Bees with Varroa Sensitive Hygiene preferentially remove mite infested pupae aged ≤ five days post capping

Suppressed Mite Reproduction (SMR) is a trait of honey bees that provides resistance to Varroa destructor. The mechanism of resistance in SMR bees is the removal of infested pupae from capped brood, so a better name is VSH bees (acronym for Varroa Sensitive Hygiene). This study compared the removal of infested brood by VSH and control bees to determine whether VSH bees removed infested pupae of different ages at similar rates. A pair of infested combs containing all stages of pupae were transferred into each host colony (six VSH and six control colonies) for 40 hours. VSH bees removed significantly more (55%) infested cells (singly and multiply infested), than controls (13%). They removed significantly more (66%) singly infested pupae aged from one to five days post capping (cohort A) than did controls (16%). The two types did not differ in the removal of singly infested pupae aged five to 10 days post capping (cohort B) (5-22%). Many pupae were found in uncapped cells at the end of the test, and most of the uncapped pupae were infested with mites. None of the uncapped cells contained prepupae, the development stage occurring during the first three days post capping. Thus, removal of infested pupae may be triggered by stimuli in cells with pupae aged 3-5 days post capping.