Snowfleas are such remarkable little arthropods that they merit at least an annual post. The recent warm weather brought them up out of the leaf litter to the surface of the snow, where they constantly hurl themselves from one spot to another. If you don’t mind getting your knees wet, you can watch as snowfleas tuck their head down and catapult themselves through the air. Just before launching themselves, the snowflea everts three anal sacs from its anus. When the snowflea lands, these sticky appendages act like automobile air bags, absorbing the shock of landing as well as preventing the snowflea from bouncing around. There may be another function that they perform, but it is not known at this time what that might be. While there are many genera of snowfleas, only species in the genus Hypogastrura possess anal sacs.
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