Fig. 4. (A) Learning rate of H. virescens females showing the conditioned response (proboscis extension) to CS+ and CS- (irrespective of which odorant was the CS+) in extinction tests after differential conditioning with the three odorant pairs [racemic linalool (L) and ß-myrcene (M), L and ß-ocimene (O) and O and M, 12 conditioning trials, N=103-106 for each pair)]. The concentrations used were 0.1 mg racemic linalool, 10 mg ß-ocimene and 100 mg ß-myrcene. The moths responded significantly more to the CS+ in all cases (exact McNemar test, P<0.05). (B) Learning rate in extinction tests after differential conditioning with the six pairs of three odorants [each odorant (CS+ and CS-) was presented pseudo-randomised six times, N=51-53 for each pair]. There was a significant discrimination between the CS+ and CS- in the M+L-, M+O- and O+M- groups (exact McNemar test, P>0.05, marked with an asterisk). For the odour pair M L, an asymmetry appeared as the insects showed a significantly higher discrimination when M was the rewarded odorant than when L was the rewarded odorant CS+ (Fisher's exact test, P<0.05).