1.8. Olfactory detection
Bees from hygienic colonies are particularly responsive to olfactory-based stimuli associated with diseased brood. All bees can perform uncapping and removal behaviours, but bees that detect abnormal brood odours at a low stimulus level may rapidly initiate uncapping behaviour, resulting in the removal of diseased brood before it becomes infectious (Wilson-Rich et al., 2009). Individual bees from the rapid-hygienic line bred by Spivak et al. exhibited significantly increased sensitivity to the odour of chalkbrood disease at lower concentrations compared with bees from the slow-hygienic line, based on electrophysiological recordings of nerve impulses from the antennae (EAG), by proboscis-extension response conditioning (PER), and by isolation of volatiles from chalkbrood–infected larvae for use in field bioassays (see detailed methods in: Masterman et al., 2000, 2001; Gramacho and Spivak, 2003; Spivak et al., 2003; Swanson et al., 2009; and general methods of EAG and collection of volatiles in the BEEBOOK paper on chemical ecology methods (Torto et al., 2013) and of PER in the BEEBOOK paper on behavioural methods (Scheiner et al., 2013).