Keith Jarvi, UNL Extension, describes an interesting critter that we may see hopping in the snow this winter. Fortunately, it is "not a problem," so rest easy if you see one - or many.
What is a Snow Flea?
Recently, someone brought snow fleas to the extension office for identification. Most folks have never seen snow fleas or even heard of them. As their name suggests, snow fleas are tiny arthropods that are active outdoors during the wintertime. If you are outside on a sunny winter day, take a close look at the snow, especially where it has melted a bit around the base of trees or near the house foundation. Snow fleas are tiny, (1/32 - 1/16-inch), gray to purplish in color, and look like someone spilled pepper on top of the snow. If you look even more closely you may see them moving. Folks also may find them on sidewalks and concrete near their home, but the snow fleas are easier to see when their dark bodies contrast with white snow.
Most springtail species are not active in the winter, but one species - the dark blue springtail (Hypogastrura nivicola) - is active and is commonly known as the snow flea. They produce a unique antifreeze-like compound in their bodies that allow them to be active when other arthropods are dormant. A researcher at the University of Wisconsin is studying an edible antifreeze made from gelatin, which is very similar chemically to the one found in snow fleas. Eventually, this compound may be used to keep ice crystals from forming in ice cream.
Springtails are ancient organisms - fossils have been found and dated to be 400 million years old. They have six legs, like insects, but entomologists separate them from true insects because of their internal mouthparts and other structural differences. They have now been assigned their own classification as Entognatha Hexapoda, since they have many non-insect features.
Springtails do not have wings, but use a tail-like apparatus to jump (hence, the name springtail). This fork-like structure, called a furcula, is attached to the hind end and folds under the body. Upon release, the furcula pushes the springtail into the air allowing it to jump short distances.
But is it Really a Flea?
Despite its name, the snow flea is not a flea, and it does not bite or feed on humans or animals. Springtails live in damp areas of the soil, or under leaf litter, where they feed on fungi, algae, and decaying organic matter. Springtails are extremely common outdoors in the soil. It is difficult to calculate numbers, but there can be thousands to millions of springtails in a cubic meter of soil.
In summer, they may reproduce in tremendous numbers in moist soils with high organic matter. Occasionally they may migrate into houses if the weather is hot and dry and will usually be seen in areas where there is moisture like sinks and bathroom drains. This is a nuisance but they will soon die after entering buildings.
Springtails will find a home in the soil of houseplants after migrating in or be brought inside with plants that were outdoors in summer. They do little, if any damage to the plant. Usually, allowing the soil to dry down a little more can reduce the problem.
Snow fleas develop under snow cover, feeding on leaf litter and soil. When the temperatures warm, thawing snow forms channels from the soil to the snow surface along trees, old flower stems, and other vertical structures. The snow fleas may be so numerous as to show up like dirty spots, often in depressions made by footprints. A closer look will reveal the swarming, hopping critters. No one quite knows why this behavior occurs. It may be triggered by overcrowding in the litter beneath the snow, and as a possible response to warmer temperatures above the snow layer. Some may find their way back to the soil through the channels, but many will die.
Since we have had little snow cover to insulate the soil surface and some extreme temperatures, this may not be the best year to see snow fleas. You can look for them after we get one of our typical Nebraska February-March blizzards.
Much of this information comes from a Colorado State University fact sheet no. 5.602 "Springtails" by W. Cranshaw.