I think I brought this up once before, but I was wondering if anybody knows if this has any potential to work. Many types of birds will pick-up ants and rub them all over their feathers to encourage the ants to spray formic acid on them. It is deadly to mites. They just drop off dead. Most birds like to dust themselves to gain the benefits of ants spraying them. What if you could place formic acid on something that the bees have to brush against on their way into the hive? I don't think that formic acid has any effect on other insects.