Role of sex pheromones in reproductive isolation between two host races inAspidiotus cryptomeriae Kuwana (Homoptera : Diaspididae)

The reproductive isolation between two host races of Aspidiotus cryptomeria e was examined by comparing intra- and inter-racial responses of males to l ive virgin females and to sex pheromones in the laboratory. No inter-racial copulation of males to live females was observed for either sex combinatio n. These results indicated that ethological isolation was present between t he races. We showed by using a crude extracts test that both host races hav e female sex pheromones. Although an inter-racial response of males tai fem ale extracts was observed it was much weaker than the intra-racial response s, suggesting that the sex pheromone system plays an important role in repr oductive isolation between the two races. These results support the hypothe sis that each host race is a distinct species.