Yup, I got mites too. I ended up taking some pupa, beetles and worms, rinsing them in a strainer with cool water for an awful long time, the putting them in a new batch of (in my case, corn meal). I'm just starting to get babies after the entire winter of things not looking so well. The rest, I fed to my chickens. (mites won't hurt the chickens). I was afraid, recently, that I was getting mites again, and took my box outside. It looked a bit dusty in there... not sure if I had mites or not again, but outside in my neck of the woods, is very dry. Usually we have under 15 percent humidity, and there have been no more signs of mites. I've decided that I'll keep them outside from now on, at least until winter, when I'll have to figure something out???
Good luck with your mealies!