VARIATION IN SEMIOCHEMICAL-MEDIATED PREY-PREDATOR INTERACTION - IPS-PINI (SCOLYTIDAE) AND THANASIMUS-DUBIUS (CLERIDAE) (REPRINTED FROM JOURNAL OF CHEMICAL ECOL, VOL 17, MARCH, PG 515-524, 1991

The bark beetle Ips pini (Say) displays variation in its response to and production of enantiomeric blends of its pheromone ipsdienol. One of the principal predators of Ips pini is Thanasimus dubius (F.), which uses ipsdienol as a kairomone for prey location. During 1988 and 1989, in Wisconsin and Michigan, the response of both species to a range of enantiomeric blends of ipsdienol was investigated. Blends tested had the following ratios of the (S)-(+) to (R)-(-) enantiomers: 3%:97%, 25%:75%, 50%:50%, 75%:25%, and 97%:3%. Either 75% (+):25% (-) or 50% (+):50% (-) ipsdienol captured the most Ips pini in both years at both sites. The 25% (+):75% (-) blend also caught more Ips pini than the control during both years at both sites. All blends tested were attractive to Thanasimus dubius in both years at both locations. Blend preferences of both species were variable and labile at both sites. Response patterns of both species in Wisconsin were different from those in Michigan each year. Furthermore, response patterns of both species to the ipsdienol blends changed from 1988 to 1989 at both locations. A genetic component to this variation would permit predator-prey coevolution, as well as the development of resistance by Ips pini to management strategies based on mass-trapping with single blends.