> (3) Offspring mortality is linked to environmental factors, e.g. the
> combined effect of high temperature and low humidity. This hypothesis
> is the most likely, since the offspring mortality cycles mirror
> changes in the external environmental conditions.

Way back when there were several posts on using heat to combat Varroa. 
the technique was used in Russia. I found this in the archives and 
part is quoted below. The post was titled, "Heating Varroa".

> The other device demonstrated at the meeting is meant for treating
> swarms in summer or colonies in winter. You move the cluster to a net
> cage. The net cage is placed in a vented oven at 49 degrees Celsius
> (120.2 deg. F) for 15 min. Then the bees is put back into the hive. The
> man that build this system claims that the low relative moisture content in
> winter air combined with the heating is responsible for the death of the
> varroa mites. Critics say that these bees will die from nosema afterwards.
> The method should have been used for many years in Russia, but
> literature is scarce -- references would be very much appreciated!

So you have another independent source hypothesizing about heat and 
low humidity as a Varroa control, and may have done so.

Bill Truesdell
Bath, Maine

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