Figure 3. Representative coupled gas chromatography-electroantennogram analysis of repeated, alternate injections of synthetic (R)- and (S)-desmolactone using an antenna from a male Desmocerus a. lacustris.

Upper trace is the chromatogram, lower inverted trace is the electroantennogram signal from the beetle antenna. DB-5 column, 40°C/1 min, then 10°C/min to 275°C, hold 40 min. Large peaks interspersed between the (R)- and (S)-desmolactone peaks on the GC trace are from the solvent used in the injections.