Their closest evolutionary relatives are the rodents , lagomorphs , insectivores , and primates . A bat's wing, called a patagium, is formed by a web of skin stretched between the body and the elongated second, fourth, and fifth fingers. Some bats may have an interfemoral patagium stretched between their legs and part or all of the tail this depends on the species. The interfemoral patagium is sometimes used as a net to catch insects in mid-flight. The chiropterans' niche is characterized mainly by their ability to fly and their use of echolocation.
Bats use echolocation by emitting pulses of very loud, high frequency sound.
When the sound bounces off an object and returns to the bat, it is processed into an image by the brain. Myotis lucifugus lucifugus, the little brown bat, is found in the eastern part of the United States. It belongs to the family Vespertilionidae whose range covers almost the entire planet. Vesper bats are almost all insectivores with the exception of a few carnivores. The foot size of M.l.lucifugus is 10 mm, and long toe hairs extend beyond the tips of the claws.