scale insect, common name for members of a highly modified group of insects belonging to several families of the superfamily Coccoidea. Scales possess antennae and are characterized by reduced legs. Only the males have wings; females are always wingless. Scales are popularly subdivided into three groups; the armored scales, the unarmored scales, and the mealybugs mealybug, common name for certain unarmored scale insects that exude a granular white secretion, giving them a mealy appearance. Many are common greenhouse and crop pests. Adult females are wingless, with oval, segmented bodies and well-developed legs.
..... Click the link for more information. . The armored scales secrete a wax covering, the shape of which is characteristic for any given species. Under this coat, the insects develop and feed, sucking the sap of plants with their thin tubular mouthparts. The females never leave the protection of the scale after once forming it, but the adult males, which do not feed, develop a single pair of wings, leave the scale, and seek out the females, fertilizing them after the females are under the shell. Among the important armored scale pests of citrus, other fruits, and ornamentals are the San Jose scale San Jose scale, common name for a scale insect , Aspidiotus perniciosus, introduced from China into San Jose, Calif., c.1870 on nursery stock. The insect has since spread throughout much of the United States and Canada.
..... Click the link for more information. , the oyster scale, the purple scale, and the California and Florida red scales. The unarmored scales (or soft scales) are similar to the armored scales except that only a small amount of wax is secreted, which adheres to the insect. Unarmored scale pests of citrus fruits include the black scale and citricola scale. Mealybugs appear as white cottony clusters on citrus, ornamentals, and greenhouse plants. Like other scale insects, newly hatched nymphs, called crawlers, have legs and actively seek out food. When they find a suitable spot, they settle down to feed. Some scales secrete a resinous covering, which is used in the commercial production of shellac, varnish, and paints (see lac lac, resinous exudation from the bodies of females of a species of scale insect (Tachardia lacca), from which shellac is prepared. India is the chief source of shellac, although some is obtained from other areas in Southeast Asia.
..... Click the link for more information. ). Control of scale insects has been largely by use of natural enemies, especially ladybird beetles and small parasitic wasps, which are natural predators of these pests. Scale insects have proved difficult to control by chemical means. Scale insects are classified in the phylum Arthropoda Arthropoda (ärthrŏp`ədə) [Gr.,=jointed feet], largest and most diverse animal phylum.
..... Click the link for more information. , class Insecta, order Homoptera, superfamily Coccoidea.

scale insect

Any member of several families of sap-sucking insects (order Homoptera) whose bodies are covered by a waxy shell (the scale). The eggs are protected by the female's body or scale or a waxy filamentous mass. Scale insects may attack any part of a plant, but each species is host-specific. Many species are serious plant pests; others have commercial value. The lac insect is used in a red dye and in shellac. Cochineal, a red dyestuff, consists of the dried, pulverized bodies of females of the species Dactylopius coccus. See also cottony-cushion scale, San Jose scale.