Abstract: Microplitis mediator is one of the key parasitoid wasps which attack cotton bollworm Helicoverpa amigera. The odors released from host plants serve vital roles in its host finding behavior. Electroantennograms were recorded from female Microplitis mediator to 17 cotton volatile compounds. The EAG differences between female and male wasps to 6 compounds were compared, and EAG doseresponse curves were also constructed for females to 4 compounds. Aliphatic compounds elicited the largest EAGs. Aromatic derivatives elicited moderate EAGs, while terpenoid elicited the lowest EAGs. No sexual difference was found in EAGs to 6 compounds. The load thresholds for hexanal, acetophone and nonanol were 25 μL, while that for bezenaldhyde was 250 μL. None of the compounds reached saturation at the stimulus load series.

Key words: Microplitis mediator, volatile compounds, electroantennogram responses, dose-response curves