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Termites are any of a group of small social insects that feed primarily on wood. Although termites are often called white ants, they are not related to ants. They form a separate order, the Isoptera, and are related to cockroaches. There are more than 1,800 known species of termites. Most of them live in the tropics, but they also occur in temperate climates. In the United States there are about 55 species. The smallest termites are workers only % inch (6 mm) long, and the largest queen termites are 3 inches (8 cm) long when full of eggs.
Like ants, all termites live in colonies. The termite society, however, is different from other insect societies because there are as many males as females. Among termites, as in other social insects, there are separate forms, or castes, which perform specific functions in the life of the colony.
Food is constantly interchanged in the colony by mouth-to-mouth and anus-to-mouth exchange. Termites' droppings are not merely waste; they are food and building material and contain messages, such as those that control development.
Most termites eat wood, although paper, leaves, and other plant products are often eaten. Wood-eating termites have certain types of protozoa, or microscopic one-celled animals, living in their intestines. The protozoa are able to digest the cellulose of the wood, which termites are unable to digest. Termites and their protozoa are symbiotic, which means that they are mutually dependent; neither can live without the other. Each wood-eating termite must supply itself with protozoa by anal feeding from other termites soon after it is hatched and again after every molt. The protozoa are lost during molting because the lining of the intestine is shed along with the outside skin. Termites that live on leaves, grass, leaf mold, or other foods containing little cellulose do not need protozoa and do not carry them.
Some termite species prefer to eat damp wood and some prefer dry wood. Some that live deep in desert sand come up to eat cactus. As with the ants, some species are harvesters and some are fungus growers. The harvesters travel in columns in or on the ground to collect green or dried grass and store it in their nests for food. The fungus growers, including some mound-building termites and termites that live in the soil, collect bits of leaves, grass, and decayed plant material and spread them in large chambers in the nest. They then cultivate a kind of mushroom, which they use for food, on this material. The termites keep the fungus carefully pruned to a suitable form and fertilize it with their droppings.
At the proper season, when the temperature and other conditions are suitable, great numbers of newly matured kings and queens swarm out of the termite colony to mate and establish new colonies. Such dispersal flights usually occur in very humid weather, just before or after a rain or even during a rain. Probably because of similar responses to the weather, many colonies of the same species swarm at the same time. Simultaneous swarming allows the males and females of one colony to meet those of other colonies and prevents excessive inbreeding.
Although, in the tropics, swarms may consist of many thousands of termites, probably no more than one in a thousand of the clumsily flying termites survives to mate and establish a colony. The rest are devoured by birds, toads, lizards, and such larger insects as dragonflies.
Termites do not mate in flight. After they alight, they break off their wings and meet in pairs. While swarming, termites are attracted to light, but once they have landed, they are repelled by light and begin to seek cover. The female scurries away to find a nesting place, and the male follows closely behind. If the male hesitates or gets lost, the female stops and waits with the abdomen uplifted, attracting the male with a special scent. Together the king and queen enter a crack or tiny hole in wood or in the soil, depending on the species. They then dig a royal cell or chamber and seal it shut. Finally they mate.
Some wood-eating termites nest in wood, and then: nest cavities develop as the natural result of the insects' eating their way through the wood. Such termites include the dry-wood varieties that may infest buildings at the second story or under the eaves and the damp-wood varieties that eat decaying wood. The common termites of the United States feed on wood but make nests in soil. In various tropical species the nest is a mound above ground level. Mound nests are especially conspicuous in South America, Africa, and Australia, where they are sometimes 15 feet (4.6 meters) high.
The building material of termites is composed of particles of wood or earth mixed with saliva and droppings. It dries to such hardness that in some cases it cannot be easily broken with an ax. Most building, especially that of runways across open surfaces, is done at night under cover of darkness.
Although termite colonies grow slowly in comparison with those of ants, bees, or wasps, they eventually become much larger. In the dry-wood termites the first few eggs are not laid for months, and at the end of one year the colony has less than a dozen adults. Later the queen lays about 100 eggs a year. In contrast, in some tropical species the queen, after several years of increasing reproductive powers, may lay 10,000 eggs a day and eventually become the mother of several million termites. Such a queen is always so swollen with eggs that it cannot walk. Its abdomen, once slender and less than Va inch long, becomes the size of a man's thumb.
Growth and Development
The termite lays a white egg less than l/16th inch (1.6 mm) long. When the tiny termite hatches from the egg, it is in the nymph stage and more or less resembles the adult in form. It has legs, jaws, antennae, and other organs and is able to move about at once and take part in nest activities. Unlike ants, termites have no helpless grub stage, nor do they undergo the radical changes of a pupal stage. However, very young termites must be fed by other members of the colony.
In the course of its growth the nymph changes into a reproductive, worker, or soldier. Apparently, a nymph is capable of becoming any caste, at least up to a certain point in its growth. The form that it assumes depends on the needs of the colony and is determined by chemical substances produced by mature termites.
There are three principal castes of termites: the reproductives, the soldiers, and the workers. Each caste is made up of both males and females, and the number of members in each caste depends on the needs of the colony. Some kinds of termites do not have all three castes.
The reproductive castes of termites include primary kings and queens and supplementary kings and queens to replace the primaries if they die. The supplementary kings and queens are wingless or have short wings that are not useful for flying, but the primary kings and queens are winged for a brief time and can fly out and begin new colonies. The winged kings and queens are dark-bodied and shiny. They resemble flying ants, but they do not have slender waists and their front and rear wings are the same size and shape. In ants the front wings are much longer than the rear ones.
There may be one or two types of soldiers. Soldiers guard the colony from enemies, such as ants, and alarm the other members when the colony is damaged or invaded. The soldiers have a huge head and usually have big jaws. However, instead of oversized jaws, some soldiers have a snout from which they squirt a sticky fluid at intruders. Other soldiers have a thick, nearly square head that they use to plug up the entrances of exposed tubes and galleries in the colony. The soldier's head is dark brown and hard, and the rest of the body is soft and white. Because of their awkwardly large jaws or snouts and oversize head, mature soldiers must be fed by other termites.
In many kinds of termites there is a distinct worker caste. In other kinds there are no workers and all the work of the colony is done by immature forms, called nymphs, which may live for several years before they develop into distinctive adult forms. Both workers and nymphs have soft white bodies. They are blind, timid, and slow-moving and are sensitive to light and dryness.
To understand how a colony of termites can regulate the numbers of each caste, the colony with all its dozens, thousands, or millions of members must be thought of as one great organism. The king and queen are the parents of all the members of the colony, but they do not rule the colony. They control its activities in only one way. As long as they live, they produce chemical substances that other termites lick from their body. The termites that receive the substances are probably stimulated to produce similar substances in their own body. In the continual exchange of food that is necessary in a termite colony, these chemicals are passed to all members of the colony, preventing any of the nymphs from developing into kings and queens. If either the king or queen dies, however, this inhibiting chemical is no longer produced, and within one or two weeks one or more of the secondary reproductives has matured and replaced the dead primary. In many species, secondary reproductive females lay more eggs than the primary queens and the colony grows faster after the original queen has been replaced. The number of soldiers, in comparison with the number of workers in a colony, is controlled by inhibiting substances that are given off by soldier termites.
In addition to substances that prevent development, there may be body substances that stimulate development of certain forms. Such a stimulating substance may be necessary to allow young winged kings and queens to be produced at the proper season of the year in spite of the presence of a living king and queen.
Although termites are generally thought of as destructive, they are useful in nature. They clear dead and fallen wood from forest floors and quickly return organic material to the soil. The types that live in the ground are important in loosening and aerating the soil. In some parts of the world the hard material of termite nests is used as flooring and building material.
In civilized areas, termites are far more harmful than beneficial. Losses due to damage and money spent on control and preventive measures amount to millions of dollars each year. It is estimated that in southern California alone, termites cause a yearly loss of 20 million to 25 million dollars.
Termites have hindered the development of many tropical areas because they destroy books and documents, as well as buildings, furniture, works of art, linens and clothing, leather goods, and telephone and power poles. Sometimes, termites live in ships below the waterline, and they have even been known to chew their way through ivory and concrete. In. France they damage grapevines; in India they eat tea plants; in Java they destroy teak trees; in Australia they damage timber; and in Africa the harvesting termites destroy lawns and standing field crops.