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.