Electroantennogram responses of a parasitic wasp, Microplitis croceipes, to host-related volatile and anthropogenic compounds

The parasitic wasp Microplitis croceipes (Cresson) (Hymenoptera: Braconidae ) showed its own characteristic electroantennogram (EAG) response profiles to 13 host-related (cis-3-hexenol, alpha -pinene (R)-(+)-limonene (S)-(-)-l imonene, trans-beta -ocimene (+/-)-linalool, (-)-trans-caryophyllene, alpha -humulene, nerolidol, trans-nerolidol, cis-nerolidol, methyl jasmonate and indole) and four anthropogenic (2-diisopropylaminoethanol, 2,2'-thiodietha nol, 2-methyl-5-nitroaniline and cyclohexanone) volatile compounds. These p rofiles were similar between males and females except for 2-diisopropylamin oethanol, which elicited significantly larger EAG responses in males. Among the compounds tested, cis-3-hexenol, linalool and cyclohexanone elicited t he largest EAG responses. EAG responses were not influenced by the age of w asps between 1 and 13 days after emergence. EAG responses were dose-depende nt, and highly EAG-active compounds elicited significant EAG responses with less than 10 mug of the compounds at source. Quantification of compounds r eleased from an odour cartridge indicates that release rate is highly depen dent on the chemical nature of stimuli, showing up to 10 000-fold differenc es in the amount released between different compounds when the same amount was loaded in the odour cartridge. Wasps having undergone a behavioural tra ining regime to be attracted to either cyclohexanone or methyl jasmonate di d not show any differences in EAG responses from those of untrained wasps.