Signs of life in the winter woods are easy to find. Squirrels scurry ceaselessly and birds mob the feeders. Tracks in the snow reveal mammals large and small. But while winter halts the visible activity of most insects and spiders, visit your local preserve on a sunny winter day and you may encounter the hardy little snow flea.
Look around the bases of trees, often where the snow has begun to melt. If you see what looks like pepper sprinkled all over the snow, look more closely—you may just be looking at snow fleas.
Also called springtails, snow fleas can be found in the leaves lying on forest floors around the world, and not just during winter. One square foot of leaf litter and soil may have many thousands of individuals.
Snow fleas are not “fleas” at all but belong to a primitive insect-like group called Collembola. Unlike most other insects, Collembola don’t have wings. People call them fleas because of their habit of jumping into the air, and “snow” fleas because they’re easiest to see on the surface of the snow.
When snow fleas jump, they’re propelled not by strong back legs like real fleas, but rather by a kind of stiff tail that is tucked under their body and held by hooks. When the snow flea is disturbed, the hooks release and the tail pushes against the ground, launching the animal six inches into the air—hence the name “springtail.” This sudden leaping is a good way to avoid being eaten by some other bug. Relative to their size, the height they jump is incredible. If humans could leap that high, they’d be able to jump over any but the tallest buildings in Chicago!
The snow flea survives below-freezing weather through special chemistry. For winter, it produces proteins in its body that works like the anti-freeze we put in our car engines. The proteins keep ice from forming in the snow flea’s cells. Snow fleas have been found in the coldest habitats on earth, including the high Himalayas and Antarctica.
To solve the problem of winter food shortage, snow fleas eat dead plant material such as the piles of fall leaves just beneath the snow.
Animals of the forest preserves are alive and active during these cold and snowy months. So put on your layers, bring your magnifying glass, and get on the hunt for the jumping, flipping, spring-loaded masters of winter—the snow fleas!
By Brian Winters, naturalist at River Trail Nature Center in Northbrook.