>
> >If this happens in every round of reproduction, simple math explains how
> these colonies can drop resident mite levels to negligible, and can even
> deal with small, and possibly large numbers of immigrating mites.


This certainly appears to be the case in Bond method selection, in which
any survivors must deal with the onslaught of mites from the collapsing
hives.  And I strongly suspect that it explains how certain colonies in a
yard of infested hives are able to consistently maintain low mite rates.

The study that Jose cited, re the apparent drifting of mites from Italian
to Russian hives, strongly supports the hypothesis of some sort of
"equalizing," of mite levels in an apiary continually takes place, and thus
certainly suggests that resistant colonies are also continually actively
removing mites or hampering mite reproduction.

Can anyone think of a study in which a yard was stocked with two groups of
colonies--one with low mite levels, and one with high?  We've done so
unscientifically when we've placed fresh nucs in yards with existing
colonies having higher mite levels, and got the impression that we got
major drift of mites into the nucs.  We now avoid this practice at all
cost.  But I'd like to see some hard data.

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

             ***********************************************
The BEE-L mailing list is powered by L-Soft's renowned
LISTSERV(R) list management software.  For more information, go to:
http://www.lsoft.com/LISTSERV-powered.html