from nat geo:
Locusts are related to grasshoppers and the two insects look similar. However, locust behavior can be something else entirely. Locusts are sometimes solitary insects with lifestyles much like grasshoppers. But locusts have another behavioral phase called the gregarious phase. When environmental conditions produce many green plants and promote breeding, locusts can congregate into thick, mobile, ravenous swarms.
from wiki:
Locust is the swarming phase of short-horned grasshoppers of the family Acrididae. The origin and apparent extinction of certain species of locust?some of which reached 6 inches (15 cm) in length?are unclear.[1]
These are species that can breed rapidly under suitable conditions and subsequently become gregarious and migratory. They form bands as nymphs and swarms as adults?both of which can travel great distances, rapidly stripping fields and greatly damaging crops.
photos of both look the same to me.
