Snow Fly

While snowshoeing high, high in the mountains, on top of snow measured in feet, we came across what we thought was a spider. Instantly puzzled, we wondered what the heck a spider was doing walking across the snow on a not-at-all-warm day. Had we taken the time to count its legs, we would have known that it wasn’t a spider at all. Luckily I took pictures.

And because I geek-out over this kind of stuff, I had to figure out what it was. Drum roll, please…it was a snow fly. A snow fly? Who has ever heard of such a thing? Clearly not me. And in all the time I’ve spent in the mountains in winter I’ve never come across one.

Apparently these wingless flies are present in montane environments across North America, Asia, and Europe. They spend most of their adult lives in the subnivean* environment (new word alert!) making good use of mammal burrows and cavities in the snow created by rocks, fallen logs, and vegetation. The little research done on these flies reveals that adults most likely don’t eat at all, and only drink water from melted snow. What do the larvae eat? They are coprophagous** (new word alert #2!).

Aside from their winter strolls on the snow, high in the mountains, snow flies are different from most insects in other ways. Opposite from most other insects, snow fly larvae grow in the summer and pupate in the fall. The adults mate in the winter, which, scientists believe is one of the reasons they leave the relative “warmth” of the subnivean zone and go for a stroll. They are looking for a mate.

* the area between the surface of the ground and bottom of the snow

**feeding on the feces of  other animals