Researchers from the Department of Physiology and Biophysics at the University of Washington in Seattle have discovered something special about the survival strategy of the snow fly (Chionea spp.), a flightless cranberry fly that lives in the boreal and mountainous regions of the northern hemisphere. In a paper titled “Snowflies Self-Cut Off Frozen Limbs in Subzero Temperatures,” published in the journal Current Biology, researchers detail how the extreme act of flying occurs by, as the name suggests, self-cutting off frozen limbs along with the snow. Survive in sub-zero temperatures.

Snowflies can remain active in cold conditions: they have been observed on snow at ambient temperatures down to -10°C. This differs from most insects, which become physiologically deficient at temperatures below the freezing point of water.

Citizen scientists in the form of skiers and climbers have been recruited to collect snowflies in remote mountain regions of the Pacific Northwest, where the insects dart through fresh snow near the tree line. They collected 256 adult snowflies, 20% of whom were missing one or more legs at the time of collection.

Using thermal vision, researchers noticed that snowflies retained the ability to walk even at an average body temperature of -7°C. At this temperature, ice crystallization begins to form in the snow fly’s body fluids, and this ice rapidly spreads from the limbs.

Snowflies usually survive this crystallization and quickly cut off their legs so that the ice crystallization can spread throughout their bodies. The reaction must be fast, as the crystallization that begins in the leg can reach vital organs in half a second.

Self-amputation of the leg occurs sequentially at the joint between the femur and the spit. Self-amputation of limbs for rescue purposes is common in cranes, but this usually involves a predator and is often triggered by mechanical stimuli.

Snowflies, in contrast, do not respond to twitching or mechanical prodding of their legs. Instead, the researchers suspect that leg amputations in snowflies may be triggered by thermosensory neurons that detect temperature changes as ice crystallizes.

Although the snowfly’s habitat is extreme and can sometimes lead to amputation, there are some distinct advantages to living in such an environment. There are almost no other animals around them, including potential predators of snowflies. Eggs laid under the snow are rarely disturbed, and snowflies mate clearly visible on the snow surface for 30 minutes or more.

No matter how safe and secluded snow fly habitats are today, our time to examine them may be limited. Human-caused climate change is transforming high mountain ecosystems: Washington is on track to lose 46% of its late-winter snowpack by the 2040s and 70% by the 2080s.

The loss of snow cover is predicted to increase thermal variability, resulting in lower temperatures under snow where snowflies lay their eggs. Cooler temperatures and increased freeze-thaw cycles can also harm the plant life that snow fly larvae consume in the spring and summer. A radical transformation of the biome would most likely lead to the complete extinction of species. Source