The ant Tapinoma sessile (Say) 1836 is one of the most widely distributed ants in North America; yet, it has received very little attention from biologists apart from its ability to infest houses. The original species description does not adequately account for the phenotypic variation present in this species of typically darkly concolored ant. In California, a bicolored morph was discovered that superficially resembles T. sessile; hence, its species status was questioned. Comparative morphometric analysis indicates that the bicolored ants are consistently distinguishable across a range of characters, and allometric techniques conclusively demonstrate that these two morphs are divergent. Based on the analysis of morphological data it was concluded that the bicolored ant is not T. sessile and is described as a new species, Tapinoma schreiberi. A neotype of T. sessile also is designated in this article, and measurement data are presented to assist taxonomists and delimit the morphological boundaries of T. sessile.