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
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
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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Update: June 2012