Forest Preserve District of Cook County, Illinois
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Autumn Insects
Nature Bulletin No. 238   October 2, 1982
Forest Preserve District of Cook County
George W. Dunne, President
Roland F. Eisenbeis, Supt. of Conservation

AUTUMN INSECTS
With the coming of October and its chilly nights, all cold-blooded animals become numb or sluggish except during the middle of the day when the warming sun rouses them to wakefulness and quickens their movements. Insects and spiders, especially, seem to sense that their time is short and that they must prepare for winter or have a final fling in the sunlight before they die.

Beneath stones and fallen logs, caterpillars are busy building cocoons, and spiders are making silken tents and cocoons in which they lay masses of eggs. The mud-dauber and yellow-jacket female wasps, and the blow flies, crawl between the screens and windows of our houses seeking warm protected places, and field crickets invade our basements.

One of the best known of all autumn insects is the Wooly Bear caterpillar of the Isabella Tiger Moth. It is closely covered with rosettes of bristly hairs, like an evenly-clipped coat of fur and. according to legend, the kind of winter we will have is foretold by how much of its two ends are black and how much of Its middle is reddish brown. At this season it always seems to be in a hurry -- scurrying across roads, sidewalks and bare places -- hunting a protected place where it may curl up and hibernate. It often wakes and crawls about on warm winter days and it Is one of the earliest signs of spring.

In late summer, large green katydids hidden among the leaves of trees and vines sang their melancholy choruses from dusk until dawn. Now, on mild evenings, only an occasional one is heard rasping hoarsely. Presently a hard frost will kill the last one and only their eggs buried in soft bark will survive to produce next summer's katydids.

In the fields on warm days we hear the songs of other kinds of katydids. Down amongst the grass, fallen leaves and around buildings, male crickets of several kinds chirp both day and night. They sound like the string section of an orchestra: some shrill and twittering; some strumming in sedate cadences; rarely, the deep froggy chirps of a mole-cricket. However, as it becomes colder during the night, their voices change like those of boys who are just beginning to shave -- the chirps are pitched lower and occur at longer intervals.

The grasshoppers are active only in daytime. On fall mornings they may be found clinging to a weed or grass stem, or on the ground -- stiff with cold. Later they crawl slowly to the top of the weed, or onto warm stones and pavements. or up on the sunnysides of trees, fences and buildings where they soon become active enough to jump or fly. An afternoon walk across a meadow is often like a boat trip across a lake, with waves of grasshoppers flowing away on either side. Only their eggs, laid in the ground, survive the winter.

Wild fruit of many kinds -- grapes, cherries, plums, haws, crabapples and elderberries -- still hang dead ripe and sweet, or lie crushed and fermenting on the ground. These attract hordes of butterflies, moths, wasps, bees, ants and flies. The Red-spotted Purple and the Violet-tip butterflies are most common, sipping juice through their long tongues as they slowly open and close their wings. Whole processions of ants carry juice and bits of fruit back to their colonies, and there are swarms of many kinds of flies. Most numerous are the large loud- buzzing Blue Bottles and clouds of the tiny, gnat-like, red-eyed Fruit Fly.

There's a lot to see and hear if you take a walk on a sunny autumn day.


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