The spatial distribution of dispersal-phase adult Varroa destructor mites on two strains of the honey bee (Apis mellifera) in New Zealand

The ectoparasite Varroa destructor (hereafter Varroa) poses a major threat to Western honey bee, Apis mellifera, populations. Synthetic chemical mite control treatments can have negative effects on bee health and are becoming less effective as mites develop pesticide resistance. A deeper understanding of the behaviour and adaptations of Varroa, and its interactions with A. mellifera, may aid in designing mite control strategies. This study investigates the host-parasite dynamics of A. mellifera and Varroa by examining the spatial distribution of adult dispersal-phase mites on a Varroa-susceptible strain and a Varroa-resistant strain of New Zealand honey bees. Mite distribution patterns in previous investigations are reviewed and compared, with differences between strains examined to determine whether parasitisation patterns reflect inherent mite resistance in a resistant population. No significant difference was observed between the spatial distribution of mites in the susceptible and resistant bee populations. Consistent with previous investigations, a significant asymmetry in mite location was observed. A total of 63.1% and 62.0% of metasoma mites found on the left side of the bee, and 83.5% and 85.5% found on the third abdominal segment, for Varroa-resistant and Varroa-susceptible bee populations, respectively. The mechanism of resistance strain therefore seems unlikely to be associated with differences in mite parasitisation patterns. Whether this asymmetric distribution is a result of parasite or host behaviour is unclear, however, discovering the underlying reason for this pattern of mite parasitisation may reveal information about the host-parasite relationship that could be exploited to devise novel mite control methods.