Locusts are members of the grasshopper family. Locusts differ from grasshoppers because they have the ability to change their behaviour and physiology, in particular their morphology (colour and shape), in response to changes in density, when meteorological conditions are favourable. Adult locusts can form swarms that may contain millions or billions of individuals that behave as a coherent unit.

Desert Locusts are always present somewhere in the deserts between Mauritania and India. When numbers are low, they behave as individuals (solitarious phase); when high, they behave as a single mass (gregarious phase).