Termite

I

Introduction

Termite, common name for numerous species of social insects that can damage wooden structures such as furniture or houses. Of about 2000 known species, most are distributed in tropical countries and some inhabit the temperate regions of North and South America; two have become established in southern Europe. Termites are known also as white ants, a misnomer based on superficial similarities in the appearance and habits of these two insect groups. True ants belong to a more advanced insect order that includes also the bees and the wasps. Termites are relatively primitive; they have thick waists and soft bodies and undergo incomplete metamorphosis (see Insect: Metamorphosis). Nevertheless, they have developed remarkable patterns of social behavior that are almost as elaborate as those of the ants, social bees, and wasps.

II

Termite Castes

No solitary termites exist. A colony may number from 100 to more than 1 million termites. Excluding the immature forms, called nymphs, a colony consists of several structurally differentiated forms living together as castes with different functions in community life. In socially advanced species, three principal castes exist: the reproductives, the soldiers, and the workers. Both the reproductives and the soldiers occur in two or three distinguishable forms, each specialized for a role in the division of labor in the colony. All forms comprise individuals of both sexes, but only in the reproductives do the sexual organs undergo complete development.

Among the reproductives are dark-colored males and females with fully developed wings and compound eyes. At maturity, they leave the parental nest in swarms. After the flight, they shed their wings and mate. A new colony is then established by a male and female who become primary reproductives, that is, the king and queen, whose sole occupation is the production of eggs. Termite kings and queens are longer-lived than other termites, and the queens are larger than other members of their colony. In certain tropical species, the king and queen live for ten years, and the queen grows to an enormous size, sometimes as much as 20,000 times the size of the worker. The abdomen becomes so distended with eggs that the queen is unable to move about. The eggs are laid at a prodigious rate that totals about 30,000 a day in some species. Most termite colonies have only one royal pair.

Apart from the reproductives, all castes are sterile and wingless and have whitish bodies. Typically, the workers constitute the most numerous caste and are the smallest of the adult forms. Workers build and provision the nest, tend the eggs, and feed and groom all the other inmates of the community. In some species, no true worker caste exists; undifferentiated nymphs do the work in the colonies of such species. All species have soldiers with greatly enlarged heads. The soldiers of certain species are equipped with huge jaws for defense of the colony; in some species, the soldiers have long snouts, from which they can eject a sticky, poisonous substance to envelop an enemy and render it helpless.

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Caste differentiation was long believed to be hereditary, but investigations have since demonstrated that nymphs may develop into specialized forms as the need arises within the colony. Hormonelike substances secreted at the body surfaces of the royal pair serve to inhibit the production of primary reproductives. These substances, which are licked off by the workers in the process of grooming, are transmitted, probably with food, to other members of the colony. In the absence of these inhibitory exudates after the royal pair dies, nymphs at a particular stage in their molting cycle rapidly develop reproductive organs and become fertile. A similar process appears to operate in maintaining the required number of soldiers in the community.

III

Diet

Termites feed mainly on wood or other materials containing cellulose. The cellulose is partially digested by protozoans living symbiotically in the intestines of the worker (see Symbiosis). Enzymes produced by the protozoans break down the cellulose into components that can be assimilated by the termites. Digested cellulose is distributed by the workers to members lacking the protozoans. Some species feed on vegetable molds that they cultivate. Other species obtain a special fluid secreted by beetles, known as termitophiles, that live as guests within the termite community.

IV

Nests

Termite nests, called termitaries, vary widely. The nests of certain tropical species are huge moundlike structures, often 6 m (20 ft) in height. These mounds have extremely hard walls, constructed from bits of soil cemented with saliva and baked by the sun. Inside the walls are numerous chambers and galleries, interconnected by a complex network of passageways. Ventilation and drainage are provided, and heat required for hatching the eggs is obtained from the fermentation of organic matter, which is stored in the chambers serving as nurseries.

Of more than 55 species common in the United States, the majority build their nests underground. The subterranean termites are extremely destructive, because they tunnel their way to wooden structures, into which they burrow to obtain food. Given enough time, they will feed on the wood until nothing is left but a shell.

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