Methyl 6-Methylsalicylate: A Female-Produced Pheromone Component of the Parasitoid Wasp Spalangia endius

Sex-pheromone-related behavior and chemistry were studied in the wasp Spalangia endius Walker (Hymenoptera: Pteromalidae), a pupal parasitoid of the house fly, Musca domestica L. (Diptera: Muscidae). Males responded behaviorally to female extracts by arrestment, whereas females did not arrest to male extracts. In a comparison of male and female extracts by gas chromatography-mass spectrometry (GC-MS), two female-specific compounds were found. One was identified as methyl 6-methylsalicylate (gas chromatographic retention time and mass spectrum versus an authentic standard), but the chemical structure of the second compound is still unknown. Male antennae were sensitive to both compounds in electrophysiological tests (GC-EAD). Males responded behaviorally to methyl 6-methylsalicylate by arrestment, but did not arrest to the second compound. Methyl 6-methylsalicylate has been reported previously from some ant and beetle species, but never from the Pteromalidae. Chemical analysis of the extracts and the male behavioral results are consistent with the hypothesis that methyl 6-methylsalicylate functions as a female-emitted pheromone component at short range, but the exact role of both compounds in intersexual interactions in S. endius remains to be determined.