Forest Preserve District of Cook County, Illinois
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Nature Bulletin No. 491   April 27, 1957
Forest Preserve District of Cook County
Daniel Ryan, President
Roberts Mann, Conservation Editor
Ramon Swishe, Senior Naturalist

Spiders, scorpions, daddy-long-legs, ticks and mites are creatures known as arachnids. When adult they have eight legs. Insects have six. Mites and ticks differ from spiders by having the head, thorax and abdomen all fused into one oval-shaped baglike body. Throughout the world, many thousand species of mites have been identified and every year new kinds are found.

Mites vary greatly in appearance and habits. They range in size from those 90 small that they cannot be seen without the aid of a microscope, up to some which are about one-half inch long. Some of the tiniest are wormlike and suck the juices of plants, causing blemishes and galls. Other pigmies live in the breathing passages of bees. Mites vary in color from white and pale yellow, gray or green to brilliant red or orange.

Mites have three stages in their life history: egg, nymph and adult. A few species bear their young alive but, generally, the female lays from two dozen to a hundred or more eggs. From the egg is hatched a nymph much smaller than the adult but similar in appearance except that, in most species, it has only six legs. The nymph feeds, grows and, from time to time, sheds (molts) its tough outer covering when that becomes too small. From the last molt emerge an eight-legged fully equipped adult.

Some mites live in the ground; others in surface litter where they feed on tiny insects or on decaying matter. Some, including several gaily colored kinds, live and swim in fresh water; others in salt water. Some are parasites that live on the outside of animals' bodies but some burrow into the body. Species such as the soil mites, and those that prey on weevils or other injurious insects, are beneficial. Many, however, are serious pests in gardens, truck farms, orchards, greenhouses, homes, places where foods are stored, on poultry and on wildlife. There are few kinds that are dangerous because they transmit certain diseases or cause skin injuries.

In spring, little red mites are often found on freshly turned soil in gardens and fields. These may be chiggers or they may be pests which feed on beans, strawberries, clover or other plants, causing the leaves to curl, turn yellow and die. Another mite, called "the red spider", annually does much damage in orchards and to other trees and shrubs. There are numerous species named for the kinds of forest and shade trees, grains, and foodstuffs they attack. It has been difficult to control the "plant mites" because of their well-protected breathing apparatus, their natural immunity to some poisons, and their tendency to build up resistance to others.

Poultry mites usually hide in the henhouse during daytime and attack the fowl while roosting. One kind sucks their blood; another irritates the skin and causes the bird to lose its feathers; a third causes the feet and legs to become inflamed, swollen and scaly.

A number of mites are parasites on man. The tiny hair follicle mite, found on the nose and ear, is harmless but the itch mite, which burrows under the skin, causes intense itching and scabies or mange. Some species are known to transmit diseases such as Texas fever, yellow fever, and a typhus-like disease. The worst pest is the chigger mite or "redbug" which, in some countries, carries scrub typhus. The adults are harmless but the nymphs attach themselves to a person's skin, suck blood, and cause great discomfort.

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