Synonyms and other taxonomic changes
In the news: This species was described by 19th century American entomologist Thomas Say, from the utopian community of New Harmony, Indiana, but the types were lost. An Aug 2010 paper designated a neotype from Thomas Say's grave site. Cool, eh?
Explanation of Names
Tapinoma is derived from a Greek word for fallen or more precisely, dejection. The author may have referred to its general lowliness, to the physically depressed (slightly flattened) head and gaster, or to its humble coloration (In any of these ways it can make sense.)
The adjective sessile means stalkless, in reference to the appearance of the gaster in most views of this ant. In fact, as clearly visible in the following image, this ant has a "stalk" or petiole, but it is small and lacks a node.
Palp formula 6,4.
Mandibles with 10+ teeth, apical, subapical and 4th from apex notably larger than the rest.
Visible gastral tergites 4.
sexuals (both genders) 4-5mm
The low, nodeless petiole is distinctive, but often is not readily visible. However, it is clearly seen in these images:
Southern Canada to northern Mexico, coast to coast.
Generally, any mesic or moist (but infrequently flooded) habitat. (1)
Virtually ubiquitous except in hot deserts (only in oases), cold alpine forests (but found in alpine meadows), or above timberline. Very abundant in the "human habitats" of most of the USA and southern Canada, but diminishing abundance in the Sunbelt.
Active early in spring, often in people's kitchens.
Mating flights are in May south, June north.
Sweets and scavenged protein and fats.
This ant appears to have distinct spring and summer forms, larger and darker individuals overwinter, smaller and paler ones are more abundant during the "dog days".
Sexuals fly late spring.
Alates are reared in spring, not uncommonly in wall spaces or window frames of houses, but naturally in the upper portions of leaf piles, under bark, etc.
Recent genetic studies indicate this may turn out to be a complex of 4 or so cryptic species.