DIFFERENTIAL HYGIENIC BEHAVIOR TOWARDS VARROA-JACOBSONI IN CAPPED WORKER BROOD OF APIS-CERANA DEPENDS ON ALIEN SCENT ADHERING TO THE MITES

Five Apis cerana colonies in Newton hives in Allahabad, northern India, were used in the experiments. Female Varroa jacobsoni, in the reproductive phase, were transferred from drone brood into worker brood in the same colony (1), or into worker brood in another colony (2). Some introductions (3) involving dead mites washed with ethanol and pentane (and therefore odour-free) were also carried out. Mites collected from a single Apis mellifera colony were introduced into some A. cerana brood (4), and some 'sham inoculations', involving the opening and closing of brood cells without the introduction of a mite, were made (5). After 5 days, in (1) and (5) only about 10% of manipulated cells were found empty. In (1) and (3), in addition, about 40% of cells had been opened, the mites removed, and the cells, still containing pupae, resealed. About 50% of manipulated cells were untouched. The percentage of empty cells was much higher in (2), and even higher in (4). The results indicate that differences in hygienic behaviour are due to scent cues adhering to the mites. The incidence of this type of behaviour in the Apis mellifera colony was extremely low. The significance of the differential hygienic behaviour observed in the tolerance of V. jacobsoni infestations is discussed.