The most destructive insect is the desert locust (Schistocera gregaria), the locust described in the Bible. This insect's habitat ranges from the dry and semi-dry regions of Africa and the Middle East, through Pakistan and northern India. This short-horn grasshopper can eat its own weight in food in one day. During long migratory flights, a large swarm can consume 20,000 tons (18,144,000 kilograms) of grain and vegetation per day.
Source: Wood, Gerald L. The Guinness Book of Animal Facts and Feats, 3rd ed., p. 174.