Fig. 5.

The habituation phenomenon generalizes to caffeine but not to aristolochic acid in caterpillars lacking their medial styloconic sensilla. We show the percentage of control response by nonhabituated (A) and nonhabituated (B) caterpillars during two sequential brief-access taste tests. The insects received the control diet in the first test and one of the following bitter diets in the second test: salicin (157 mm/kg diet; fresh mass), caffeine (7.7 mm/kg diet), or aristolochic acid (0.76 mm/kg diet). We calculated the percentage of control response by dividing total intake from a bitter diet by total intake from the corresponding control diet (and then multiplying this number by 100). To determine whether a bitter diet elicited an aversive response (i.e., elicited a median response that was significantly <100%), we used a one-sample Wilcoxon matched-pairs signed-rank test (*p ≤ 0.05). A dashed line was placed at 100% for comparison. Each bar indicates the median ± median absolute deviation (n = 20–24 caterpillars per median).