In the United States, the word "pissants" or "piss ants" generally refers to nuisance ants that are known to invade homes. Such infestations may involve any of a number of small ant species, including Argentine, crazy, ghost, odorous house, pharaoh and white-footed ants.
The term was originally used in reference to several ant species native to certain European forests. The name came from the urine-like odor produced by the combination of formic acid from their venom and the pine needles and straw they used to build their mound-like nests. In English slang, "pissant" also describes an insignificant or irrelevant person or object.