im guessing you have your mealworms in bran, oatmeal or some such..??? if so its pests coming and hatching from them and id sift/sort out the mealworms as small as can and pupa and beetles, then keep in dry compost type situation and dump grain ect stuff out to chickens or in regular compost. it seems odd, but mealworms are actually dermastid type beetles and can and will eat any food thrown in by them from greens veggies and fruit, to carrion (side note they are used by some taxidermists and museums for cleaning bones ect..), and actually do a lot better in just plain soil and compost great (found this out by accident years ago, and always kept them around until just recently gave away to enthusist to give him a good head start in breeding them). the small grain pest ect will go away after enough moisture is provided, as they dont need the totally dry environment thats said b those who sell them for profit, and found it actually retards their production, just dont let the soil get too wet. the parasites come in the grain but attack the mealworms for moisture and can kill them by clogging air vents and sapping moisture, and will make them all want to stay on surface out of tiny buggy substrate. ive had no trouble with pests in soil to the mealies. also they will breed well when provided with paper eggcrates or paper cup holders on top of soil for beetles to breed and lay on, were the larva worms cannot so easily eat the eggs and then you may have way to many. lol also forgot that potatoes seem to be bad food especially in the grain type setup and seem to promote the worst smell and parasites/pests for some reason, and i suggest carrots or leafy greans. either or good luck and hope you do well with them!