Wikijunior:Bugs/Locust

What does it look like?
Locusts belong to the order Orthoptera. They make up several species of short-horned grasshoppers belonging to the family Acrididae. They are grasshoppers in their “solitary” form and locusts in their swarming or “gregarious” form.

They have six legs. The first 2 pair are walking legs. The hind legs are longer than the others and modified for jumping. The segment of the leg closest to the body is called the femur. It has powerful muscles that move lower parts of the leg.

Locusts have 2 pair of wings that overlap the abdomen when they are at rest. They have large compound eyes. Their antennae are jointed and are various lengths depending on the species.

Carolina Locusts are cinnamon-brown to grayish-tan in color. Their hind wings are black with a pale yellow border. The pronotum, just behind the head, has a high, narrow middle ridge. They are 1-3/8 to 2 inches long. In flight, they make a very fast purring sound, followed by a fluttering sound.

Long-winged Locusts are related to Carolina locusts. They are brownish-yellow in color with brown-spotted forewings. Their black hindwings have a narrow yellow border. They are usually 1-3/8 to 1-3/4 inches long.

American Desert Locusts (Schistocerca americana) are a genus of grasshopper, many of which swarm as locusts. They are commonly called bird grasshoppers. The best known species is probably the Desert Locust (Schistocerca gregaris). Desesrt Locusts (Schistocerca gregaria) can be as long as 3 inches in length. The male and female look very much alike with a small difference. Males have a boat-shaped tip on the abdomen. Females have two valves on the tip of the abdomen that are used when they deposit eggs. Red-legged Locusts (Melanoplus femur-rubrum) are about 3/4 to 1-inch in length. They can be dark brown to greenish-yellow or red-brown. The hind femora have either a herringbone pattern or black spots. The hind tibiae are bright red to yellowish with black spines.

Australian Plague Locusts (Chortoicetes terminifera) vary in color from brown to green. The middle section of the body between the head and the abdomen (thorax) has an 'X' shaped mark. The wings are clear with a dark spot on the end of each wing.

Where does it live?
Desert Locusts are able to migrate very widely and are well known around the world. They are found in North Africa, the Middle East, and the Indian subcontinent.

Carolina Locusts are found throughout North America, some have been found that are green in color. They live along roadsides and dry fields. Long-winged Locusts are found from southwest Kansas to Texas, west to New Mexico, and north to Idaho.

Red-legged Locusts are found on the Atlantic Coast south to Florida, west to Arizona, and north to Alberta, Canada. Their habitats are vacant lots in urban and suburban areas, fields, and open woods. They live along irrigation ditches in arid areas.

The Migratory Locust is the most widespread locust species. It lives throughout Africa, Asia, Australia and New Zealand. It was once common in Europe but but is now rarely seen.

What does it eat?
Carolina Locusts eat grasses and other plants, and sometimes beans. Long-winged Locusts eat and destroy grasses that grow in plains. Red-legged Locusts consume grasses, weeds, and crops in the Southwest and soybeans in the Midwest.

How does it defend itself?
Locusts avoid predators by jumping away on strong legs. They raise the front part of the body on the walking legs and flex the joints between the femora and the tibiae. The tibiae of both walking legs suddenly extend, the legs straighten and push against the ground to propel the grasshopper into the air. When frightened by a predator, a large locust can cover about fifteen times the length of its own body.

Locusts use camouflage to blend into the surroundings. The coloring of different species often depends on the environment. Greenish colored species living in fields and forests can hide in green vegetation. Brown or tan colored species live in dry, sandy areas and easily blend with the colors of sand and dry dirt.

What stages of metamorphosis does it go through?
Locusts undergo incomplete metamorphosis. Females lay eggs in the ground or on plants. There are three distinct, gradual stages of development—egg, nymph and adult. There is no pupal stage. When eggs hatch the nymphs called “hoppers” appear. They usually resemble the adult but have no wings and are not able to reproduce. In the adult stage, they live 3 to 5 months.

The female Carolina Locust deposits 20 to 70 eggs in soft soil. Nymphs are speckled so they blend in with the ground, safe from predators.

The eggs of the Red-legged Locust spend the winter in soft soil. In the South where weather is warm, nymphs appear in spring. By June, they are mature adults. They mature later in the summer in the cooler North.

Australian Plague Locusts usually mature and lay eggs within five to seven days after a rain event. Females make a hole in the soil and deposit 2 to 3 pods. Each pod contains 30 to 50 eggs. Eggs usually take around two weeks to develop. Nymphs become adults in 20 to 25 days. Brown locusts have a drought-resistant egg stage and a short life cycle with 2 to 4 generations per year. Eggs are usually laid in dry soil. In the summer months eggs hatch about 10 days after a rainfall.

What special behavior does it exhibit?
A locust walks with 6 legs, using an alternating “tripod” gait. The front and rear legs of one side of the body form a tripod with the middle leg of the opposite side. The 2 tripods alternate with each other as the locust walks. This kind of walking provides more stability than a 2-legged gait or a 4-legged gait.

When overcrowding occurs in some grasshopper species, phase transformation takes place in each individual. There is a change from individual form to swarming form. This is a rapid and reversible change. The head widens, the body grows larger, and wings grow longer until the grasshopper has turned into a locust. Reproduction starts earlier and adults mature sooner. The differences between grasshoppers and locusts are so great that they were once thought to be two different species.

High population densities result from higher than average rainy seasons with dry periods in between. When too dry, habitats shrink and food becomes limited. Contact between individual locusts increases. When there are too many locusts in an area, “critical density” is reached and they take to the air in great numbers.

Experts used to think locusts swarmed to migrate from one place to another. Now it is believed they swarm to look for food. When locusts swarm, there can be as many as 150 million in one square mile. An adult locust can consume its own weight in food each day. A million locusts can devour one ton of food.

How does this bug affect people?
The Australian Plague Locust is the most damaging locust species in Australia. It has a very large range and swarms often. This species mainly attacks pastures but sometimes damages crops.

Desert Locusts are well known since Bible times as being the 8th plague sent by God against the Egyptians. Both male and female Red-legged Locusts transmit poultry tapeworms. They also transmit parasites that harm quail, turkeys, and guinea fowl.