Because insects need warmth in order to function, they are not the sort of thing you’d expect to see on a Winter day. But nature has many “rule breakers” and the Winter Snowfly is one of them.
Similar to dragonflies, damselflies, mayflies, and caddisflies – snowflies spend most of their life as aquatic larva. While most aquatic insects develop fastest in warm weather, Winter Snowflies do the opposite.
Why don’t these insects freeze to death? The secret lies in the production of “antifreeze” that disrupts the formation of ice crystals in the insect’s haemolymph (blood), allowing the body fluids to remain liquid at temperatures several degrees below freezing.
Once out of the water, snowflies rummage about in search of mates. Males attract females by drumming their rear end against the snow and ice. Females feel, rather than hear, the vibrations made by calling male.
Winter Snowflies have very particular water quality requirements, and are among the first animals to disappear from polluted or degraded streams and lakes. As such, they are frequently used for biomonitoring.