Locusts

species of gregarious Acridoidea (grasshoppers) distributed in Southern Europe, South Asia, East Asia, Africa, South America, North America, and Australia. In periods of mass reproduction, swarms of larvae or adult individuals are formed. With a high concentration of locusts the gregarious phase is usual; with a low concentration the insects are solitary. The larvae of the Asiatic locust (Locusta migratoria migratoria) have protective body coloration, usually green, in the solitary phase. Larvae in the gregarious phase are black and orange.

Locusts are extremely dangerous pests of agricultural crops (cereal grains, cotton) owing to the possibility of unexpected influxes from distant lands and mass attacks on plantings. Traveling more than 30 km in the course of a day in search of food, the swarms destroy all green vegetation in their path. The larvae and the adult individuals alike feed on leaves, stems, panicles, spikes, fruits, and stem bark. Sometimes trees and shrubs break under the weight of locust swarms. A locust eats about 300 g of green plant matter in its lifetime. Larvae feed 20 to 30 times a day; adult locusts in swarms feed somewhat less frequently owing to migratory flights. The amount of food eaten by an adult locust during prolonged flights is noticeably larger than the amount consumed on short migrations. During periods of mass reproduction, the number of individuals per sq m reaches several hundred or thousand, and the area settled by the locusts often comprises nearly 1 million hectares. The damage caused by locusts to crops and wild plants is often disastrous.

In the USSR the most destructive locusts are the Asiatic locust, the Middle Russian locust (Locusta migratoria rossica), the Italian locust (Calliptamus italicus), the Moroccan locust (Dociostaurus maroccanus), Calliptamus turanicus, and the desert locust (Schistoceria gregaria) from Iran and Afghanistan.

The migratory locust (Locusta migratoria) is found in Europe, Asia, Africa, and northern Australia, as well as on several islands in the Indian and Pacific oceans. It has a number of subspecies, including the Middle Russian locust, the Asiatic locust, the African locust (L. migratoria migratorioides), and the eastern locust (L. migratoria manilensis). The migratory locust is injurious to almost all crops but prefers cereals.

The Middle Russian locust inhabits the forest and forest-steppe zones of the European USSR. It resembles the Asiatic locust, but the colder climate of its habitat causes differences in breeding period, life-span, and other characteristics.

The Moroccan locust is a large insect, reaching a length of 20–28 mm in males and 28–38 mm in females. It is reddish yellow with dark spots; the hind legs are red or yellow with a light base. The Moroccan locust is distributed in Southern Europe, North Africa, and Western Asia. In the USSR it is encountered in the European part (including the Caucasus), Middle Asia, and southern Kazakhstan. The locust is particularly injurious to cereals, cotton, alfalfa, clover, vegetables, and cucurbitaceous crops. The larvae usually devour crops completely, whereas the adult locust generally only gnaws through the bases of the stems.

Calliptamus turanicus is distributed in Northern China, Afghanistan, southern parts of Kazakhstan, and some regions of Middle Asia. The males are 12.9–21 mm long, and the females 25–32.5 mm. The insects do extensive damage to dry-farming plantings of grains, cotton, and some nectar-bearers.

Control measures against locusts include the use of poisoned baits, dusting or spraying with insecticides (aerial dusting for large infested areas), plowing vacant lands and wastelands (foci of locusts), draining flooded areas and using them for crop cultivation, the use of pasture rotation, and restoring grass cover (harrowing, planting grass, snow retention). Other measures include planting crops that locusts do not feed on in areas of mass reproduction, drying reed thickets in river deltas in desert and semidesert zones, and flooding a number of hay meadows to enrich the plant cover in the steppe zone. These control measures have eliminated many large nidi of Moroccan and Italian locusts in the Northern Caucasus and have suppressed sources of the Asiatic locust in the southern European part of the RSFSR and in some regions of Middle Asia and Kazakhstan.