The velvety free-tailed bat is found nowhere in the United States but extreme south Florida. These bats emerge from their roosts earlier than most other bats, often shortly before sunset. This 2-page fact sheet written by Holly K. Ober, Terry Doonan, and Emily Evans, and published by the UF Department of Wildlife Ecology and Conservation explains how to differentiate velvety free-tailed bats from Brazilian free-tailed bats and Florida bonneted bats.
http://edis.ifas.ufl.edu/uw425