Componotus japonicus, commonly known as the Japanese carpenter ant, is a large, robust ant species native to Japan and parts of East Asia. These ants are easily identifiable by their black or dark brown coloration and their distinctively large size, typically measuring 8 to 12 millimeters in length. The species exhibits a two-segmented waist and prominent mandibles, which they use for foraging and nest building.

C. japonicus is often found in forested areas, nesting in decaying wood, but can also inhabit soil and leaf litter. They play a crucial role in their ecosystem by aiding in the decomposition of wood and enhancing soil health. The colonies are usually moderate to large, containing several thousand individuals, with a clear division of labor among workers, foragers, and reproductive individuals.

These ants are primarily herbivorous, feeding on honeydew produced by aphids, as well as plant nectar and other sugary substances. They are known for their aggressive behavior when defending their nests and are capable of inflicting painful bites. C. japonicus has adapted well to various environments, making it an important species in both natural and urban settings.