What i've heard is that the bees will sometimes panic and boil out of the hive when exposed to formic acid. Application and success rate is highly depending on temperature and air circulation within the hive. Maybe someone else with first hand experience can share some more information on this. I have been involved in extensive formic acid trials at a university over the past 3 years, involving hundreds of hives. I have never seen the bees boil out. In fact, I have never seen any harm done, aside from an occasional bee getting caught inside the plastic bag we used to contain the pad. We used a fiber board pad soaked with formic, placed above the frames inside a one inch deep rim. The cover and rim is duct taped in place to keep the fumes from escaping. But it is up to the bee industry to get formic on the market. I don't know what the status of that effort is these days. pb :::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: -- Visit www.honeybeeworld.com/BEE-L for rules, FAQ and other info --- ::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::