Figure 2. Behavioural context: effect of cVA release on attraction and effect of starvation on courtship.

(a) Chromatograms showing volatiles released by mating (top) and non-mating flies (bottom trace). Release of cVA increased from 8.1 ± 0.3 in non-mating flies (n = 8) to 43.4 ± 3.0 pg/min/fly in mating flies (n = 6) (Mann-Whitney test, V = 48, p < 0.001). (b) Male attraction towards a blend of vinegar and pheromone (volatiles collected from mating flies, non-mating flies, or synthetic cVA), compared to vinegar alone in a y-tube olfactometer. Males were attracted by volatiles from mating flies (n = 20), and not to volatiles from single flies (n = 22). Synthetic cVA equivalent to the amount released by mating flies (n = 25) induced significant attraction (Wilcoxon’s signed rank test; *p < 0.05, **p < 0.01). (c) Sexual receptivity of fed and starved females courted by either starved or fed males. (d) Effect of starvation of male courtship behaviour, towards either fed or starved females. Asterisks (c,d) show a significant effect of starvation (GLM, ***p < 0.001; n = 30). Photos by S. Lebreton.