Polyergus samurai

Abstract: Raiding behavior of the Japanese slave-making antPolyergus samurai was investigated in the field. Raiding trips occurred from early June to early September. A raiding column of several hundreds workers would rush into a target nest and rob mainly worker pupae of the host species,Formica (Serviformica) japonica. Most trips occurred on sunny days. Air temperature, soil temperature, relative humidity, and radiation energy at the ground surface were significantly different between days with and without raiding trips. Nuptial flights occurred on hot, sunny days, and mostPolyergus colonies released alates simultaneously. Behaviors of newly mated queens are also provided and are compared with otherPolyergus species.

Abstract: Comparisons of cuticular hydrocarbons between workers of the dulotic ant Polyergus samurai and its slave, Formica japonica, were carried out. Gas chromatography–mass spectrometry showed that the slave-maker and its slave shared the major cuticular hydrocarbon compounds, but possessed several minor products unique to each species. No difference in hydrocarbon composition was detected between enslaved and free-living F. japonica workers, suggesting that association with P. samurai has no qualitative effect on hydrocarbon composition in these ants. Principal component analyses of the cuticular hydrocarbon profiles (CHP) revealed that (i) CHP was species specific in a given mixed colony; and (ii) among mixed colonies, P. samurai workers had species-colony specific CHP, while the same feature was not always found in enslaved and free-living F. japonica workers. Therefore, a ‘uniform colony odor’ in terms of CHP is not achieved in naturally mixed colonies of P. samurai nor those of its slaves, F. japonica.

Abstract: Founding queens of the obligatory social parasite ant Polyergus samurai usurp the host Formica japonica colony. The queen secretes chemicals from its gaster when killing the host queen. At this time, the parasite queen is hardly attacked by host workers. We hypothesized that the queen's secretion acts as a repellent to deter host workers' aggression during host queen killing. Gas chromatograph-mass spectrometry analyses confirmed that the chemical composition of Dufour's gland contents of P. samurai queens was almost identical to the chemicals remaining on the body surface of host Formica queens killed by them. Host F. japonica workers were used for bioassays. In an encounter with an intruder ant, the workers' aggression to the intruder was reduced significantly when Dufour's gland extract was applied to the intruder. Treatment of workers with the gland extract significantly increased the receding behavior of nestmates. The host workers receded from a glass dummy treated with the gland extract. The time necessary for a worker to get over a barricade applied with gland extract was significantly longer than that of controls. These results strongly suggest that Dufour's gland secretion acts as a repellent allomone.