Among 1,000 species of bats, only 3 feed on blood. This stereotypical image is based on vampire stories. Bats are often said to be blind, such as in the expression "as blind as a bat," when in reality bats are not blind, but Microbats have poor visual acuity. In contrast, some Megabats have very good vision.

Although the eyes of most microbat species are small and poorly developed, leading to poor visual acuity, no species is blind. Microbats use vision to navigate, especially for long distances when beyond the range of echolocation. Some species have been shown to be able to detect ultraviolet light.

The United States is home to an estimated 45 to 48 species of bats. The three most common species are Myotis lucifugus (little brown bat), Eptesicus fuscus (big brown bat), and Tadarida brasiliensis (Mexican free-tailed bat). The little and the big brown bats are common throughout the northern two-thirds of the country, while the Mexican free-tailed bat is the most common species in the southwest.

Bats are usually classified into two main groups: Microchiroptera (the most numerous, and commonly found throughout the world), and Megachiroptera (fruit bats, found in Asia, Africa and Australasia). With one exception, Megabats do not echolocate, and rely on a developed sense of vision to navigate. The visual receptive fields of neurons in the superior colliculus in these animals form a precise map of the retina, similar to that found in cats and primates.