Saturday, November 19, 2011

The Spotted Spreadwing (Lestes congener): A Quick Look

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).

Thursday, November 10, 2011

Another late visit to Ice House Lake

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.

Monday, October 31, 2011

Halloween Fun

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

Friday, October 28, 2011

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

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.

Sunday, October 23, 2011

Recent Outings on the Lower Columbia

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.

Saturday, October 15, 2011

Fun With Darners!

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.

Friday, October 14, 2011

Just a Photo: A Table for One

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.

Friday, September 30, 2011

Just a Photo: Chaotic Cluster

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.

Tuesday, September 27, 2011

ID Challenge #3 Answer

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).

Thursday, September 22, 2011

ID Challenge #3

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.

Monday, September 19, 2011

Some Non-Odonate Critters

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.

Thursday, September 15, 2011

Obelisking: Sticking it Where the Sun Shines

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.

Wednesday, August 24, 2011

Don’t Fear the Dragonfly

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.

Wednesday, August 17, 2011

It's Time to Watch for Migrant Meadowhawks

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. 

Thursday, August 11, 2011

Now THIS is Recycling: Jumping Spiders Using Dragonfly Exuviae

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?

Monday, August 8, 2011

Lake of the Woods, Oregon

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.

Tuesday, August 2, 2011

Snaketail Emergence Sequence

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.

Monday, July 18, 2011

Just a Photo: Spiketail Nymph

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.

Friday, July 15, 2011

ID Challenge #2 Answer

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.

Friday, July 1, 2011

ID Challenge #2

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.

Friday, June 24, 2011

A Great Day for Emergence at Camas Prairie

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

Wednesday, June 22, 2011

Alvord Basin Weekend, 17–19 June 2011

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.

Sunday, June 12, 2011

John Day River Outing, 11 June 2011

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.

Thursday, June 9, 2011

Just a Photo: A Table for Eight, Please?

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).

Monday, June 6, 2011

A Few Ecuadorian Odonates

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 . . .

Monday, May 9, 2011

Identification: Dragonflies versus Damselflies

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.

Wednesday, May 4, 2011

A Dragonfly Emergence Sequence

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.

Sunday, April 24, 2011

Just a Photo: What I dug up the other day

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.

Friday, April 22, 2011

A One Species Day, 22 April 2011

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.

Tuesday, April 19, 2011

ID Challenge #1 Answer

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.

Friday, April 15, 2011

ID Challenge #1

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.

Monday, April 11, 2011

Things that are NOT Damselflies

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:

Friday, April 8, 2011

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

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.

Thursday, March 31, 2011

The Pacific Northwest's First Fliers

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.

Saturday, March 26, 2011

Just a Photo: Pacific Forktail (Ischnura cervula)

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).

Wednesday, March 16, 2011

Somebody Lost Her Head

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.

Monday, February 14, 2011

I Heart Damselflies

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...

Friday, February 11, 2011

The Rubyspot Up Close and Personal

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.

Friday, February 4, 2011

Zenithoptera: The Morpho of the Dragonflies

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.

Monday, January 24, 2011

Returning to the Depths: Submerged Oviposition

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.

Friday, January 14, 2011

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

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.

Friday, January 7, 2011

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

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 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!