The fishing bat, Myotis vivesi, sometimes is placed in a separate genus or subgenus, Pizonyx Miller, 1906. M. lucifugus, a small North American species, usually weighs 5-14 grams. M. myotis, the largest species, weighs 18-45 grams. The upper parts are generally some shade of brown, and the underparts are paler.
Some forms have light and dark color phases.
M. formosus is remarkable for its orange coloration. M. vivesi is dark buff or pale tan above and whitish below. It differs from most Myotis in its greatly elongated feet and large, laterally compressed toes and hind claws. The tragus of Myotis is erect and tapering. This genus is the most widely distributed group of bats.