The main aim of this research is that the relationships between kin recognition behaviors and genetic structures of critical invasive ants, Argentine ant (Linepithema humile) in western Japan. The North Argentina-derived small ant species has high fecundity and aggressiveness, then it gives giant impact against native ecosystem. Now, it has been widespread and established unicolonial over 6,000 km long from Spanish to Italia. Since 1993 the ants has invaded in Hiroshima, and expanding in western Japan. In this study we assessed kin recognition behaviors among 8 Argentine ant populations and estimated relatednesses using CAP-PCR. Workers of Kure population had kin recognition abilities, however, rest of the populations had no effective aggressive behaviors even over 300 km away from its colonies. Although the estimated relatednesses in longer settled populations were reached nearly 0, most populations had shown about 0.3. These data indicated differences with European Argentine ant populations, and should discuss evolutionary and ecological aspects of its Japanese populations.