Isoptera

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Isoptera

[ī′säp·tə·rə]
(invertebrate zoology)
An order of Insecta containing morphologically primitive forms characterized by gradual metamorphosis, lack of true larval and pupal stages, biting and prognathous mouthparts, two pairs of subequal wings, and the abdomen joined broadly to the thorax.

Isoptera

 

(termites), an order of insects, closely related to the Blattoidea (cockroaches) and Mantodea (mantises), characterized by incomplete (gradual) metamorphosis and a social organization that shows a marked diversity of individuals within a species (sexual and caste polymorphism).

Isoptera live in nests in colonies of several hundred to several million individuals. The colony consists of a female and a male (the royal pair) or the neoteinic reproductives that replace them and of large and small soldiers and workers—males and females with reduced reproductive glands. In lower Isoptera, true workers are replaced by nymphs. Some Isoptera have no soldier caste. The workers are 2–15 mm in length, and the soldiers up to 20 mm; egg-laying females with hypertrophied ovaries reach 140 mm in length. Adult reproductives have two pairs of elongated, delicate, membranous wings, which they shed after flight, and compound eyes. In other castes, the eyes are underdeveloped or absent. Symbiotic protozoans—flagellates of the order Hyper-mastigina—develop in the intestines of Isoptera; they enable Isoptera to digest the cellulose that represents the principal source of food for the majority of species. Some Isoptera feed only on fungi, chiefly molds, which they raise in fungus gardens.

A colony centers on the royal pair. After rearing the first workers, the female is periodically refertilized by the male and thereafter only lays eggs. The life-span of the royal pair ranges to several decades; the colony, however, may exist for many decades. Workers provide the colony with food and build the nest and galleries. Isoptera in a single colony constantly exchange food (tro-phallaxis). The development of castes in Isoptera is associated with the division into reproductive and sterile individuals, as well as into workers and soldiers. The insects’ way of life is usually hidden from man. The nests are diverse in shape and size; some tropical species build nests 15 m high. Several species have subterranean nests; others eat out the interior of wood. Isoptera actively regulate the microclimate of the nest. Many invertebrates (termitophiles) are symbionts of Isoptera in the nests; they include coleóptera, oniscoideans, myriapods, and acarians.

There are approximately 2,600 species of Isoptera, grouped in six families. They are chiefly distributed in the tropics and partly in the subtropics. There are seven species in four families in the USSR—in the southwestern Ukrainian SSR, on the coast of the Black Sea in the Caucasus, in Middle Asia, and in the Far East. Isoptera destroy wood and other materials; in Africa and India they damage crops. There is a constant struggle to control harmful Isoptera.

REFERENCES

Luppova, A. N. “Termity Turkmenistana.” Tr. ln-ta zoologii i parazitologii (AN Turkm. SSR), 1958, issue 2.
Zhizri zhivotnykh, vol. 3. Moscow, 1969. Pages 204–10.
Grassé, P. P. “Ordre des isoptères au termites.” In Traité de zoologie, vol. 9. Paris, 1949.
Goetsch, W. Vergleichende Biologie der Insecten-Staaten. Leipzig, 1953.
Harris, W. Termites, Their Recognition and Control. London, 1961.

A. A. ZAKHAROV