Female Snow Fly

2024 January 28

Sam went out snowshoeing and caught this snow fly for me on January 10, 2024. She put it in the refrigerator for me to keep it from overheating until I got home. We’ve had pictures of these insects a few times before, first on January 12, 2008, and then a pair of them on January 3, 2015. And most years, we see one or two sometime in the second or third week of January, generally when the temperature is just a bit below freezing. This is the first time I’ve gotten a chance at one with the high-magnification lens, though, so let’s have a closer look:

As I noted in the previous occasions , these are a species of crane fly that has adapted to very cold conditions, so that they can walk around on the snow without freezing solid. They have lost their wings, so calling them “Flies” is kind of inappropriate, but at least this lets us know what they are related to. We can see from the fact that her abdomen comes to a pointed tip that this is a female, the males have big claw-like claspers on their abdomens. We can also see the two little projections on her back that are all that is left of the ancestral wings. The reason she is so plump, is that she is stuffed full of eggs.

The first few photos were taken inside of the jar that Sam caught her in, but as we can see here she was keen to escape.

So, I took her back outside and released her in the snow. She immediately then began pacing across the snow to continue her interrupted trip to find a good place to lay her eggs.

In some ways, she was easier to photograph in the snow. She walked in a slow, measured sort of way in a straight line so that I could line up a reasonably clear shot of her head.

Adult snow flies evidently don’t eat, although they do drink snow-melt a bit to keep from drying out.

And since the last time I posted one of these, a new website has been created that is specifically devoted to snow flies: The Snow Fly Project. If I had known about this site before I let her go again, I could have sent her in to contribute to their research project. I think we have passed our local window of opportunity for snow flies, though, so we’ll have to try again next year.

At the very least, I should get a bunch of those little centrifuge tubes that they recommend for shipping snow flies in. They look handy for catching insects to bring home in general, and I can just toss a bunch in my coat pocket.

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