Structure in the aerial-feeding bat faunas of southeastern Ontario, southern British Columbia, Cameroun, Guyana, and the Philippines is demonstrated on the basis of wing shape and relative ear size. The former is derived from the ratio of the length of the third digit metacarpal to the length of the fifth digit metacarpal (III/V) and the latter from the ratio of the length of the ear to the length of the forearm (E/FA). It is assumed that these characters affect flight pattern and echolocatory characteristics and thus prey selection in the aerial-feeding, echolocating bat. On the basis of these characteristics some Emballonurinae and the Mormoopidae are thought to replace the Vespertilionidae in the neotropics, and some Phyllostomatinae may be neotropical counterparts of the Rhinolophidae, Nycteridae, and Megadermatidae. The Diclidurinae seem to parallel the old world Taphozous in wing shape and ear size.