Genus Tapinoma Foerster ^HNS

T. melanocephalum (Fabricius) ^HNS is an introduced species, not definitively established in the state. T. sessile (Say) ^HNS is a very common ant, found in almost all habitats in California except deserts and areas invaded by Linepithema humile ^HNS. T. sessile ^HNS shows substantial variation in size and color. At scattered locations in California a bicolored (orange and black) form of T. sessile ^HNS occurs sympatrically with the typical unicolored dark brown/black morph. Workers of intermediate color have also been observed, suggesting that the two forms are conspecific. An alternative interpretation is that there are two species which occasionally exchange genes, perhaps analogous to the situation between Forelius mccooki ^HNS and F. pruinosus ^HNS and between Dorymyrmex bicolor ^HNS and D. insanus ^HNS.

Species identification: key in Creighton (1950a). Additional references: Meissner and Silverman (2001), Smith (1965), Wang and Brook (1970).