The Varroa paradox: infestation levels and hygienic behavior in feral scutellata-hybrid and managed Apis mellifera ligustica honey bees.

The Varroa destructor mite is a parasitic threat to managed and feral honey bee colonies around the world. Beekeepers use miticides to eliminate Varroa in commercial hives, but these chemicals can diminish bee health and increase miticide resistance. In contrast, feral honey bees have developed multiple ways to counteract mites without chemical treatment. We compared mite levels, grooming habits, and mite-biting behavior between feral Africanized honey bees (genomically verified Apis mellifera scutellata hybrids) and managed Italian honey bees (A. mellifera ligustica). Surprisingly, there was no difference in mite infestation levels between scutellata-hybrids and managed bees over one year despite the regular use of miticides in managed colonies. We also found no differences in the social immunity responses of the two groups, as measured by their hygienic habits (through worker brood pin-kill assays), self-grooming, and mite-biting behavior. However, we provide the first report that both scutellata-hybrids and managed honey bees bite off mite chemosensory forelegs, which the mites use to locate brood cells for reproduction, to a significantly greater degree than other legs (a twofold greater reduction in foreleg length relative to the most anterior legs). Such biting may impair mite reproduction.

Seasonal variation in defense behavior in European and scutellata-hybrid honey bees (Apis mellifera) in Southern California.

Nest defense in the honey bee (Apis mellifera) is a complex collective behavior modulated by various interacting social, environmental, and genetic factors. Scutellata-hybrid ("Africanized") honey bees are usually considered to be far more defensive than European honey bees which are therefore preferred for commercial and hobbyist beekeeping. In the most recent zone of scutellata hybridization, the southern USA, the degree to which this defensiveness differs among current strains, and the extent to which defensiveness varies across a season has not been measured. We quantified the levels of A. m. scutellata ancestry in colonies and conducted a seasonal assessment (May through November) of colony nest defensiveness in feral scutellata-hybrid and a popular lineage of European honey bee commonly used in managed environments (sold as A. mellifera ligustica) hives at two apiaries in Southern California. Standard measures of defensiveness were low in both scutellata-hybrid and European colonies during May. Defensiveness increased during the later months of the study in scutellata-hybrid colonies. Most measures of defensiveness did not increase in managed colonies. Defensiveness in the scutellata-hybrids appears lower than what has been previously documented in Brazil and Mexico, possibly due to their lower proportion of A. m. scutellata ancestry.