Saturday, March 20, 2010

Learning Something New Every Day – Small Winter Stoneflies

The way I look at it, a day where you don’t learn something new is a day wasted. For those of us who are nature nuts, learning something new is pretty easy to do, for there is so much “out there” that no one person can possibly know it all (although, not for lacking of trying). Take, for example, the insect in the photograph here.

I was out the other day checking the trail for animal tracks, not expecting to find much, thanks to all the balmy weather we’ve had of late, but ever hopeful. I was sidetracked by a patch of sunlight along the south-facing bank of the new beaver pond, and found myself lulled into a soporific state, enjoying the sunshine, the birdsongs, and the new green growth all around me. I wasn’t the only one out taking in a few rays; spiders and insects galore hopped and flew all around.

Several of small insects (see photo) chose to use me as a landing platform. I finally decided to photograph one (kind of like trying to photograph a microscopic greyhound at the racetrack) in a somewhat amused attempt to get the things identified. There was something familiar about them; I thought at first they might be some sort of parasitic wasp, but I was keeping an open mind.

When I sent my photograph off to the find folks at BugGuide.net, I included in the description a note that it had two little tails sticking out its nether regions. It dawned on me that these little tails were what was familiar – they reminded me of the two little tails one sees sticking out behind stonefly nymphs (I was no longer thinking “parasitic wasp” at this point). So, I added this observation to my note. The pithy response that came back was “That’s because it’s a stonefly.”

Now, I’ve turned over a lot of rocks in rushing streams and I’ve seen more than my share of stonefly nymphs. If that’s a stonefly, I thought, it’s gotta be the smallest stonefly in the world. This insect measured maybe 5mm from stem to stern, while every stonefly nymph I’ve ever uncovered has easily been two to four times the size of this adult insect. Usually when insects go through The Change, they end up bigger – I’d never heard of one ending up smaller. So, suspicious and curious, I took this stonefly information to my Kaufman’s Field Guide.

And wouldn’t you know! There it was – a tiny little stonefly from the family Capniidae – the Small Winter Stoneflies. Even better, the photo of Allocapnia sp. seemed to fit my insect like a glove. There are 38 species in this genus, and they are the common small winter stonefly here in the eastern United States.

I had to know more.

According to yet another one of my field guides, these stoneflies dare to be different, for they change into adults and emerge for a terrestrial life while winter still has a grip on the world (December to April). They can be seen actively flying around when the air temperature is a chilly 20 degrees Fahrenheit. It’s no wonder they were zipping around in the afternoon sunshine – it must’ve been close to 60!

As juveniles, these little stoneflies fill a very important niche. They are detritivores, or shredders, meaning that they are responsible for chewing up leaves that fall into the streams where they live. If it weren’t for insects like them, our streams, rivers and ponds would be choked solid in only a short matter of time.

Now, I don’t know which species of stonefly my little friends were, and for now I don’t really care – I’m just excited to know that they are stoneflies. Still, at some point in time I’m going to want to know a little more information. Until I can identify the species, my knowledge will be limited. And a quick scan through some of the common names has already piqued my curiosity. Who wouldn’t want to know more about something called “Black Warrior Snowfly,” or “Peculiar Snowfly,” or, my personal favorite, “Sasquatch Snowfly”?

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Ellen Rathbone is by her own admission a "certified nature nut." She began contributing to the Adirondack Almanack while living in Newcomb, when she was an environmental educator for the Adirondack Park Agency's Visitor Interpretive Centers for nearly ten years.

Ellen graduated from SUNY ESF in 1988 with a BS in forestry and biology and has worked as a naturalist in New York, New Jersey, and Vermont.

In 2010 her work took her to Michigan, where she currently resides and serves as Education Director of the Dahlem Conservancy just outside Jackson, Michigan.

She also writes her own blog about her Michigan adventures.



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