficult to see while they’re ovipositing, especially when surrounded by taller plants, but you often hear their wings vibrate or rattle against vegetation periodically and that can help you zero in on their location. Adults are often found soaking up the rays on logs, boulders, and tree trunks, and they don’t appear to wander very far from nymph habitat—at least not as much as other dragonflies. If you happen to come across one in the hills, there is probably a soggy slope in the area.

Female Black Petaltail (Tanypteryx hageni) at Todd Lake, Oregon.

A female Black Petaltail (Tanypteryx hageni) ovipositing in a Darlingtonia fen at Eight Dollar Mountain, Oregon.

So keep an eye out for the Black Petaltail when you’re in the hills on warm sunny summer days. It’s a special dragonfly in my opinion. And if you find some soggy slopes, look for the little burrows of the nymph and go fishing!

Happy 2011!

2010-12-31T17:40:00.001-08:00

Happy New Year from the frigid Methow Valley in north-central Washington where there isn't a single odonate to be seen (and I'm not going to look for nymphs in the icy depths)!

Here's to a great 2011 filled with dragonflies!

Is that a Dragonfly or an Odonate?

2010-12-28T18:30:00.000-08:00

I frequently use the term “odonate”; sometimes it’s “dragonfly”; sometimes “damselfly”. Probably not everyone understands the distinction between these labels, so I hope this post will clear things up. Let’s look at these terms and others just to make sure we’re all on the same page:

Odonata: This is the taxonomic order which encompasses dragonflies and damselflies. It essentially means “toothed ones” referring to their strong, sharp mandibles. This term can be modified to “odonatology” (the study of Odonata) and “odonatologist” (one who studies Odonata).

Odonate: A general term for any insect in the order Odonata. I try to use this term when I speak of dragonflies and damselflies collectively or when I’m talking about particular species ambiguously. An “odonatist” is one who has an interest in odonates.

A male Eight-spotted Skimmer (Libellula forensis).
This is an odonate and a dragonfly.

Dragonfly: This term can be confusing since it may be used in a strict sense or a loose sense. In the strict sense it refers specifically to those odonates in the suborder Anisoptera—these are the classic dragonflies (like the Skimmer at right) and it excludes damselflies. You could also say “anisopteran”, but that’s pretty techy for laypeople. In the loose sense “dragonfly” is synonymous with “odonate”, so inclusive of damselflies.

I try to avoid using this term in the loose sense, but sometimes it’s just quicker than saying “dragonflies and damselflies” when I’m amongst company who may not understand “odonates”. When browsing book titles on “dragonflies” keep in mind that it may or may not include damselflies. The name of this blog, Northwest Dragonflier, is in the loose sense since Northwest Odonater or Northwest Odonatist

A male Tule Bluet (Enallagma carunculatum).
This is an odonate and a damselfly. Sometimes
it’s a dragonfly depending on the speaker/writer.

wouldn’t mean anything to many potential readers, and Northwest Dragonflier and Damselflier is just unwieldy in my opinion.

Damselfly: This one is much simpler since it only refers to odonates in the suborder Zygoptera (the damselflies, like the Bluet at right) and never includes dragonflies (in the strict sense). Just as you can with the other suborder, you can get technical and say “zygopteran” if you want to put a puzzled look on the faces of your uninitiated friends which is always fun.

So the title of this post is a bit of a joke since dragonflies are odonates and odonates are dragonflies—in the loose sense, anyway.

Damselflies Have a Good Head on Their Shoulders

2010-12-22T14:40:00.000-08:00

One way damselflies differ from dragonflies is in the head shape. From above a damselfly's head is relatively short (from front to back) and wide with the eyes capping the ends—what could be described as “hammer-headed”. Unlike dragonflies, there is always a gap between the eyes which is at least the width of one of the eyes—usually more. See the image at right which illustrates the distinctive head shape.

Does this hammer-headed condition give damselflies some sort of advantage? I think it does. Damselflies frequently perch on long, skinny, near-vertical things like grass stems, sedges, and twigs, with the head facing whatever they’re grasping and the abdomen pointing away. The widely separated eyes provide them an unobstructed view around narrow perches, which means they can keep an eye out—well, both eyes out—for whatever they need to look out for. I would guess a narrow perch does not block the damselfly's view at all even though it's right in front of the face.

The photos below illustrate this point. This California Spreadwing (Archilestes californica) was perching on a sedge at the Cottonwood Recreation Area on the John Day River in Oregon. After a few profile photos, he stayed put while I angled around for the front shot. Very cooperative!


Two views of a male California Spreadwing (Archilestes californica) perching on a sedge stem.

What do they need to look out for? Predators are an obvious choice, although I’m not sure how noticeable damselflies are to predators while perching. It must happen sometimes, though. They do often perch-hunt however, waiting for prey to fly within striking range and then taking their lunch back to a perch to finish up. Mature males are also always on the lookout for females, so whatever enhances their view is good for that too.

Do Dragonflies Bite or Sting?

2010-12-14T21:32:00.000-08:00

I am regularly asked at talks and workshops whether dragonflies bite or sting. The question is posed frequently enough that it is included on a Frequently Asked Questions slide, and I figure that enough people wonder about it to warrant a blog post. This concern doesn’t seem to apply to damselflies necessarily, probably because most of them are small and seem less threatening, but in this post I’m referring to all of them—odonates.

My quick (Tweet-sized) response to this concern over biting and stinging is that odonates do neither to people. If you’re content with the abridged response, you can stop reading, stop worrying about dragonflies inflicting pain, and you’ll be fine. The whole story is a bit more complicated and, I think, more interesting. If you’re curious, continue reading…

Now, it is true that all odonates are predators and that they have formidable, shredding mandibles which make quick work of their meals. If you’ve never looked at the mandibles of a largish species with a hand lens or microscope, you should—they are impressive. It is also true that when you handle an odonate, they frequently reveal their mandibles (by flexing the labrum and labium) and repeatedly open and close them. This is no doubt a reflexive response to being in the grasp of a “predator”.

If those mandibles happen to come into contact with the handler’s skin (particularly the softer webbing between the thumb and index finger), they will close. It is usually more startling than anything else when it happens, but the larger species can inflict a painful pinch and even break the skin sometimes. They will all try it, but the small species (especially the smaller damselflies) have mandibles which are too small to grab the skin and their nibbling feels a little ticklish at worst. When someone receives a painful bite, it is their own fault because they handled a dragonfly in such a way that mandible-to-skin contact was possible.


An ovipositing female Paddle-tailed Darner (Aeshna palmata). The arrow points at the "stinger".

What about stinging? The females of some odonates are equipped with what could be described as a “stinger”, but this is used strictly for laying eggs—never as a weapon. These are sharp, sickle-shaped blades (known as gonapophyses in geek-speak) which are used to incise an opening in plant material where an egg is inserted. All odonates which lay their eggs endophytically (within plants) have this equipment. This means all of the damselflies and, among North American dragonflies, only the darners and petaltails.

Technically a person can be “stung” by a dragonfly, but it is very rare, and is never committed with the intent of causing pain. This happens when someone’s leg is mistaken for a log or tree stump by a female darner who is just looking for a place to lay eggs. I’ve only heard of it happening a few times, but I would guess that stories of huge stinging dragonflies are more frequent among anglers who often sit along the shores of lakes and streams with bare legs. I have also heard that it is rather painful which doesn’t surprise me.

I have never heard of anyone being “stung” by a damselfly. I presume it is possible, but I think most of them are too small to pierce the skin. The large spreadwings (Archilestes) have hefty ovipositors good for inserting eggs into woody willow and alder branches, and I imagine that they would be up to the task if so inclined.

Several years ago a female darner landed on my jeans just below the knee and started to lay eggs in the fabric. She seemed oblivious to my head and arm movements until I shooed her away—it was interesting and fun to watch, but I didn’t want her to waste her eggs on my denim. I wonder if I would have been a stinging victim if I had been wearing shorts instead, but I like to think that all the hair would have clued her in.

So, that’s the whole story on biting and stinging odonates. The thing to remember is that a free-flying dragonfly will never bite you. Even if it lands on you, it will not bite. Though stinging, technically, can happen, it is extremely rare and it is never done as a defensive or malicious act. Even if you swat at a dragonfly that is too close for comfort (why anyone would do that, I don’t know), it will never bite or sting as a defensive measure as yellow jackets and honey bees might when they are agitated. Odonates will simply fly away.

Why now?

2010-12-07T18:00:00.000-08:00

It isn’t technically winter yet, but I haven’t seen a dragonfly or damselfly in the Pacific Northwest since the 5th of November (just over a month ago), which is a good enough reason for me to conclude that it is winter around here. It may seem like an odd time of year to start a blog about these insects—when you can’t just go outside and reasonably expect to see one, but it actually seems like a pretty good time to me.

I’m not busy right now looking for and photographing dragonflies and damselflies; I don’t have a backlog of specimens and photos to process and catalog; I’m not making updates to my web site at the moment. I guess I have a little more time to do it right now. Maybe writing an occasional blog post through the winter months will keep others interested until the warmer, sunnier days of spring when they might be able to go outside see some live examples (assuming the weather cooperates). Maybe it will keep my cerebral “dragonfly muscle” exercised through these dark days. Maybe it will just be fun.

Posts on this blog will be all about odonates—dragonflies and damselflies. Topics will range from the very general, which apply to the group as a whole, to particular species. When I write about particular species they will primarily be ones that occur in Oregon and Washington, but I will branch out on occasion and write about more exotic species when the mood strikes me. At any rate, welcome to my inaugural blog post and I hope you’ll be a regular reader.

Until my next post, here's some bright and cheery eye candy:

Symptrum pallipes (Striped Meadowhawk), Sprague River, Oregon, 25 July 2010.