Problems with mites: Sometimes a mealworm colony gets infested by grain mites (Acarus sp.) The mites may come from the mealworm supplier, in bran, or litter from poultry production, and may infest a colony that has been around for a long period of time. Excessive moisture + heat may be a contributor. They are prolific breeders (800 eggs/female) and can withstand temperatures of 0 degrees and still hatch when brought to room temperature. (Another species that can be a problem is the mold mite, Tyrophagus sp.)
The mites are tiny and round, whitish or tan in color, and have eight legs. They may cling to air holes and look like very fine sawdust. Mites can not fly.
If your colony does become infested, the mites will kill the larvae and adults. Destroy the colony (e.g. by freezing) and start over.
Not sure if they present any danger to your geckos (i.e. harboring parasites, irritating soft tissues), however my understanding of the article indicates that the mites will eventually destroy your mealworm colony anyways.
i have heard both...some say they are, others say they are not. i would destroy the colony and start over. just incase. is it really worth taking the chance on a few dollars worth of mealies? i have a colony started and it was really easy, i would not even think twice about it, i would start over. my animals health is worth so much more to me than even a few hundred dollars worth of feeders. i was keeping my mealies in the garage a while ago, the humidity caused the bedding to mold a little...i tossed out almost 2500 mealies without even thinking about it...it sucked, but 20 dollars worth of mealies is alot easier to replace than $3000.00 worth of leopard geckos!
There are many species of mites. Some of which may not parasitize your reptiles..but unless you know which type of mite it is I would simply start a worm colony again. Starting a new colony is easier than trying to treat all your reptiles and still have to restart your colony.