Food and humidity affect sex pheromone ratios in the stink bug, Euschistus heros

Male stink bugs, Euschistus heros , only produce the three‐component sex pheromone blend consisting of methyl‐(2 E ,4 Z )‐decadienoate, methyl‐2,4,6‐trimethyldodecanoate and methyl‐2,4,6‐trimethyltridecanoate in a constant ratio of 53 : 3 : 44, respectively, when provided with a food source (green beans, Phaseolus vulgaris ). When volatiles are collected from insects with drinking water, humidified air, or under dry conditions, the insects stop producing two components (methyl‐2,4,6‐trimethyldodecanoate and methyl‐2,4,6‐trimethyltridecanoate) after 1 day and increase the amount of defensive compounds produced [e.g. ( E )‐2‐hexenal, decane]. Methyl‐2,4,6‐trimethyltridecanoate is able to change the behaviour of females but not males. Dual‐choice olfactometer bioassays with synthetic standards of all three components, as well as the ternary mixture in the correct ratio, induce a response from females but not males, indicating that all three components have a role in sexual communication. Thus, the dietary conditions under which volatile collections are carried out are crucial for determination of the precise sex pheromone blend.