locust

Locusts

What are locusts?

Locusts are insects belonging to the order Orthoptera. They are identical in appearance to grasshoppers with which they share the family Acrididae. The only difference between the two types of insects is that locusts can exist in two different behavioral states (solitary and gregarious) whereas grasshoppers do not. When the population density is low locusts behave as individuals, much like grasshoppers. However, when the population density is high locusts form highly mobile gregariously behaving bands of nymphs or swarms of adults. It is this change from one behavioral state to another, known as phase change that makes locusts such devastating pests. Phase change may be accompanied by changes in body shape and color, and in fertility, survival and migratory behavior. These changes are so dramatic in many species that the swarming and non-swarming forms were once considered to be different species.

Shorthorned grasshoppers, also known as true grasshoppers, are named for their relatively short antennae. A common species, the American grasshopper, is about 4 inches long when fully grown. In the fall, females lay their eggs in holes in the ground. The eggs hatch in the spring, and the young reach maturity in July or August. When some shorthorned grasshoppers reproduce too rapidly for their food supply to support them, subsequent generations undergo extensive changes in form and become migratory. Such shorthorned grasshoppers are known as locusts.

The true locust is one of over 5000 species of grasshopper. Locusts travel in huge numbers capable of feeding on and destroying entire fields of cultivated plants and any nearby vegetation. Approaching swarms create an ominous hum and sometimes are large enough to block out sunlight.

Locust is the common name applied to a number of jumping insects and especially to the true locusts, which are migratory grasshoppers. The true locusts cause great damage to crops wherever they swarm. Control measures include the spreading of poison bait and the plowing under of locust eggs. Infestations threatening large regions of the United States are combated with insecticides sprayed by planes and truck-mounted mist blowers provided by joint federal-state programs.

Grasshopper is the common name for any of the winged orthopteran insects with hind legs adapted for jumping. They include the longhorned grasshoppers, pygmy grasshoppers, and shorthorned grasshoppers, or locusts. They subsist on vegetation and are distributed worldwide wherever vegetation grows.

Grasshoppers are 1 to 5 inches long when fully grown. They develop by gradual metamorphosis: The nymph is initially wingless and gradually comes to resemble the adult as it grows through progressive molts. Only the adults can fly. Some species undergo seasonal color changes, being green at some times and red or brown at others. Grasshoppers are closely related to crickets and male grasshoppers make chirping or stridulating noises similar to those produced by crickets. Females of several species also make sounds. Unlike true crickets and longhorned grasshoppers, shorthorned grasshoppers chirp by rubbing their hind legs or forewings against other parts of their bodies. The eardrums of shorthorned grasshoppers are clear, circular areas located on the abdomen at a point just behind the junction of the hind legs with the body. The hearing organs of longhorned grasshoppers and crickets are located on the forelegs.

Pygmy grasshoppers are the smallest grasshoppers and are characterized by a greatly elongated dorsal shield, a backward extension of the thorax. Longhorned grasshoppers are characterized by antennae that extend beyond the hind end of the body when they are folded back. Females usually lay their eggs in low bushes or in crevices in the bark of trees. Longhorned grasshoppers include the katydids (see Katydid); the meadow grasshoppers, which are slightly less than 1 inch long; and the so-called Mormon cricket found in the western United States, which was common near the early Mormon settlement in Salt Lake City, Utah, and did much damage to crops there.

Life cycle of a locust

Locusts pass through three main stages of development: egg, nymph (hopper) and adult.

Locust eggs are laid in the soil. The female drills a hole into the ground using her ovipositor and lays a 'pod' of eggs which is sealed with froth. Locusts hatch from eggs as wingless nymphs.

Rainfall, which produces green vegetation, is necessary for nymphal and adult survival, adult migration and/or egg development. Egg laying usually follows either migration or rainfall.

How long it takes for a locust to reach maturity depends on the species, conditions of the habitat and on temperature. In cool weather, nymphs and adults often attempt to increase their body temperature by basking in the sun.

Orthoptera

Large order of insects including the grasshoppers, locusts; katydids; and crickets

The insects in this order have mouthparts fitted for biting, and they are characterized by incomplete metamorphosis. The young, when first hatched, closely resemble the adult insects except in size and the absence of wings. The eggs are comparatively few in number and as a rule are laid in specialized egg cases, although some orthopterans deposit or scatter eggs without such cases. About 23,000 species are known; many swarm in enormous numbers, as in the case of the destructive migratory locusts. The ability to produce sounds of distinct tones and rhythms by rubbing one part of the body upon another is highly developed. Only the males of families that jump have this ability in order to attract females. In the tropical forms, the wings seem to be of little use as organs of flight, but they are of striking value in ornamentation and in concealment.