A semiochemical from brood cells infested by Varroa destructor triggers hygienic behaviour in Apis mellifera

Hygienic behaviour of bees towards mite infested brood is involved in the tolerance of some bee strains to Varroa destructor. The stimuli triggering hygienic behaviour are olfactory cues emanating from cells containing infested brood but their identity is still unknown. After confirming the capacity of bees to detect and empty mite-infested cells, we studied the volatile chemicals released by artificially infested worker brood cells by means of SPME-GC-MS. The identified chemicals were then bioassayed by comparing the bees' hygienic behaviour towards treated cells into which 1 mu g of each compound was injected and control cells which received the solvent alone. Z-(6)-pentadecene significantly increased the number of cells emptied by the bees.