It has been suggested that bees to-day are less susceptible to infestation with the mite than in the days of the Isle of Wight disease (Anderson, 1930); the resistant bees were thought to have been selected out by the epidemics.  

The mortality of infested bees was only slightly greater than that of non-infested bees and became evident only after the bees had been in prolonged unfavourable circumstances. 

A great deal of the infestation found by Rennie et al. may have been due to poor weather; they made repeated references to the poor season and the lack of surplus honey in the colonies in the year that they made most of their investigations.

It seems very likely that the infested colonies were distressed by other unidentified causes, additional to infestation with the mite: such colonies, prevented by some reason from foraging normally or from producing a normal amount of brood might, if lightly infested, have developed their high proportion of infested bees in the ways discussed above; the infestation would then have been the effect of distress, not the cause, although when it became heavy, it might have had a supplementary effect.

Bailey, L. (1958). The epidemiology of the infestation of the honeybee, Apis mellifera L., by the mite Acarapis woodi Rennie and the mortality of infested bees. Parasitology, 48(3-4), 493-506.

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