Fascinating Facts About Snow Fleas

At the end of a long, cold, nearly bug-free winter, it's always a thrill for the insect enthusiasts among us to spy a group of snow fleas hopping merrily in the melting snow. While few may be fans of the common flea, snow fleas aren't really fleas at all. Like spiders, scorpions, horseshoe crabs, and katydids, snow fleas are actually arthropods—specifically of the springtail variety.

What Do Snow Fleas Look Like?

In North America, most snow fleas you're likely to come across belong to the genus Hypogastrura and are usually blue in color. Snow fleas tend to aggregate around the trunks of trees. They've been known to gather in such great numbers that sometimes they make snow appear black or blue.

At first glance, snow fleas may look like motes of black pepper sprinkled on the surface of the snow but upon closer inspection, the pepper looks as if it's moving. While they're tiny (reaching only two to three millimeters in length) and jump around as fleas do, a closer look will reveal that snow fleas have a similar appearance to other springtails.

Why and How Do Snow Fleas Jump?

Snow fleas are wingless insects, incapable of flying. They move by walking and jumping. Unlike other famous jumping arthropods like grasshoppers or jumping spiders, snow fleas don't use their legs to jump. Instead, they catapult themselves into the air by releasing a spring-like mechanism called a furcula, which is a tail-like structure that's folded underneath the body (hence the name springtail).

When the furcula releases, a snow flea is launched several inches in the air—a considerable distance for such a tiny bug. Although they have no way to steer, it's an effective way to flee potential predators quickly.

Why Do Snow Fleas Gather on the Snow?

Springtails are actually quite common and abundant, but they're so tiny that they tend to blend in and go unnoticed. Snow fleas live in the soil and leaf litter where they munch away on decaying vegetation and other organic matter, even during the winter months.

Remarkably, snow fleas don't freeze in the winter thanks to a special kind of protein in their bodies that's rich in glycine, an amino acid that enables the protein to bind to ice crystals and inhibit them from growing. The glycine (which works much in the same way as the antifreeze you put in your car) allows snow fleas to remain alive and active even in subzero temperatures.

On warm and sunny winter days, particularly as spring approaches, snow fleas make their way up through the snow, likely in search of food. It's when they gather in numbers on the surface, flinging themselves from place to place, that they attract our attention.

Sources

• Cranshaw, Whitney. "Springtails." Colorado State University.
• "Springtails and Snow fleas." Insect Diagnostic Laboratory, Cornell University.
• Kline, Katie. "Snow fleas: helpful winter critters." Ecological Society of America. January 28, 2011.
• Lin, Feng-Hsu; Graham, Laurie A.; Campbell, Robert L.; Davies, Peter L. "Structural Modeling of Snow Flea Antifreeze Protein." Biophysical Journal, March 1, 2007.
• Hahn, Jeff. "Snow fleas are conspicuous but harmless." University of Minnesota Extension, March 26, 2014.