Kairomonal effects of sawfly sex pheromones on egg parasitoids

The response of the two europhid egg parasitoid species Chrysonotomyia rufo rum and Dipriocampe diprioni to sex pheromones of their sawfly hosts Diprio n pini and Neodiprion sertifer was studied in olfactometer bioassays. Femal es of C, ruforum were arrested when exposed to odor of the tested major sex pheromone components of Diprion pini [acetate and propionate of (2S,3R,7R) -3,7-dimethyl-2-tridecanol] or Neodiprion sertifer [(2S,3S,7S)-3,7-dimethyt -2-pentadecyl acetate]. This behavioral response of C. ruforum was observed whether (1) parasitoid females had oviposition experience with D. pini egg s or not, (2) parasitoid females emerged from D, pini eggs of a French popu lation or from N. sertifer eggs of a Finnish population, and (3) the tested sex pheromone concentration was low (1 ng/mul hexane) or high (100 ng/mul hexane). However, C, ruforum did not behaviorally respond to a stereoisomer of the major sex pheromone component of N. sertifer, which is known to act as a sex pheromone antagonist [antagonist = (2S,3R,7R)-3,7-dimethyl-2-pent adecyl acetate]. Thus, C. ruforum responded stereospecifically to the S,S,S configured pheromone of N. sertifer but not to the S,R,R configuration. Fe males of the parasitoid D, diprioni were also arrested by the tested major sex pheromone components of the host D. pini. The kairomonal effects of dip rionid host sex pheromones on these egg parasitoids are compared to known r esponses of egg parasitoids to lepidopteran sex pheromones.