Average number of reproductive cycles performed by Varroa jacobsoni in honey bee (Apis mellifera) colonies

Due to the low fecundity of Varroa jacobsoni, it is presently not possible to explain satisfactorily the observed rapid build up of mite populations in APis mellifera colonies. The number of reproductive cycles, i.e. the number of times a mite enters brood cells to reproduce, has been suggested to be the key to this problem. Despite several studies on this aspect, large discrepancies in the published data remain. This paper describes a new experimental method for studying this aspect of the mites' biology in order to resolve this question. Colonies containing only worker bee brood were manipulated so they had discrete brood cycles. Colonies were kept in a mite-free area and infested with a known number of mites at the start of the study. To estimate the average number of reproductive cycles performed, the observed growth in the mite populations was compared with the theoretical growth of mite populations which performed different numbers of reproductive cycles, but with conditions otherwise similar to those observed in the study colonies. The level of mite drop was used as an indicator of the mite population. The average potential number of reproductive cycles required to explain the observed mite population growth was between two and three.