In many parts of the U.S., what we call “locusts” are actually cicadas—that plug-shaped insect that sings in the trees.

But especially in Africa and the Middle East, “locusts” are large grasshoppers occurring in massive swarms that can devour crops across the region.

These grasshoppers have undergone a strange metamorphosis.

In normal times, they’re a shy, solitary desert hopper. Heat and drought control their numbers, and they’re not a threat to agriculture.

But every few decades—when heavy rains span several seasons—vastly more eggs hatch, and the population explodes.

So many insects in close contact causes serotonin to flood their brains, and profound changes occur.

The juveniles band together in nomadic hordes, crawling across the landscape looking for food. They grow larger than normal, faster, and even change color.

Adults grow larger wings and jaws and take to the sky, forming swarms of billions, devastating the vegetation in their path. These swarms can span a thousand square miles and fly 80 miles in a day.

Aerial pesticide spraying can reduce their numbers but has problems of its own: contaminating crops and water.

The insects are edible and considered a delicacy, and make excellent cattle fodder. But there are so many that eating them makes little difference.

Eventually, dry conditions return and the swarms die. The eggs that hatch will again become the peaceful desert grasshopper… until the next unusually wet spell.