Arthropods are the primary dietary constituents of species of the genus Myotis. The genus comprises 3 ecomorphotypes of polyphyletic origin, each associated with a different foraging strategy: aerial, trawling, and gleaning, related to the subgenera Selysius, Leuconoe, and Myotis, respectively. We explored the extent to which differences in diet characterized these ecomorphotypes. Based on a broad review of the literature, we classified the diet of species of Myotis based on hardness and vagility of consumed prey. A significant negative relationship was found between the percent volume consumption of hard and soft arthropods and between the aerodynamic characteristics of fast- and slow-flying prey. A cluster analysis yielded 3 groups of Myotis species based on their diet: 1) those for which hard prey represent more than 80% of the volume of excreta; 2) those for which hard prey represent 45% to 80% of the volume of excreta; and 3) those for which hard prey represent less than 45% of the volume of excreta. These 3 groups are related to bat size and consistent with the recognition of 3 ecomorphotypes. Nonetheless, some species may display flexibility in diet composition depending on food availability. More specifically, larger species that consume hard prey also consume soft prey, whereas smaller bats may be unable to consume hard prey because of biomechanical limitations. Regardless of their phylogenetic lineages, latitudinal distribution, or biogeographic affinity, species of Myotis of similar size and morphology consume arthropods with similar characteristics.