Mite infestation during development alters the in-hive behaviour of adult honeybees.

Honeybee colonies (Apis mellifera) host a number of parasites, among which the mite Varroa destructor has been implicated in colony losses recorded around the world in recent years. Although many studies have been carried out on the direct and indirect damage caused by the mite to its host, the possible influence of mite infestation on the in-hive behaviour of honeybees has received little attention so far; moreover, to our knowledge, no behavioural study has been performed on adult bees infested during the pupal stage, which is when the mite causes most of its detrimental effects. In order to assess any possible consequence of infestation on the in-hive behaviour of honeybees, we carried out detailed observations on adult bees artificially infested during the pupal stage. We recorded a higher proportion of inactive bees among the infested ones; moreover, we observed that infested bees are less involved in tending larvae and dealing with hive duties compared to their uninfested mates. These results allow to draw some hypotheses which could be tested using the infestation method presented here.