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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
CAVE ANIMALS
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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Update: June 2012
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