ID Challenge #4 Answer

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Ready for the solution to ID Challenge #4? Let’s start at the top as we consider this mystery Pacific Northwest odonate: Is it a dragonfly (Anisoptera) or a damselfly (Zygoptera)? Probably most people can take a glance and immediately recognize it as a dragonfly, but how do we know for sure?

It looks pretty bulky, the “face” looks relatively flat rather than “snouted”, and the head does not seem very elongated from side-to-side (hammer-headed or dumbbell-shaped with the eyes capping each end). These are all indicators of dragonflies, but another more concrete character is the width of the gap between the eyes at the top of the head. On damselflies that gap is greater than the diameter of either eye; on dragonflies, if a gap is present, it is less than the diameter of either eye. Even at this angle we can see that the gap is smaller. Definitely a dragonfly. You can also just make out that the margin of each eye is angular at the narrow point of the gap—something else you won’t see on a damselfly. Here’s a post I did a while back on differentiating dragonflies and damselflies which illustrates the head/eye shape.

ID Challenge #4

Wow, it’s been a long time since we’ve had an ID Challenge! Here’s a close-up of some mystery odonate which is found in the Pacific Northwest (or parts there of). Where else does it occur? I’m not saying. If you’re familiar with the species, it ought to be pretty easy. If you’re not familiar with it, it’ll take a bit of research.

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

Have fun!


Postscript, 6 December 2012

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

Season's Feastings, the Odonate Way

It’s Thanksgiving time in the US, and I’ve been wondering how I could possibly tie a post about dragonflies and damselflies to the holiday. It’s far too chilly and sunless around here to show any odonates enjoying the season. The best I could come up with was a bunch of photos of dragonflies and damselflies eating to their hearts’ content. That is, after all, how many Thanksgiving celebrants observe the day.

High Speed Video of Flying Dragonflies

I recently became reacquainted with this interesting National Science Foundation video on YouTube, and I thought it was worth sharing. Titled Science Nation - Dragonflies: The Flying Aces of the Insect World, it features a species of the eastern United States, Spangled Skimmer (Libellula cyanea), in high speed video clips as it flies and catches prey. At least three other species, and I think a fourth, make cameo appearances in the video as well. Can you spot them all?

If you haven’t seen it already, it’s worth a look. If you have seen it before, it’s worth another look (the video is only two and a half minutes). There is something very calming—almost mesmerizing—about flying dragonflies captured on high speed video.

The Broken Wheel (When Dragonfly Sex Goes Wrong)

I recently devoted a post to the Olive Clubtail, Stylurus olivaceus, but here’s another photo of the species you might find interesting.

The Foot High Club

 

A few years ago this coupling couple of Carmine Skimmers (Orthemis discolor) were flying low over a ditch in Cahuita, Costa Rica. Odonates frequently fly while copulating—they do it all the time, actually—but this was the only instance that I managed to photograph (and end up with something other than an unidentifiable blur). In case you were wondering, the Carmine Skimmer is not a species any reasonable odonatist can expect to see in the Pacific Northwest. Not yet...

Olive Clubtail (Stylurus olivaceus): The Lower Columbia's Gomphid

 

Pacific Northwest members of the dragonfly family Gomphidae—the clubtails, are mostly species of the height of the summer season. Even though daylight hours are waning after the summer solstice, daytime temperatures continue to rise and sunny, dry days are increasingly expected. During this time most gomphids are out in force and doing what gomphids do. One species, however—the Olive Clubtail, Stylurus olivaceus—is just starting to emerge while other gomphids are at the zenith of their adult activity.