Effect of Brood Type on Varroa-Sensitive Hygiene by Worker Honey Bees (Hymenoptera: Apidae)

Honey bees (Apis melliferaL.) (Hymenoptera: Apidae) have been selectively bred for varroa-sensitive hygiene (VSH), which is the removal of pupae that are infested byVarroa destructor Anderson&Trueman fromcappedbrood cells. This hygienic behavior is a complex interactionof bees and brood inwhich brood cells are inspected, and then brood is either removed or recapped. Previous work has shown that VSH bees uncap and remove signiÞcantly more varroa-infested worker pupae than nonhygienic bees do, but nothing is known about the reactions of VSH bees to mite-infested drone brood. This study compared the reactions of VSH bees with mite-infested worker and drone brood in a laboratory test and a Þeld test. VSH bees inspected brood cells containing mite-infested pupae of both types of brood, but they removed signiÞcantly fewer mite-infested drone pupae than mite-infestedworkerpupaeafter 1wk.This result suggests thatmitepopulations inVSHcolonies could increasemore rapidlywhendronebrood is available.Additionally, thepercentages of uncappedpupae and uncapped mite-infested pupae were positively correlated to the natural infestation rate of brood after a 24-h exposure, but not after an exposure of 1 wk. This result suggests that the rate of uncapping brood by hygienic bees may depend on the infestation rate, which gradually decreases with longer exposures to bees that remove mite-infested pupae from capped brood.