Life Cycle of V. destructor
Life Cycle of V. destructor
The life cycle of the mite can be divided into phoretic and reproductive phases. The reproductive phase begins when a mature female leaves her adult host, enters a brood cell containing a worker or drone larva shortly before it is capped, and sequesters herself in the bottom of the cell. Soon, the cell is capped; and shortly thereafter, the immature bee enters the pupal stage. Egg-laying commences about 60 hours after a cell is capped, and both mother and offspring feed on the host’s hemolymph. Mature offspring mate within the cell, but only mature females survive outside the cell.
The number of offspring that reach maturity is positively correlated with the length of the host’s capped stage, which is greatest for drones, intermediate for workers, and shortest for queens. Mites that reproduce on drone brood average 2.2 to 2.6 female offspring per host, while those reproducing on worker brood average 1.3 to 1.4 female offspring per host. Mites cannot reproduce on queen brood due to its short capped period. Not surprisingly, mites are found more often on drone brood than worker brood, with average differences between 5- and 12-fold. Mites are only rarely found on queen brood.
The phoretic phase begins when the host emerges from its cell as an adult bee. The mature female mite may leave the cell with its adult host, or it may walk out of the cell and acquire an adult host. Mites remain on an adult host for a few days or weeks before entering a brood cell for the next round of reproduction. Mites are found twice as often on bees in the brood nest as on bees in the honey supers, and 10 times as often on brood nest bees as on foragers.
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