Forest Preserve District of Cook County, Illinois
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Centipedes and Millipedes
Nature Bulletin No. 244-A   November 12, 1966
Forest Preserve District of Cook County
Seymour Simon, President
Roland F. Eisenbeis, Supt. of Conservation

Our dislike for things that crawl in dark damp places seems to have come down to us from the dim past; perhaps from the days when our ancestors shared caves with them. Many of us shudder when we come across one of these creatures in damp basements, in gardens, under rocks and rotting logs, or among leaves and trash. Among these dwellers in darkness, besides worms and slugs with no legs, insects with six legs, spiders and daddy-long-legs with eight, and pill bugs with fourteen, there are two sorts with a multitude of legs. These are the Centipedes and the Millipedes. They are not worms but are long slim animals with many legs and segmented bodies enclosed in jointed shells.

The centipedes, of which about 1200 kinds are known in the world, have one pair of legs attached to each body segment -- from 12 to 60 pairs according to the kind. Most of them feed on insects and other small prey which they kill or paralyze with poison injected through the claws on the front pair of legs. Some large tropical species, which become a foot long or more, can inflict painful bites but our native centipedes are almost harmless.

While others are outdoor creatures, the House Centipede is often seen rushing over walls and floors of houses when a light is turned on, or trapped in a bathtub or sink -- to the dismay of a housewife. Its flat ribbon-like body is only an inch or so long, with a pair of very long slender "feelers" on the head and 15 pair of long legs arranged along the sides. the last pair being more than twice the length of the body. It is grayish yellow in color, marked with three dark lengthwise stripes, and the legs are banded with white. It runs rapidly but often halts, remaining motionless, and then races for concealment in some crack or crevice. It is the only centipede that thrives and breeds in houses, often wandering into the upper floors. There have been a few instances of bites by them but the symptoms are not severe. Actually, they are beneficial because they feed upon cockroaches, flies, moths, spiders and other small creatures about the house. The tiny whitish Garden Centipede, found in cracks in soil and about the roots of plants, is only a little over 1/4 inch long when full-grown and has 12 pairs of short legs.

The millipedes, or Thousand-leggers, are among our most primitive land animals. Their fossils, some over a foot long, are found among the swamp plants that went into the formation of coal. They differ from centipedes in having rounded bodies and two pairs of short legs on each joint or segment, except the first three which have only one pair each. Some kinds may have over 200 pairs, and there are about 1300 kinds known over the world, ranging in length from a twelfth of an inch to 8 inches. Although they sometimes invade houses, they are entirely harmless to man and feed on decaying vegetable matter, on decaying wood, and often on the tender roots of plants or even green leaves that touch the ground. Sometimes they tunnel into the fleshy parts of garden crops and do damage.

Millipedes crawl with a slow graceful gliding movement unlike the rapid wiggling of the centipedes. Waves of movement pass down the rows of legs like a column of soldiers a little out of step. V~/hen touched, they curl up and "play dead". In our Chicago woodlands, under fallen leaves and fallen logs, we often find a large mahogany- brown one, called Spirobolus, which is about as big as a king-size cigarette and has over a hundred pairs of legs. To protect itself from enemies, it gives off an offensive odor from special stink glands -- strong enough to kill small insects.

There are also two-legged stinkers.

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