Wingspan: 11–12.5 in.
Length: 3–4 in.
Weight: 0.43–0.49 oz
Color: Medium-sized with brown or black fur on its back and paler fur on the underside.
Other: Ears are short and pointed; eyes are small. Is recognized by its erratic flight.
Roosting behavior: Forms maternity colonies, usually numbering in the thousands in caves, mines, barns, and buildings and sometimes under bridges.