termite
termite or white ant, common name for a soft-bodied social insect of the order Isoptera. Termites are easily distinguished from ants by comparison of the base of the abdomen, which is broadly joined to the thorax in termites; in ants, there is only a slender connection (petiole) joining these segments. In addition, the antennae of termites are beadlike or threadlike, while ant antennae are elbowed. Termites have chewing mouthparts. They feed chiefly on wood, from which they obtain cellulose. In primitive species cellulose is converted into various sugars by specialized gut protozoans and in the more highly evolved termites by specialized bacteria living symbiotically in the termite's digestive tract. Termites undergo gradual metamorphosis (see insect ). The nearly 2,000 species are mostly tropical, and some build huge mounds to house their colonies. These mounds, up to 40 ft (12.2 m) high, are a characteristic feature of the landscape in parts of Africa and Australia.
Termite Colonies and Castes
Termite colonies are composed of three castes; the reproductives (kings and queens), the soldiers, and the workers. The kings and queens are sexually mature termites, with compound eyes and fully developed wings. The workers and soldiers lack wings and compound eyes. Sexually mature termites, or reproductives, are produced in large numbers during certain seasons and leave the colony in a swarm. They are poor fliers, and most are eaten by birds and other animals.
When the surviving termites settle, their wings break off along a weakened seam at the base. They then form pairs, each of which establishes a new colony. A couple excavates a chamber in wood or soil, in which they mate; they remain permanently paired, and the queen eventually produces as many as 30,000 eggs per day. Two or three weeks after mating, the young nymphs hatch and are fed on liquid secreted by the parents and on fecal wastes, from which they obtain the protozoan or bacterial symbionts essential for life.
The caste into which the young termite, or nymph, develops is dependent upon the amount of growth-inhibiting substance (a pheromone) passed to it during feeding and grooming. The pheromone is secreted by the reproductives and, when present in a high enough concentration, prevents the development of nymphs into reproductives. (A large colony may have several pairs of reproductives.) As more workers and soldiers are added, since they do not produce the pheromone, its concentration in the colony is correspondingly decreased. Therefore when the colony reaches a certain size, some of the nymphs begin to develop into reproductives, which then produce pheromones. This phenomenon also occurs if the original reproductives die. The increase in the pheromone level prevents the maturation of additional nymphs into reproductives; these remaining nymphs then become workers. In a similar way, the appearance of soldiers appears to inhibit the production of more soldiers.
In some families of termites, no workers develop, and the nymphs perform worker functions, which include feeding the royal couple, the soldiers, and the very young nymphs; caring for the eggs; grooming the queen; constructing and repairing the nest; and foraging for food. The soldiers have heads as large as the rest of the body and equipped with strong mandibles used in defense of the colony. They attack any intruders to the colony and stand guard at the entrances, in some species closing the entrances by putting their heads in the holes. Soldiers of certain species squirt a sticky, poisonous secretion at enemies.
Damage by Termites
There are two major groups of termites, the wood dwellers (family Hodotermitidae) and the soil dwellers (family Rhinotermitidae). The latter cause over $250 million loss per year in the United States alone. The Formosan termite, a more aggressive species than the U.S. species, was discovered in the United States in 1965 along the Gulf and in Atlantic port cities. Soil dwellers attack only wood that is in contact with the ground or close enough to be reached through enclosed earthen runways, which are connected to the termite's underground galleries. Treatment of soil, use of treated wood, or shielding with metal and concrete are among the methods used to prevent entry of termites into buildings. Drywood termites do not require as high a humidity as do soil dwellers and will attack trees, fence posts, stumps, and wooden buildings.
Classification
Termites are classified in the phylum Arthropoda , class Insecta, order Isoptera.
Bibliography
For information on prevention and control of termites, see publications of the U.S. Dept. of Agriculture or State Extension Service.
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