Fig. 4.

Contact with the odor source is not required to enhance food consumption. (A) Feeding score of mated Canton-S female flies offered 50 mmol l⁻¹ glucose in the presence or absence (control, mineral oil) of isoamyl acetate (IA) 1:20 v/v (loaded on filter paper); flies could smell but could not contact the odor source (as shown in Fig. 1A, right). Differences were statistically significant (P<0.005, two-tailed Mann–Whitney test). (B) Relative feeding scores of Canton-S flies offered food in the presence of isoamyl acetate volatiles with (left) without (right) the ability to contact the odor cue. For each vial, the relative feeding score was calculated by dividing the feeding score in the presence of the odor by the average feeding score of control flies (two-tailed Mann–Whitney test, P>0.05). (C) Feeding scores of mated females from a different strain of D. melanogaster (14021-0231.199, abbreviated as 199) offered 50 mmol l⁻¹ glucose in the presence or absence of isoamyl acetate volatiles (*P<0.05, two-tailed Mann–Whitney test). As with Canton-S flies, volatile cues were sufficient to enhance feeding. (D) Feeding scores of mated female Canton-S flies offered 50 mmol l⁻¹ glucose in the presence or absence of apple cider volatiles (40 µl loaded on filter paper or 40 µl of water). As with single odorants, complex odor mixtures can also enhance feeding. In all cases, boxplots indicate the median feeding score (horizontal line within the box), the 25th and 75th percentiles (lower and upper margins of the box), and the 10th and 90th percentiles (whiskers); circles show individual data points.