In the Bible, we read of plagues of locusts descending upon a people and causing great suffering. Of course, in those times such a plague was considered a punishment from God, just as floods, Rousts and disease.

But plagues of locusts have appeared in other times and in other lands, too. In the western United States, there was such a plague from 1874 to 1876 that did more than $200,000,000 worth of damage!

The word “locust” has been applied to many members of the grasshopper family. A locust is actually any of a group of insects that belong to a family called “Acrididae.” The so-called 17-year locust is not really a locust but a cicada.

Many scientists have been studying the question of why these insects descend on a region in great swarms at certain times, and seem to disappear between those times.

It seems that the species of locust that produces the “plague” exists in two phases, or periods. The two phases are solitary and gregarious, or in groups. In these two extreme phases, the locusts are quite different. They differ in color, form, structure, and behavior.

In the solitary phase, the locusts do not congregate and are sluggish in behavior. Their color matches that of their surroundings. In the gregarious phase, the locusts have a black and yellow color, congregate in great groups, are very active and nervous, and they even have a higher temperature. There are other differences as well. The solitary phase is the normal phase for the locusts.

When, for some reason, crowding is forced on the locusts in the solitary phase, they produce locusts of the gregarious type. These locusts are restless and irritable; they begin to wander; they are joined by others; a great swarm develops, and soon millions of them are rev to descend on a region in the form of a plague!