what corp- ravagomg swarms can contain 10 billion individuals and cover 400 square miles?

Locusts (I assume you meant "crop-ravaging" although I kind of liked your translation)

Locust is the call given to the swarming part of short-horned grasshoppers of the kin Acrididae. The origins and glaring extinction of particular species of locust—a number of which attain 6 inches (15 cm) in length—are uncertain. those are species that may breed right now lower than ideal circumstances and hence grow to be gregarious and migratory. They type bands as nymphs and swarms as adults- both one in all that may go back and forth large distances, right now stripping fields and very much negative vegetation.