Last week, we learned about the unusual mating behaviors of tiny hibernal insects called snow scorpionflies (January 23, 2012, Dashing through the snow: Snow scorpionflies). We now visit another tiny arthropod often seen cavorting on snow banks on sunny winter days. Snow fleas, or springtails, are hexapods, tiny six-legged relatives of true insects. They belong to a part of the arthropod clan called the Collembola and are among the most ancient of six-legged creatures. Collembola have been on the planet for 380 million years, roughly 30 million years before the first animals with backbones moved from the primordial sea to the land.
The springtails depicted in this bug of the week belong to the family Sminthuridae. Cat fleas, dog fleas, even bird fleas, conjure an image of small, black, jumping, biting insects. Snow fleas are quite different. Instead of living as external parasites on other animals, snow fleas and other springtails eat tiny plants, decaying vegetation, bacteria, and fungi. On one occasion I found a large colony of springtails happily living inside the water tank of someone’s commode feeding on a layer of biofilm. What a surprise the chagrined homeowner had each time the toilet was flushed! At certain times of the year, springtails become super abundant on the surface of the soil, on pools of calm water, or on banks of snow. In winter, snow fleas multiply on the forest floor and move about despite winter’s chill.
To operate at subfreezing temperatures that would otherwise halt winter frolics, snow fleas evolved a protein that acts like antifreeze and prevents ice crystals from forming in their tissues. They can reach amazing densities and their dark coloration makes them quite apparent on patches of snow. The propulsion system used by snow fleas and other springtails differs from that of their insect relatives. True fleas such as cat and dog fleas have a flexible protein called resilin in their legs. Resilin is compressed and stores energy that is released in a split - second burst to power the jump. Snow fleas and many other springtails have an odd forked shaped appendage called a furcula. The furcula is tucked beneath the body most of the time and held in place by a clasp called the retinaculum. When the snow flea wants to leap, the clasp releases the furcula just like a catapult and the springtail is propelled through the air. As you enjoy your winter walks, stop by a snow bank and try to catch a glimpse of these tiny high jumpers.
Two excellent resources, “The Insects: An outline of Entomology” by P. J. Gullen and P. S. Cranston and “Structural Modeling of Snow Flea Antifreeze Protein” by F. Lin, L. Graham, R. Campbell, and P. Davies were used in preparation of this episode.
To learn more about snow fleas and other springtails, please visit the following websites: