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Detection and interpretation of chemical cues is essential for Varroa destructor Anderson and Trueman, an important parasite of honey bees (Apis mellifera L.), to complete its life cycle. We collected volatiles from honey bee brood at various developmental stages and screened for V. destructor electrophysiological responses to these with gas chromatography-linked electrotarsal detection. Volatile collections contained several methyl-alkanes that evoked electrophysiological responses from V. destructor. Moreover, odors in honey bee colonies that regulate honey bee colony structure and function were also detected by V. destructor. Collections from mid- to late-stage larvae had detectable levels of low-volatility odors identified as components of the honey bee brood pheromone and branched alkanes likely originating from brood cuticle. Among these, several mid- to heavy-molecular weight compounds elicited high proportional electrophysiological responses by V. destructor relative to their abundance but could not be identified using chemical standards of previously documented honey bee brood odors. We suggest further investigation of these unknown volatiles and future behavioral assays to determine attractiveness/repellency (valence) of those identified through chemical standards.

Olfaction is a key sensory modality for many arthropods and could be used as a tool in pest management through manipulation of pest behavior. Management of Varroa destructor, important parasitic mites of honey bees, could be improved through better understanding of the chemical ecology of this host-parasite relationship. We refined techniques of mounting mites to obtain electrophysiological recordings (electrotarsograms) of their responses to synthetic odor stimuli. Results of 271 electrotarsogram recordings from V. destructor revealed responses to 10 odorants relative to solvent controls. Electrotarsogram responses to methyl palmitate, ethyl palmitate, and 2-heptanol were highest at the lowest stimulus loading (10 ng) we tested, suggesting that V. destructor may have acute sensitivity to low concentrations of some odors. Results suggest that odorant origin (e.g., methyl oleate from honey bee larvae, geraniol from adult honey bee alarm pheromone, and α-terpineol, a plant secondary metabolite) can influence the degree of electrophysiological response. Varroa destructor tended to be more responsive to known attractants and repellents relative to previously unexplored odorants and some repellent terpenes. Electrotarsograms offer the potential for screening odors to determine their importance in V. destructor host detection.