Jim, I see what you mean. I was thinking that I need to have the feedback from the drone pupae itself. I guess you are right, one can figure out a correlation between the actual brood temp and the the bi-metal thermostat and perhaps fiddle with thickness of the wire on the bi-metal (in case that it shuts off before the drone pupae are cooked or, conversely, too late) -- providing that the bi-metal can be custom-made perhaps. perhaps there could even be sensors that "read" out how much brood is already sealed inside the hive on this frame. I remember Tom Webster used to have a royal jelly monitor inside queen cells that can assess the quantity of food with some electric terminals... Zachary http://www.mitezapper.com