"Do you think the dead varroas peak is delayed (when compared to OA vaporizing) because the OA solution is longer effective or is it because lethal effect is less acute ? Hervé Qc, Canada" (Guess) Maybe the bees give the oxalic/sugar solution from tong to tong to the other bees in the cluster, burn some off it, and store the rest direct above the nest, for later. ??? The acid is concentrated in the bee nest. With 1 gram vaporising the cloud divides trough the inside off the hive. It immediately crystallizes every ware. On the wood, frames and the outside off the bee cluster. The bees will cleanout the nest/cluster. The mites will die when there is contact with the crystals. Maybe this cleaning does not take much time. It could be a reason for the shorter time that mites will drop. These questions should be investigated. Hennie Kroese........ :::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: -- Visit www.honeybeeworld.com/BEE-L for rules, FAQ and other info --- ::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::