Being annual colonies, housekeeping is not high on the list of must do tasks in a bumblebee colony. Various "stored product pests" are the rule rather than the exception in most colonies be they wild, collected or lab cultured. Using old birds nests, especially in bird houses, and animal nests is the rule of thumb with one group of species often referred to as "combers" if I recall correctly. I have found them to be the easier type to culture and are the ones most often used under commercial conditions. Their colonies appear to be bigger and longer "lived" on average than other types. You need to take recommendations in context, sterilizing before use or reuse is more slanted towards situations under commercial conditions where you are starting hundreds of colonies under close quarters and/or enclosed conditions. Bumblebee colonies for greenhouse pollination is a big bucks affair. They are what has made the greenhouse tomato a going concern as a case in point. :::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: -- Visit www.honeybeeworld.com/BEE-L for rules, FAQ and other info --- ::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::