Curculionidae(redirected from Cossonus)
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generally known as weevils, a family of beetles that have heads extending into a rostrum at the end of which is found the gnawing mouth apparatus typical of beetles. In many weevils the rostrum is not only longer than the head but longer than the entire body. In weevils of the division Adelognatha the rostrum is usually no longer than the main part of the head, while in those of the division Phanerognatha it is much longer. The antennae are usually geniculate (exceptions include the seed weevils of the subfamily Apioninae). The tarsi are five-jointed, with the fourth joint being concealed in a notch of the third. The weevils of the division Adelognatha frequently have atrophied wings, and the wing cases (elytra) grow together over the abdomen, forming the fornix of the subelytral chamber, which protects the abdomen from drying out. Not infrequently the wing sheaths and other sclerotized outer parts bear outgrowths and spines, and many weevils have small scales, which give the body a metallic glitter. Most weevils are phytophagous, that is, they feed on various parts of living flowering plants; only a few, such as the species of the genus Cossonus, develop in rotting wood and as larvae feed on underground plant parts.
The weevils of the division Adelognatha usually lay their eggs in the ground, while most weevils of the division Phanerognatha lay their eggs in plant tissue, which serves as food for the larvae. The larvae are legless, C-shaped, and fleshy, with folding covers and well-developed head capsules. The body of the larva is usually white or cream colored, and the head is yellow or brown. Weevils are the most extensive family of organisms in terms of the number of species. About 40,000 species are known, of which as many as 4,000 are found among the fauna of the Soviet Union.
The larvae of Curculionidae weevils that develop in the soil are usually polyphagous, although some are oligophagous, such as the bean and pea weevil of the genus Sitona, which lives only in tubercles on the roots of legumes, and larvae of the beet pest Bothynoderes punctiventris, which live on the roots of some plants of the Chenopodiaceae family. Many species are strictly oligophagous, almost monophagous insects, adapted to feeding on specific plant species and parts of plants; frequently the species of weevil may be identified by the nature of the crop damage. The weevils of the genus Lixus develop in the stems of herbaceous dicotyledonous plants, those of the genus Pseudocleonus in the roots of plants of the Compositae family, and those of the genus Rhynchaenus in the parenchyma of leaves. The species Ceuthorrhynchus punctiger develops in the calathides of dandelions, the species C. macula-alba in the pods of poppies, and species of the genus Apion in the heads of clover. Only rarely do the larvae develop openly on plant leaves; in such cases they resemble green caterpillars with fixative tubercles on the abdominal and thoracic segments, for example, the species Phytonomus variabilis. Pupatation takes place in the soil or in the tissues of the nourishing plant. The larvae that feed openly on leaves also pupate there, after spinning a gossamer cocoon (for example, the species of the genus Phytonomus} or a cocoon of hardened secreted mucus (the species of the genus Cionus).
Among the weevils are many pests that damage agricultural plants, and these must be continuously combated. They include the beet weevil, the clover-leaf weevil, the cotton weevil (Anthonomus grandis), and the apple-blossom weevil (A. pomorum). Weevils of the family Curculionidae are similar to the leaf rollers of the Attelabidae family.
REFERENCESZhizn’ zhivotnykh, vol. 3. Edited by L. A. Zenkevich. Moscow, 1969.
Opredelitel’ nasekomykh Evropeiskoi chasti SSSR, vol. 2. Edited by G. Ia. Bei-Bienko. Moscow-Leningrad, 1965.
Bei-Bienko, G. Ia. Obshchaia entomologiia. Moscow, 1966.
M. S. GILIAROV