Bats are the only mammals in the world that can fly. Their wings are extensions of the skin of their bellies and backs. The skin stretches between the fingers and the side of the body, and on many species it encloses the hind legs and tail. Bats vary greatly in size. The smallest, the bumble-bee bat, measures only 1 inch with a wingspan of 6 inches. The largest bat, the flying fox, has a body measuring 15 inches and a wingspan of 6 feet. The vampire bat of Latin America, which is the source for many fables and stories, consumes only blood. Most bats in North America only eat insects, up to 150 per hour. Many other bats will also eat nectar, fruit, blood and fish. While flying in the dark, bats are able to locate objects with echolocation, which is similar to sonar. They emit high-pitched sounds and listen for the echo that bounces back from the object.