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:



  • 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)?

4 comments:

  1. Very nice post (and blog, which is new to me), but I feel obliged to admit I've mistaken another insect for a dragonfly. Nut only once, and from a distance!

    The first time I saw a robber fly it was perched over a stream in a very odonate post, and with that long body and big eyes, and me too far away to make out the wings... well I thought it could have been a dragon.

    The species isn't all that dragonfly-like up close, so I'm not sure you can move the asilids on over to the dragonfly-like.

    The only really dragon-fly like insects I can think of are owlflies (sister to antlions I think) which do reas with wings out-stretched.

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  2. @david winter Hi David, yes I can see how those big robber flies could be mistaken for a dragonfly from a distance.

    That's a good point about owlflies too. Those aren't in my neck of the woods, and I think I've only seen them in Ecuador, so it didn't occur to me. Their antennae are crazy long, so that would be a good clue that they aren't an odonate.

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  3. My two-year-old grandson has an older book called "My First Animal book" which has a Damselfly mis-labeled as a Dragonfly. Somebody did not proofread very well!

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  4. Yonassan, in Europe they call all Odonata dragonflies, not making the distinction between the two suborders in common names.

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