Forest Preserve District of Cook County, Illinois
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Snow Insects
Nature Bulletin No. 665-A  February 4, 1978
Forest Preserve District of Cook County
George W. Dunne, President
Roland F. Eisenbeis, Supt. of Conservation

Many animals, or signs of animal life, remain hidden or go unnoticed until the ground is covered with snow. Among the most surprising to appear against its whiteness is a miscellaneous hodgepodge of insects. For a few of these, especially Snow Fleas, our northern winters are their regular season of activity. Other kinds are found alive and more or less active on the snow -- some occasionally, some rarely, and some accidentally. A sunny day in February is a good time to look for them.

Snow fleas usually catch our eye as dark specks hopping about on a melting snow bank. On bright days their bodies absorb enough heat from the sun to keep them active. At night they lie frozen in the snow until the next day.

The snow fleas come nearer to making the whole world their home than any other insect. They are native to every continent as well as the far Arctic and Antarctic, where they are the only insects excepting a few bird parasites. On Alaskan glaciers, a half-mile from the edge of the ice, they have been found feeding on the pollen of trees and the spores of ferns which had blown onto the snow.

Snowfleas jump but they are not true fleas. They belong to a primitive group of inconspicuous, grotesque, wingless insects called Springtails -- so-named because of a spring-like device on the tip of the abdomen which can be bent under the body and snapped downward to hurl the animal in the air -- sometimes several inches or a foot away. Most kinds are less than one-sixteenth of an inch long. Springtails often outnumber all other animal life in damp soils and the leaf mold of woodlands. Sometimes multitudes of them can be seen skipping on the surface of stagnant water. Others may become nuisances in damp basements, in mushroom beds, or in the buckets used to collect sap for making maple syrup.

On bright winter days, Stoneflies are frequently seen crawling about on snow, tree trunks, rocks and bridges along Illinois streams. Their underwater young, called nymphs, develop for almost a year beneath rocks in the rapids and riffles of our cleaner rivers and creeks. Several kinds of them emerge as half-inch long, dark-colored, slender adults -- even while the shores are still edged with ice. They have two pairs of wings but they seldom fly. During the coldest part of the year when other insects are inactive, they feed, mate, and the females lay their eggs in water.

An oddity of the insect world -- a wingless Scorpion Fly -- creeps about on snow in winter and early spring. It has long slender legs and resembles a young grasshopper. They are rare in this region but are occasionally found in great numbers on snow in eastern United States.

The Snow Fly has a body shape and long, hairy legs which make it look like a six-legged spider. Actually, it is a wingless relative of the crane flies -- those long-legged, two-winged insects often mistaken for giant mosquitoes and seen about streams, meadows and at lighted windows. The adults crawl out onto snow in bright sunlight even when the temperature is down near zero. After mating the female works her way down into the snow close to a tree trunk and deposits her eggs. Like other true flies, these hatch, pass through a larva and a pupa stage before the next generation of adults emerge.

The first insect sign of spring to greet visitors to the forest preserves is most likely to be a Mourning Cloak Butterfly flitting among the trees. For a few hours on balmy February days they rouse from their winter sleep in tree holes and under loose bark, then go back in hiding with the chill of evening. Honeybees, too, come out on sunny days and sip the sap oozing from broken maple twigs.

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