Peter > It has been known for a long time that mites are sensitive to chemical or odor cues in the hive. New research affirms this


This research also supports that there are attractant compounds driving the behavior.  


>V. destructor enters a brood cell containing a bee larva 15 to 20 h before worker brood cells are sealed and 40 to 50 h before drone brood cells are sealed (11). The mite does not reach the brood cell on its own but is carried there by a nurse bee, which is abandoned only a short distance from the bee larva that will be invaded (10). Apart from some physical stimuli, such as the distance from the bee larva and the cell rim (40), several chemicals mediate the attraction of the mite toward the brood and the following arrestment. 

>V. destructor shows a strong preference for drone brood. In A. mellifera carnica colonies, for example, drone brood is infested approximately eight times more frequently than worker brood (34); this preference could be due to the presence of greater amounts of attractant compounds either on drone larvae (63, 111) or in the larval food contained in such cells (89), as well as to the longer duration of the invasion period (11) and differences in the number of visits made by infested nurse bees to drone brood compared to worker brood. 

>In a brood comb, it is common to find larvae infested by two, three, or more mites as well as many cells that are not infested. This observation illustrates that the distribution of the mite among brood cells is not random but rather aggregated (31, 33). Aggregation, which has also been observed under laboratory conditions (21), could indeed favor exogamy [genetic diversity] and may have an adaptive value for the mite. However, it is not known whether this phenomenon is related to an aggregation pheromone or to the higher attractiveness of certain larvae either to the mite or to the nurse bees carrying the mite to the brood cell. Moreover, other findings, resulting from different statistical approaches, are contradictory and do not support the aggregation hypothesis (72, 106).

F. Nazzi, Y. Le Conte Ecology of Varroa destructor, the major ectoparasite of the Western Honey Bee, Apis mellifera
Annu Rev Entomol (2015)     http://dx.doi.org/10.1146/annurev-ento-010715-023731

Bill Hesbach 
Cheshire CT

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