Monomorium carbonarium, also referred to the little black ant in North America, is a species of ant native to North America and Europe. It is a shiny black color, the workers about 1 to 2 mm long and the queens 4 to 5 mm long. It is a monomorphic species, with only one caste of worker, and polygynous, meaning a nest may have more than one queen. A colony is usually moderately sized with only a few thousand workers.