Thursday, December 6, 2012

ID Challenge #4 Answer

Click image for a larger version.
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.

Saturday, December 1, 2012

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.