But unlike grasshoppers, locusts undergo a remarkable change when their populations grow. At high population densities, locusts may change body shape and size, and then band together into huge, highly mobile swarms that set off in search of food. The changes are so dramatic that researchers once believed that swarming and non-swarming locust forms were different species. For farmers, the arrival of a swarm can bring despair. In Africa, India, and Australia, swarms have eaten 20,000 tons of grain in a single day.
Locust swarms can bring farmers despair.
It covered several hundred square miles. Such swarms are so big that they are easily tracked by radar. Locust swarms also once threatened farmers in the western United States. But just when the farmers feared they would face starvation, flocks of gulls arrived, making a meal of the tasty insects. The settlers were so grateful to the bird, called the California Gull, that Utah eventually named it the state bird and erected a monument in its honor in a city square.