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The Woolly Bear
Nature Bulletin No. 314-A September 28, 1968
Forest Preserve District of Cook County
Richard O. Ogilvie, President
Roland F. Eisenbeis, Supt. of Conservation
THE WOOLLY BEAR
Many children get their first glimpses into the fascinating world of
natural history from watching the Woolly Bear Caterpillar -- the one
with the dense even coat of "fur" which is rich red-brown in the
middle and black on both ends. This is the larva of the Isabella tiger-
moth and occurs in great numbers from coast to coast. It is commonly
seen on sunny autumn days and always seems to be in a hurry,
scurrying across roads, sidewalks and bare places in search of some
safe place to hide before winter. When disturbed or picked up, it curls
into a tight bristly ball and "plays dead". That is why it is called the
Hedgehog Caterpillar.
There are 13 segments in its body, not counting the polished black
head, but the rear two are so joined that they look like one. On each of
the first three is a pair of true legs with little shiny claws. The next
four segments each have a pair of false legs, called "prolegs", which
are merely fleshy extensions of the sides of the body, and at the rear
end is a "prop leg". Because it cannot see far with its tiny eyes, you
may observe one clinging to a leaf while the front end rears up and
feels in all directions for another place to go.
The segments are thickly studded with little wart-like tubercles, each
of which bears a tuft of coarse stiff hairs. There is a superstition that if
the middle band is narrower than either of the black bands on front
and rear, then the coming winter will be severe; if the three are about
equal it will be average; and if the red-brown band is widest, the
winter will be mild. Almost invariably, the first three or more
segments are black but occasionally all the rest are reddish. Most
scientists agree, however, that this caterpillar is not a weather prophet;
that the relative amounts of red and black are due to conditions of
temperature, and perhaps moisture, during its early life. Experiments
with some other insects, such as fruit flies and cabbage butterflies,
show that their markings vary according to the temperatures at which
they are raised.
The woolly bear, unlike many caterpillars, feeds on a wide variety of
plants such as grass, clover, plantain, dandelion, spinach and cabbage.
There are two broods: one in June or July, and another in September.
The latter are the ones we see in autumn on their way to protected
places under boards, logs, boulders, or in crevices, where they curl up
and hibernate. In early spring they come out, feed for a short while,
and then each spins an oval cocoon of silk interwoven and padded
with its own hairs. The first adult moths emerge in late May. They are
night fliers with three rows of six black dots on the abdomen and a
wingspread of almost two inches -- tawny yellow wings with a few
dark spots; the hind wings sometimes tinted with dull orange.
There are many, many species of tiger-moths, all with stout spotted
bodies, but they vary greatly in wing colors and markings. Most of our
other common hairy caterpillars are also in this family but pass the
winter in the pupa stage instead of hibernating as caterpillars. Among
them are the Fall Webworms, the gay Harlequin Caterpillars that
usually feed on milkweeds, the Salt Marsh Caterpillar which is
abundant over most of North America as well as in salt marshes, and
the Yellow Bear. The latter has a dense uneven coat of long hairs
which may be pale yellow, whitish or reddish. Altho it feeds on many
kinds of plants it is frequently found in our flower gardens and
greenhouses.
The Indians had the answer to caterpillars. They ate 'em.
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