A larval hunger signal in the bumblebee Bombus terrestris

Larvae of Bombus terrestris, a pollen-storing bumblebee, are dependent on progressive provisioning by workers. We test the hypothesis that larval cuticular chemicals can act as a hunger signal. We first show with a new classical conditioning experiment, using a Y-shaped tube, that workers can be trained to prefer the extracts of normally fed larvae over those of starved larvae. This proves the ability of workers to discriminate between larval extracts. Second, we show in a bioassay that workers also use these perceived differences to feed larvae according to their nutritional status. Larval broods sprayed with the extracts of the starved larvae were fed significantly more than larval broods sprayed with the extracts of normally fed larvae or with the solvent (n-pentane) only. We therefore conclude that B. terrestris larvae signal their need for food via their cuticular chemicals, and discuss the extent to which this form of communication could give larvae some control over their development. Received 2 September 2005; revised 11 April; accepted 24 April 2006.