Curious Nature: Some bugs are at home on top of the snowpack

Have you ever been outside on a winter day and seen tiny black specks bouncing around or maybe even a “spider” crawling across the snow? If so, then you have experienced two of the smallest creatures that are active on top of the snowpack. Did you take a minute to wonder what they are and how they can possibly survive in this cold environment? I did, and to my amazement, I discovered that some of these seemingly unimportant animals can even provide a benefit to humans!

I am probably more nature-nerdy than the average person on the ski hill, but when I first really paid attention and saw one of these pencil-eraser-long “snow spiders,” I had to know more about it.

This little six-legged creature, called a snow fly, is not a spider at all but a wingless insect belonging to the family that we call crane flies. (This group is made up of long-legged flies that resemble huge mosquitoes and are sometimes called mosquito eaters, even though they don’t eat mosquitoes.) Scientists don’t know much about these snow flies,but have found that they are relatively long-lived (about two months as an adult), that they probably don’t eat as adults and that they spend most of their time under the snow in the leaf litter and dead grasses. They only come to the snow surface on days when temperatures are near freezing and then only to look for other holes in the snow where they might find a mate or a good place to lay eggs. When they are out walking, they cruise along at 4 feet per minute, which is pretty fast for a quarter-inch insect in the cold! They don’t have wings since they wouldn’t function at such cold temperatures and would be in the way when they are underground.

My investigations of the snow fly led me to uncover information about another small local critter that lives outside during the winter. The above-mentioned little black specks, which can sometimes be found in large groups in footprints or other depressions in the snow, are commonly called “snow fleas” because of their jumping behavior. They are not actually related to fleas at all and, although they also have six legs, are not even classified as insects (although they used to be). They are harmless arthropods (animals, like insects and crustaceans, with jointed legs and a hard exoskeleton) called springtails who are likely feeding on small plant debris trapped on top of the snow. Their name comes from a spring-like structure (a furcula) on their tail that shoots them into the air by several inches (up to 100 times their body length since they are less than 1⁄16-inch long). They are so hearty that they have even been found living near the poles.

Both types of animals benefit from living during the cold of winter because of the decrease in predators, but their bodies need to have adaptations that allow them to survive freezing and below-zero temperatures. They minimize the moisture in their bodies (so it doesn’t freeze and cause damage), and they produce glycerol internally (which works as antifreeze). Also, their enzyme systems are designed to operate at low temperatures. In fact, adult snow flies are so specialized for the cold that they can’t function at temperatures much above freezing. Scientists have also discovered an antifreeze protein in snow fleas that may have an application for human organ transplants.

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So, although these little creatures may seem insignificant to us, they do have a role in the ecological system and they might just teach us something that will benefit our lives.

Jeanine Junell Kenney is lead naturalist for Walking Mountains Science Center. She spends her time learning and teaching about the natural world, as well as exploring it whenever she can.