Dragonfly Nymph Shed Skins
Well, heck. I’ve been posting dragonflies for the last week and a half, I might as well use up my last relevant picture set and make it a full two weeks. On June 19, 2011, we all went fishing at the Otter Lake dam, which is where the lake drains into the Sturgeon River. On the downstream side from the dam (which is only about five feet high), there is a concrete walk that is a really nice fishing spot. So, Sam was sitting on the edge of the concrete, reached down for some reason, and came up with one of these hanging on her sleeve.
Well, of course she screamed a little. Wouldn’t you? The thing was an inch long, after all, and looks pretty evil. It was more a matter of surprise than anything else though, and within less than a minute we were looking to see where it came from. It turned out that they were all over the place. We managed to collect ten that were pretty much pristine.
There were bunches more that we didn’t collect that had been damaged in some way. There must have been a huge dragonfly emergence just a few days before we got there, it’s too bad that we missed it.
When dragonfly nymphs emerge from the water, they crawl up onto rocks, plants, or anything that they can get a grip on. Then they split open their backs, and the adult emerges directly from the nymph skin. One of the things that they have to do is transition from breathing water (using the gills in their abdomens) to breathing air (using the tracheal openings in their thorax). That means that they have to develop the tracheal openings, which are just little holes in the thorax that are kind of hard to see. When they emerge from the nymph skins, they pull white threads out of the newly-developed trachea to open them up. These white threads are still visible here:
If you want to see exactly how this works, there is a nice video of dragonfly emergence here (it is part of David Attenborough’s excellent “Life in the Undergrowth” series). Ah, what the heck, let’s try embedding the video.
And, while sorting through the pictures of the dragonfly nymph shells, I found a surprise:
I think that’s a skin from a stonefly nymph (it has two cerci on the end of the abdomen, which is typical for stonefiles. Mayflies, the other most likely candidate, would generally have three). It looks like it crawled out of the water after the dragonfly emerged, and used the dragonfly skin as something to hold onto while it split its own skin and emerged itself.
 Sam used her Barbie spin-casting reel and pole to catch eight fish in about an hour. Mostly rock bass, although I think she caught a smallmouth bass as well. She was pretty excited, especially since nobody else caught any fish that day.
 I normally try to avoid embedding other people’s videos or pictures in these posts, since it’s hard to be sure whether or not there are copyright violations involved. But this one is too good to pass up, and I’m pretty sure that a fully-attributed short clip from a longer work counts as “fair use” if anything does.