Biological notes of Probolomyrmex okinawaensis Terayama & Ogata collected in Yonagunijima Island, and five species of Probolomyrmex collected in Japan and Southeast Asia

A colony of Probolomyrmex okinawaensis, composed of one dealate queen and four workers, was collected in Yonagunijima Isl., the westernmost island of Japan, as the first record outside of Okinawajima Isl. The colony was kept in the laboratory for behavioral observations. The ants attacked and fed only on polyxenid millipedes. Mature colony size was small: an alate queen was produced when the number of workers was ca. ten under laboratory conditions. The number of ovarioles was two in both castes. Larvae were found hanging from the glass ceiling of the nest chamber. We also report biological data of five species of this genus collected in Southeast Asia and Japan and discuss our results in relation to the available published information on this genus. The biological characteristics mentioned above are commonly found in these species.