SECONDARY ATTRACTION IN GNATHOTRICHUS-RETUSUS AND CROSS-ATTRACTION OF GNATHOTRICHUS-SULCATUS (COLEOPTERA, COLYTIDAE)

Laboratory bioassays indicated that frass produced by Gnathotrichus retusus males and male gut extracts were attractive to both sexes of beetles. The frass became attractive to females within 2 days of the commencement of boring activity, and attractive frass was produced for at least lOdays. Attraction of frass rose sharply after pairing of males with females. However, this increase in attraction could be due to increased boring activity and pheromone production by males following establishment of the mutualistic fungus. In field trapping experiments, male-infested logs were always highly attractive, but in one experiment, female-infested logs and logs infested by both sexes were also attractive. Thus, females could be involved in secondary attraction. High cross-attraction of G. sulcatus to G. retusus infested logs in field experiments, as well as a moderate but significant response by G. retusus to sulcatol in the laboratory, suggests that they share sulcatol as a common pheromone. © 1979 Plenum Publishing Corporation.