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Mites
Nature Bulletin No. 491 April 27, 1957
Forest Preserve District of Cook County
Daniel Ryan, President
Roberts Mann, Conservation Editor
Ramon Swishe, Senior Naturalist
MITES
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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Update: June 2012
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