A review of the species groups of the Neotropical myrmecophilous genus Homopterus Westwood is presented based on the first molecular phylogenetic analysis of the genus and morphological study of 260 specimens. Two new species groups, the H. subcordatus group and the H. filiko group are erected based on the results of the molecular phylogenetic analysis and morphological analysis. The genus consists of one species known only from Dominican amber, H. hispanolienses Nagel, and thirteen extant species, one of which is described as new: Homopterus filiko n.sp. from Peru. An illustrated dichotomous identification key to species, diagnoses of the species groups and updated distribution maps are provided. The potential of several of the species groups to harbor additional cryptic diversity is discussed.