Species of Formica

ABSTRACT We revise the Nearctic endemic Formica pallidefulva group based on study of types and other museum specimens and material in J. Trager's collection. The latter material originates from 30 years of accumulated samples, both from free-living colonies of F. pallidefulva group species, and from "slave" populations in colonies of Polyergus lucidus s. l., which have single-species host populations. Among the currently available names for the group, the four valid taxa are F. archboldi, F. dolosa, F. incerta and F. pallidefulva. There is a fifth common, but previously unrecognized new species, described here as Formica biophilica Trager, n. sp. Earlier taxonomies of this group were constrained by typological thinking and inadequate treatment of metric characters. For this study, well preserved individuals, nest series and types of all but one taxon were studied (no types seen for F. pallidefulva). Analysis focused on form, length, abundance and distribution of macrochaetae (pilosity); length and density of microchaetae (pubescence); standard measurements and indices; distinct habitat preferences of the various species; and host selection by Polyergus lucidus, s. l. Our results leave little doubt that F. incerta n. stat., rev. stat. and F. biophilica n. sp. deserve recognition as species, that F. nitidiventris is a synonym of F. pallidefulva and that F. schaufussi is a synonym of F. pallidefulva. Thus, the current concept of schaufussi (incorrect in reference to the lectotype) must give way to the next available name for the same population, dolosa n. stat. In this paper, we provide diagnoses, qualitative morphological characteristics, tabulated quantitative characters, natural history notes for all species and a key to the workers. As occurs in other groups of closely related ant species (e.g