> The principle is called hyperthermi and two German devices for > treating frames of capped brood exist. These devices are called > "Borgstaedter Thermo Box" and "Apitherm" respectively. Varroa mites > are less tolerant to heat than the bees. <etc.> We have been getting some very interesting posts lately. This reminds me of a matter I brought up here a year or so ago and at some meetings - a question to which I have never received a good answer: a question about brood temperature in hives. I have wondered how variable the temperature in the centre of brood nests is between various hives and different strains of bees , and if it is related to the length of incubation of brood. What caused me to wonder was an experiment I did with a carefully calibrated high/low reading thermometer that showed the one hive I measured to maintain brood between 94.6 to 96.3 degrees F (average 95.5) through quite varying ambient temperatures. It seems to me that the literature I have read mentions 92 degrees F or so. Anyhow, I wonder if there have been experiments to examine this variability and relate it to the length of incubation (important in varroa resistance) or other characteristics. I don't imagine that a difference in brood temp of several degrees would affect varroa development negatively? Or would it? Regards Allen W. Allen Dick, Beekeeper VE6CFK RR#1, Swalwell, Alberta Canada T0M 1Y0 Internet:[log in to unmask] Honey. Bees, Art, & Futures <http://www.cuug.ab.ca:8001/~dicka>