>
> >30,000 mites? Am I missing something?  A big colony would be 30k bees


30,000 bees is not a large colony.  When I count, I typically count
2000-2500 bees per frame.  At 2000/frame, a 30,000-bee hive would cover
only 15 frames.  My colonies get much larger than that.


> >at a 25% level the hive is done, spotty brood and DWV has wreaked havoc
> for weeks already


Not what I see at all.  When I run hives returning from almonds without
splitting them, many hit 25 mites/100 bees by July if I don't treat them.
I typically start seeing spotty brood at around 15-20% infestation of adult
bees.  And those colonies are big--often with 20 frames of bees.

>
> A November collapse for most of the country results in Zero emigration.


OK, let's say a collapse on October 1--shortly after the colony exceeded
the typical threshold for collaspe of 25% of the brood infested.  A mite
wash of 1/2 cup of bees would hit 50 mites, and there would be approx.
10,000 mites in the hive at that time.

>
> As mentioned both your math cases assume 1/2 the mites manage to move to
> another hive,
>

The 1/2 was a WAG.  As the infestation rate climbs, the mites start to
prefer to ride on older bees rather than younger bees.  The big question is
to what degree those bees drift, rather than simply fly off to die.
Robbing is another story, as the remaining mites emerge with the last of
the brood, and hop onto the robbers.

We clearly need much more hard data on the degree of drifting.  What I
observe in my high-mite test yards is that the infestation rate of low-mite
colonies climbs at a much faster rate than the mites could possibly
reproduce, thus leading me to the conclusion that those colonies picked up
a large number of mites via drifting bees.

-- 
Randy Oliver
Grass Valley, CA
www.ScientificBeekeeping.com

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