As soon as he hears it, the bat knows what is in front of him. If it is a tree, he flies around it. Then he bites the insect with his sharp teeth. All this happens while he's flying, and that's why bats look like they're doing acrobatics in the air. Fancy flying is a bat specialty.
Most bats do eat insects, but some eat tiny fish, fruit, or pollen and nectar.
Everyone has heard of the vampire bat. And they DON'T suck blood. Then they just lick up a little blood. Doctors think we might be able to use bat spit to keep blood from coagulating during dangerous heart operations. Some bats live together in big colonies during the winter.