Although ordinary-looking, Boreus hyemlis is quite remarkable in that it is active in cold weather. While many insects hibernate in the winter to survive low temperatures, this 5mm long scorpion fly, commonly known as the ‘Snow Flea’, has long legs which enable it to run, and even to jump, across snowy surfaces.
Furthermore, whereas damaging ice crystals may normally form within the body of an insect when exposed to the cold, Snow fleas can supercool by lowering the freezing point of fluids in their cells using special proteins and polyhydric alcohols.
Boreus hyemlis may be seen between October and March on moors, woodland and boggy areas - anywhere there is a lot of moss on which the adults and their larvae feed. The image shown is of a female specimen with the curved ovipositor at the end of its body which she uses to lay eggs at the base of moss plants. These hatch in November, and the emerging larvae forage in the moss before pupating at the end of summer. The wingless adults appear in mid-autumn.
