Submitted to: Experimental and Applied Acarology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/1/2005
Publication Date: 12/1/2005
Citation: Villa, J.D., Danka, R.G. 2005. Caste, sex and strain of honey bees (apis mellifera) affect infestation with tracheal mites (acarapis woodi). Experimental and Applied Acarology 37(3-4):157-164
Interpretive Summary: Tracheal mites are parasites of honey bees which continue to damage or kill colonies in the United States. Worker honey bees from strains having resistance usually have very low infestations of these mites. Resistance is based chiefly on the ability of individual worker bees to effectively groom mites off themselves as mites are moving from bee to bee. This research involved comparisons of the infestations of queens and drones, together with those of workers from colonies selected for resistance and for susceptibility. Measurements were made by exposing the three types of bees of the two genetic origins to these mites. As expected, workers from resistant colonies were less infested than workers from susceptible colonies. However, drones from resistant colonies were more highly infested than those from susceptible colonies. Queens of the two origins were not different in their infestation. Drones and queens appear to lack the ability to groom mites off their bodies. Therefore, beekeepers should avoid exposing drones and queens to infestation by tracheal mites. Genetic improvement of resistance to tracheal mites is not going to benefit from the theoretically more effective use of selection through drones.
Technical Abstract: Worker honey bees from genetic stocks selected for being resistant (R) or susceptible (S) to tracheal mites typically show large differences in infestation in field colonies and in bioassays that involve controlled exposure to infested bees. We used bioassays to compare the propensity for tracheal mites to infest queens, drones and workers from R and S colonies. Workers from R colonies had significantly lower infestations than workers from S colonies as expected, but queens and drones did not express this pattern of resistance. Infestation did not differ between young R and S queens when queens were simultaneously confined in infested colonies or when caged individually with groups of 5-20 workers from infested colonies. When young drones and workers from both types of colonies were caged with infested workers, R workers had lower infestation than S workers, but R drones had greater infestations than S drones. Removal of one mesothoracic leg from R and S workers resulted in increased in infestation of the tracheae on the treated side, but excising legs did not affect infestation in drones. This suggests that differences in infestation between R and S workers, but not drones, are largely determined by their ability to remove mites through autogrooming. Beekeepers propagating queens and drones in environments that promote tracheal mite infestation need to minimize the exposure of young drones and queens to infestation even if the queens and drones are derived from stocks with resistant workers. The use of selection on hemizygous drones is unlikely to bring about rapid genetic improvement for tracheal mite resistance.