Honey bees performing varroa sensitive hygiene remove the most mite-compromised bees from highly infested patches of brood

Varroa destructor is a key contributor to honey bee (Apis mellifera L.) colony losses that threaten global economies. Some colonies, especially those displaying high levels of hygiene behaviour targeted towards V. destructor-infested cells, survive mite infestation. Worker bees displaying varroa sensitive hygiene (VSH) open infested brood cells and remove the contents, thereby suppressing mite reproduction. This study identifies features that distinguish cells uncapped by bees performing VSH from infested cells that VSH bees ignore. Brood cells targeted and uncapped by VSH bees were found to be more likely to contain multiple foundress females than non-targeted cells. They also contained higher numbers of mite offspring, and lay within brood cell patches that were more highly infested with V. destructor than were the surrounds of infested cells ignored by VSH bees. This study is the first to identify cell surrounds as a potential source of signals influencing the behaviour of bees performing VSH.