Forest Preserve District of Cook County, Illinois
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Cave Animals
Nature Bulletin No. 95   December 14, 1946
Forest Preserve District of Cook County
William N. Erickson, President
Roberts Mann, Supt. of Conservation

Our Senior Naturalist, with a group of scientists exploring one of the big limestone quarries southwest of Chicago, found several dozen strange animals where a small underground stream pours from a seam in the rock wall. They were nearly an inch long, slender, with legs on both ends and snow white. That was a rare discovery because they were Blind Amphipods -- small members of the crayfish family that live their entire lives in secret subterranean waters.

A large part of the United States is underlain by limestone, sometimes hundreds of feet thick, often close to the surface as it is here. Surface water gradually seeps down through crevices in this limestone and along horizontal seams, dissolving the rock to form channels that grow larger and larger. As the centuries pass, these form underground rivers and the caves so common in some parts of this country.

Salamanders, fish, crayfish and several smaller relatives of the crayfish invaded these underground streams in times past, and were able to eke out a precarious living based on the plant and animal debris washed down from the surface. Almost all of these animals, because countless generations of them have lived in total darkness, lack pigment and are white or nearly so. Having no need for eyes, the eyes gradually became mere remnants, or disappeared altogether -- like the whip-sockets on our early auto mobiles.

For ages, many kinds of animals, including primitive man, made their homes in caves or sought shelter there from extremes of heat and cold. Bats hibernate in caves and roost there in daytime during the warmer months -- millions of them in huge caves like the Carlsbad Caverns in New Mexico. They fly swiftly in and out through the darkness without touching the walls or the many obstructions of the twisting channels in these caves, being equipped with especially sensitive ear lobes that time the echoes of the wing beats from the walls -- the world' s first radar.

Incidentally, the fact that bedbugs afflict only bats and humans is supposed to date back to the time when all three lived together in caves. The bedbugs fed on bats in the daytime. The night shift fed on man.

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