regarding mite sampling:

Two findings are clear from our work. First, mite-infested bees are not homogeneously distributed throughout the nest. There was significant comb-to-comb variation in infestation rates within colonies. Furthermore, infestation rates were about twice as high in the brood nest compared with the honey-storage area. 

This indicates that estimates of infestation rates on adult bees should be based on a sample of bees collected from several randomly selected combs with the contribution from each comb being proportional to the relative number of bees present on its surface. Foragers have lower infestation rates than nest bees, especially nurse bees

The second finding is that estimates based on the ether roll and estimates of the number of bees in a sample have a high correspondence with estimates based on the actual number of mites and bees present. The former estimates are considerably easier to obtain than the latter.

-- J. Econ. Entomol. 91(4): 851-863 (1998)

§

The main conclusions from our current results are that (1) 50% of Varroa mites are ready to transfer from a newly emerged worker (NEW) shortly after the bee emerges from its cell and (2) these mites have a higher propensity to transfer or move onto nurse and nurse-age bees rather than onto older bees or pollen foragers. 

For reproduction, we would expect the mites to move onto bees that will most likely bring them near, or into contact with, brood susceptible to infestation. However, for dispersal to another bee colony we would expect mites to move onto foragers, perhaps foragers from a different colony (a forager that drifted into the colony or a robbing bee). 

Among our test mites, two groups of mites appear to have been present that exhibited these two behavioral patterns, each perhaps in a different physiological state. This categorization presupposes that the mites can recognize some difference between bees.

-- Journal of lnsect Behavior, VoL 10, No. 2, 1997

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