Just in case anyone takes what I write seriously, I should correct several 
things in my recent post and add a few more cogitations:

> ... I have noticed that the technique enters into the results... it is a 
> little tricky making sure the mites do not get filtered by the dead bees.

It also seems that some bees are larger and fuzzier than others, altering 
the filtration effect.  For that matter, bee size seems to vary from day to 
day.

>> I also find it rather difficult counting mites looking up into the 
>> liquid, and rather slow trying to shake and count samples in the beeyard.

We use ethanol and it is clear and clean, so seeing mites is not all that 
difficult, and I sometimes tip the jar on its side so the mites spread out 
and are easier to count.  When using coloured washer fluid and wearing a 
veil on an overcast day, counting is much harder, especially if there are 
more than a few mites.  I prefer to work on sunny days without a veil.

If the number is low, counting is easy, but when you get over a dozen or so, 
the job gets harder, and depending on why you are counting mites, in such a 
case, just marking the sample TMTC (Too many to count) is often adequate.

At that point, if a number of samples are showing much more than a few specs 
in the jar and counting is a real chore, most beekeepers should -- IMO --  
stop shaking bees and start working on a solution because, unless the 
counting is part of a study, the exact results are pretty much academic.

Personally, I have to count them carefully because that is my job and the 
results are part of a study, but in the real world, one glance should tell 
the tale.  No careful counting is required, really, but I understand that it 
is nice to have good numbers when discussing the problem with others.

> We're dealing with big commercial guys with an average of about five 
> thousand hives each ...

I always re-read my articles to ponder if I wrote clearly and if I misspoke, 
so I thought about this and realised that if this were true, we would be 
sampling almost twice as many hives as there are in Alberta.  Moreover, not 
everyone participates in the programme, so let's amend that to 2,400 as a 
rough estimate.  If anyone cares, I can get the exact average number.

> ... IMO, it all comes down to a binary output (worry or don't worry) that 
> is not much affected by an error of even 20%, and, used properly, this 
> tool is accurate within 15%, 95 times out of 100. (95% of all statistics 
> are made up on the spot).

It seems some people take me seriously from time to time, so I hope everyone 
realises I am joking when I say "95 times out of 100".  That is a standard 
phrase and implies statistical rigour in the preceding number that may or 
may not be there.  In this case, it definitely is not.  I think it is a fair 
estimate, but Medhat will give you the real numbers if it is important.  The 
accuracy varies with the actual mite density and is only a probability. 
There are outliers as well.

Medhat shows a scatter chart in his presentations showing a comparison of 
field test done by real people in real situations with the same samples 
re-worked in the lab with mites and bees counted carefully and accurately, 
and the field accuracy is plenty good, especially for practical purposes 
like determining probability of survival and whether and when to treat.

When we worry about accuracy down to the last mite, we must consider, too 
that the samples are only *assumed* to be representative of the hive 
population, and there is bound to be some subjectivity and operator error. 
To know the real number, one would have to kill the hive and then 
painstakingly find and count every mite.

That brings me to my latest puzzle and I am about to reveal my ignorance 
more fully.  This must be a very elementary question to some writers on this 
list, but I am realising that I just do not know. Maybe someone can save me 
a few hours and the lives of 300 young bees...

I have started looking at bees more closely again now that I realise that I 
need reading glasses to really see them and the mites.  I assumed the mites 
are obvious on the bees, but am finding they are not as obvious as I had 
assumed.  When I was younger, I could see bees and larvae quite well up 
close, but now I find that I need good light and reading glasses to see the 
detail.

Anyhow, our discussions about phoretic varroa have me wondering.  I see 
mites perched on bees from time to time, but when I sample 300 bees, they 
often do not have any obvious "riders", even when 10 or more mites show up 
in the shake, so where exactly are the mites on the bees?  I seem to recall 
seeing pictures of mites showing between segments, but do not see this when 
I pick up and examine bees casually.

I am sure I have that information and maybe pictures in one of my many 
books, but I am wondering whether, if I chilled some bees (so they were easy 
to examine) and examined them very carefully, then warmed them up shook them 
in alcohol, would I find mites I cannot spot by the examination?  If so, 
where exactly are they hiding? 

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