> I'd rather that Medhat answer, but the technique appears to wash off 
> virtually all the mites.  Hard to tell, since you would have to inspect 
> each and every washed bee with a lens to determine.

After we field test, the samples go to the lab for a follow-up analysis 
which includes counting the bees, since the number of bees is important for 
establishing percent.

Speaking off the top of my head, I understand that the 60-second field shake 
usually shows up about 9 out of 10 mites +/-1.  There is some variability, 
though, because it seems that mites sometimes are harder to shake off than 
others and technique varies.  If it is not done right, the bees in the upper 
half can act as a filter and hold back mites, so some practice is necessary. 
A slight swirling motion seems to work best when draining the alcohol down 
at the end of shaking to keep the screen clear of dead bees which might hang 
up some mites..

> I hate to speak for Medhat, but I believe that he found that 20 shakes was 
> adequate.

It may be, but in my experience, it depends how fresh the sample is.  It 
takes a few minutes for the mites to let go, I think.  I also often shake 
three times (a long shake and several short ones) and take the highest 
number. 

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