Still a major threat? In Africa,the last serious widespread plague of Locusta m.migratorioides occurred from 1928 to 1942.Since then, environmental transformations have made the development of swarms from the migratory locust unlikely.However,the desert locust which is very similar to the African migratory locust remains a major threat.Still a major threat? Still a major threat? In Africa, the last serious widespread plague of Locusta m. migratorioides occurred from 1928 to 1942. Since then, environmental transformations have made the development of swarms from the migratory locust unlikely. However, the desert locust which is very similar to the African migratory locust remains a major threat