Visualize a swarm of 70 billion flying insects, covering 460 square miles—about 1.5 times the size of New York City—and devouring more than 300 million pounds of crops in one day. That’s how big a single swarm can get. Plagues, made up of multiple swarms, are referenced in the Bible and the Quran. Of the thousands of grasshopper species, only 22 can be described as locusts. They’re distinguished by their ability to transform from a solitary state—actively avoiding other locusts—into a social, or “gregarious,” state in which masses of them darken the sky, ravage the land, and terrorize inhabitants.