Electroantennogram responses of mediterranean fruit fly,Ceratitis capitata (Diptera: Tephritidae) to trimedlure and itstrans isomers

Electroantennograms (EAGs) of unmated laboratory-reared male and femaleCeratitis capitata (Wiedemann) were recorded in response to the attractant trimedlure [tert-butyl 4(and 5)-chloro-trans-2-methylcyclohexane-1-carboxylate] and its fourtrans isomers. For both sexes, the magnitude of the EAG response was relatively low as compared to other previously tested compounds (i.e., plant volatiles). Dosage-response curves generated for all TML isomers revealed that flies responded to increasing dosages over a relatively narrow range (two to three log steps). Responses for both sexes peaked at ca. 10 μg dose for all isomers. Antennal response in males was greatest to the C isomer followed by the B₁, A, and B₂ isomers, while responses of females were greatest for the A isomer followed by B₁, C, and B₂. Both sexes exhibited a long recovery period for the response potential to return to baseline at doses above 1 μg for all of the isomers tested, except for B₂. The low EAG sensitivity to trimedlure and the apparent EAG selectivity to the C isomer in males are discussed in relation to the known field attractancy of males to the C, A, B₁, and B₂ isomers.