UC San Diego

Varroa destructor is a parasitic mite that threatens managed and feral Apis mellifera colonies worldwide. Managed honey bees are regularly treated with miticides to control for Varroa, but the use of these chemicals reduces bee fitness and leads to the evolution of miticide resistance in V. destructor. However, feral colonies, which tend to be more Africanized, may tolerate mites without chemical treatment. Some studies have shown Africanized colonies demonstrate increased hygienic behavior by removing more dead brood and by grooming more intensely, making them potentially more Varroa-resistant. Thus, comparing the behavior of feral and managed bees can reveal the potential role of social immunity in feral bee tolerance against V. destructor. These findings can better inform traits of interest for bee breeding programs. Interestingly, no differences in mite infestation were observed despite that managed bees were treated with miticides at multiple times throughout the year. This result suggests that feral colonies have ways to reduce their mite levels. There were no observed differences in the social immunity of feral and managed honey bees as measured by their hygienic, self-grooming, or mite biting behavior. However, we provide the first evidence that both feral and managed honey bees bite off mite forelegs at higher rates than other legs; mite forelegs contain chemosensory organs that mites use to find brood cells to reproduce in. Such biting may therefore impair mite reproduction. Future studies should therefore focus on other mechanisms that evidently allow feral bees to resist Varroa infestation.