Colony and Nest Structure of the Japanese Pirate Ant, Polyergus samurai, and Its Host, Formica japonica (Hymenoptera: Formicidae)

The nests of the social parasite ant, Polyergus samurai, and of its host ant, Formica japonica, were excavated and their colony traits and nest structure were examined. Single queen colonies were most frequent in both species, and only one of 13 F japonica colonies contained two queens. The number of E japonica workers in P. samurai nests was much larger than that of E. japonica, suggesting the considerable reduction of future workers in the F. japonica colonies raided by P. samurai workers. Although the nest sizes of P. samurai were larger than that of F. japonica nests, the nest structures were similar to each other. The nesting behaviors of F. japonica workers may not be affected by parasitism by P. samurai, but the increase of colony size in the parasite colony results in the extension of nest dimensions.