By Hope Rogers, Trail Walker Contributor
On a bright winter day, have you ever noticed what look like specks of dark soot in the snow, especially at the base of trees? And then, upon closer inspection, the “specks” are crawling and jumping? What are those things?
Those minuscule, lively creatures are a type of springtail, Hypogastrura spp., commonly known as snow fleas. They’re actually with us all year long, and in huge abundance. They can be found throughout the forest, living in leaf litter, in moss and fungi, and around ponds. They even walk on water, their light bodies supported by the water’s surface tension. However, without the white background of snow, their tiny dark bodies, approximately 1/16 of an inch long, are rarely noticeable.
Snow fleas, like fleas, are tiny jumpers. However, they aren’t fleas or even flea relatives. Fleas are parasitic insects; snow fleas are wingless arthropods that never use human or animal hosts. Snow fleas’ jumping mechanism is also different from fleas, which propel themselves upward on powerful legs and toes. Snow fleas have two forked tails, or “furcula,” that they hold folded under them. When they release the hook-like structures that hold the furcula in place, the tails “spring” out, propelling the tiny creatures willy-nilly into the air.
Snow fleas are an important link in the forest food chain. They are decomposers, consuming decaying plant material in the soil, breaking down nutrients into forms that plants can take up. In late winter or early spring, they sometimes form huge colonies, as wide as a yard, devouring the algae that grow on wet, decomposing leaf litter in the melting snow. They are also eaten by slightly larger creatures, including salamanders, daddy long-legs, beetles, and centipedes.
One thing snow fleas must have is moisture. They breathe through their skin rather than through a respiratory system, which makes them vulnerable to drying out. So they move around in search of moist, sheltered locations. Every spring, springtails mate, and the females lay eggs in the soil. Tiny springtail nymphs emerge from the eggs and begin to grow, repeatedly molting their exoskeletons. By winter they have developed into the mature creatures we see in snow.
Snow fleas and other springtail varieties possess a rare characteristic: they make their own “anti-freeze,” a protein that prevents ice crystals from forming in their cells. This recently discovered protein is unlike other known proteins; scientists are studying its structure in the hope of using it in applications such as safely chilling human organs destined for transplant, and perhaps for producing ice cream that never develops ice crystals. Protected by their “anti-freeze,” snow fleas venture out on sunny winter days in search of decaying plant matter and sap oozing from trees.
Although we rarely notice them, snow fleas are all around us on the forest floor, performing their crucial role in the food chain. Look for them on sunny, snowy days, especially in late winter and early spring.