Excerpt from page 3 - The Benefits of Bats
Bats are the primary predator of night-flying insects, from mosquitoes that spread disease (not to mention annoyance) to codling moths that attack apple trees and bollworm moths that feast on cotton plants. In fact, in some areas the moths that feed on farm crops make up 90 percent of a bat's diet; in others, the control of malaria has been aided by the resident bat population's diet of mosquitoes.
Big Brown Bats (that's the species' name, not just its description), which live primarily in agricultural areas, feed on June bugs, cucumber beetles, stinkbugs, corn rootworms, grasshoppers, and leafhoppers. Over the course of one summer, a colony of 150 Big Brown Bats will dispatch 38,000 cucumber beetles, 16,000 June bugs, 19,000 stinkbugs, and 50,000 leafhoppers while preventing 18 million corn rootworms from ever seeing the light of day by consuming the beetle stage of this insect pest. "Copyright permission by Storey Communications"