Aphidinea

a superfamily of herbivorous insects of the order Homoptera. The body length ranges from 0.5 mm to 6 mm. Winged aphids have two pairs of identical wings with a sparse network of veins. The mouth parts include a sharp stylet used for sucking. Development involves incomplete metamorphosis. The body coverings are thin, often with a downy or a waxy coating. Aphids feed on the juices of conifers and angiospermous plants and sometimes of ferns. The stings of many species may produce deformed proliferations of plant tissues (galls) or lead to twisting, thickening, wrinkling, and bending of the plant, as well as impeded growth. Many species of aphids select a specific plant species as host, and even a specific part of the plant.

The order is divided into 12 families, which include approximately 2,500 species. Aphids are distributed mainly in temperate latitudes. In the tropics and in high latitudes they are rarer and have less diversity of species. More than 800 species are known in the USSR. The insects live in dense or scattered colonies, producing as many as 20 generations a year.

The life cycle of aphids is often complex. The insects may be parthenogenetic, ovoviviparous, or viviparous. The roles of males and females change from generation to generation, and in some species males are rare or absent. Many species have alternating winged and wingless generations. Certain aphids migrate from one plant, the primary host, to another plant, the summer host, in a manner similar to the change of hosts in parasites. Such heteroecious aphids usually winter on the primary host, where the fertilized females deposit their eggs. In the spring the eggs yield wingless stem-mothers that give birth to winged offspring. The winged females, which are called spring migrants, fly over to the summer host, where a succession of parthenogenetic generations develops. The dioecious individuals of both sexes that are then born fly over to a plant of the same species as the primary host.

In some species of heteroecious aphids, the species of the primary host disappeared during the glacial period, and the insects were preserved only on the summer hosts. In the primary hosts, aphids mainly feed on the above-ground parts of the plants, while in the summer hosts they often also feed on the roots.

Many aphids are serious pests of cultivated plants, for example, the melon, pea, and cabbage aphids, plant lice (Phylloxeridae), rosy and wooly apple aphids, and the sugar beet root aphid, green peach aphid, snowball aphid, and English grain aphid. On the other hand, the galls formed by the insects on pistachio and sumac yield valuable dyes and tannins. A sugary liquid secreted by aphids and called honeydew is consumed as food by ants, which protect the aphids. There are myrmecophilous aphids that live in ants’ nests. The honeydew is also gathered by bees.