Hi Bill, See: http://www.algonet.se/~beeman/index-f.html Click onto research - varroa. You will be able to read about Formic and Oxalic. Whilst this thread is running: How much metal corrosion is caused by these two acids in bee hives? - I have seen metal entrances that have a fair bit of damage after formic acid treatment. Peter :::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: -- Visit www.honeybeeworld.com/BEE-L for rules, FAQ and other info --- ::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::