A few years ago, John Tuthill was trail running in the Cascade mountains in Washington state when he spotted something dark skittering across the snow.
It was about the size of a wild blueberry, with an elongated body and six legs that moved in a blur.
Tuthill was surprised to see an insect out and about on that cold October day. “I was kind of blown away that there was this animal out running around,” says Tuthill, a neuroscientist at the University of Washington in Seattle. It was a Chionea fly, he later learned. Also known as a snow fly, it could somehow walk around at temperatures well below what most other insects can tolerate.
Now, Tuthill and colleagues have shown that a grisly trick helps snow flies survive sub-zero conditions. When a leg begins to freeze, the insects can rapidly self-amputate it, preventing ice crystals from creeping up into their bodies, the team reports in a paper posted online May 30 at bioRxiv.org.
Many animal species, including spiders, lizards and crabs, can drop a limb or tail to escape a predator (SN: 2/17/22), but the new work is the first to show an animal using this life-saving measure in response to the cold, says Christine Miller, an evolutionary biologist at the University of Florida in Gainesville. The study describes “a new phenomenon that hadn’t been documented before and a very interesting species that we know very little about.”
Snow flies are a type of flightless crane fly, relatives of the “big, spindly, goofy-looking flies that you see bumbling around in your house,” Tuthill says. The insects, which can live up to two months, aren’t easy to study: They can’t be bred in the lab, and they’re tough to collect from the wild. Snow flies can live in alpine areas that are difficult for people to reach, where the threat of avalanche looms.
The best way to find them, Tuthill says, is to spend a lot of time wandering around, looking at snow. Backcountry skiing fit the bill. In an…
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