OLFACTORY RESPONSES OF IPS PLASTOGRAPHUS MARITIMUS LANIER (COLEOPTERA, SCOLYTIDAE) TO INSECT AND HOST-ASSOCIATED VOLATILES IN THE LABORATORY

Attraction of both sexes of Ips plastographus maritimus Lanier to bark -phloem-xylem discs of Monterey pine, Pinus radiata D. Don, was demons trated in the laboratory. Increasing concentrations of male and female volatiles trapped separately and released in a one-to-one ratio decre ased attraction for both sexes combined. Attraction of both sexes to v olatiles derived from males and females tunneling together in a one-to -one ratio increased with increasing concentration of extract. Attract ion of males and females to male-infested discs and to trapped male vo latiles increased with increasing dose of males or male extract. Attra ction of males and females to female-infested discs and to trapped fem ale volatiles was also demonstrated. The presence of females in male g alleries reduced the attractiveness of infested disks to both sexes co mbined. Increasing numbers of females, tunneling separately from males in the same disc, reduced attraction of males, but not females. When a constant attractive dose of male volatiles was released with increas ing doses of female volatiles, there was no difference in response of either sex when female volatiles were present compared with the respon se to male volatiles alone. When a constant attractive dose of male vo latiles was released with increasing concentrations of volatiles deriv ed from males and females tunneling together in a one-to-one ratio, at traction of I. p. maritimus decreased. Response of females was frequen tly higher than that of males to the same attractant source. Hence, bo th sexes produce an attractant, and both sexes tunneling together in t he same gallery reduce attraction of males and females to an attractiv e dose of male attractant.