Feeding behaviour in the bumble bee Bombus terrestris

Bumble bees (Bombus terrestris) are social insects that live in one-year colonies. Larvae are fed progressively by the workers up until the moment they pupate and transform into adults. An elaborate hypothetical scheme concerning the dynamics of feeding behaviour is presented. The central hypothesis is that larvae emit a hunger-signal that can inform workers about their nutritional status and thereby influence the feeding behaviour of the workers. In addition it is hypothesized that the receptivity of the workers for the hunger signal and their motivation also influence their decision whether or not to go and feed larvae. This contrasts with the prevalent view that workers impose a feeding regime on larvae, who passively undergo their rearing. Worker (feeding) behaviour in a number of colonies was recorded and experiments were conducted in order to elucidate several aspects of the dynamics of feeding behaviour. In the experiments presented here the strength of the hunger signal was manipulated in various ways: by starving larvae, feeding artificial food to larvae in vivo, and varying the number of larvae. The results of the experiments indicate that indeed in B. terrestris larvae emit a short-range hunger-signal that can be perceived by workers and that can trigger worker behaviour such as ``long pollen eating'' (which usually precedes feeding) and feeding larvae. This strongly suggests that a feeding regime is not simply imposed on larvae by workers. However, the motivation of workers also plays a decisive role in feeding behaviour.