Locust migration is an occasional event, which follows an enormous buildup of a locust population. The young locusts, called nymphs, only develop into the migratory form under certain environmental conditions, which also lead to a population increase. Not all of the environmental factors involved are known, but one is hot weather. The first generation produced after a migration is not usually migratory.
When migration occurs the locust swarms are so dense as to blacken the sky over an area of many miles. When the insects finally settle, after traveling hundreds or thousands of miles, they begin to feed, consuming enormous quantities of vegetation. Locusts are serious agricultural pests. Spraying with solutions of arsenic and overturning the soil can destroy the eggs.
Locusts are most common in Africa and Asia, but also occur in the United States. The Rocky Mountain locust, Melanopolus spretus, a species that is now apparently extinct, destroyed millions of dollars worth of crops on the Great Plains between 1874 and 1877. A single swarm contained an estimated 124 billion insects. Cicadas are sometimes called locusts in the United States but are related to aphids and leafhoppers, not grasshoppers.
Locusts are classified in the phylum Arthropoda, class Insecta, order Orthoptera, suborder Caelifera, family Acrididae.
The Columbia Electronic Encyclopedia, 6th ed. Copyright © 2012, Columbia University Press. All rights reserved.
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