They differ from all other mammals, however, in their ability to fly. Their wings are folds of skin stretched between elongated finger bones, the sides of the body, the hind limbs, and, in Canadian species, the tail. A resting bat usually hangs head downward and takes flight by releasing its toehold. Flying bats appear larger than resting bats because of their large wing area. The smallest Canadian species, the Small-footed Bat Myotis leibii weighs 5g.
Bats are primarily nocturnal creatures, sleeping during the day and hunting and feeding at night.
Although some bats in the Tropics feed on fish, fruit, nectar, or even blood, the bats of Canada feed on insects, usually caught in flight. Bats will take moths, mosquitoes, beetles, mayflies, caddis flies, and midges. In the stomach of one Little Brown Bat 145 mosquitoes were found. Birds that pursue flying insects often catch their prey in their mouths, but most insectivorous bats scoop up their victims in wing or tail membranes before transferring them to the mouth. Little Brown Bats can chew their food very rapidly and in the laboratory have been observed catching mosquitoes at a rate of 10 per minute.