A function of the male pheromone of Leptoglossus australis (Fabricius) in its migration process was investigated on Ishigaki Is., the southernmost part of Japan. It was observed that the immigration of adults into particular fields of bitter gourd or loofah occurred suddenly within a short period of time. Immigrants landed mostly on a male-baited cage placed in a cucurbit field (a host plant of the bug) rather than on crop plants themselves without males, suggesting that cues inducing landing of immigrants are not their host plants, but the pheromone emitted by males. Moreover, an egg parasitoid, Gryon pennsylvanicum (Ashmead) (Hymenoptera: Scelionidae), was attracted to the male pheromone of L. australis, which may act as a kairomone for host searching of the parasitoid.