mite problem in dogfood!

i was just reading the dog treats thread and someone mentioned an allergy to dogfood mites. can someone tell me about them? when we moved to our new house we naturally brought our dogfood container. we have never had a bug problem before, but after living here a few months i kept feeling something like fine grit on the top of the lid. i finally took the lid outside and looked at it and yuck!, there were about a million tiny, almost microscopic white things-very much like spider mites crawling slowly all over it. well, you KNOW there was a major cleaning then!!! LOL these are not flour weevils or anything even close-tiny, white spidermites. now when i bring the dogfood home it stays in the freezer, not fridge. i have a big glass cannister where i keep a weeks supply, so i pour it into that. then i have to leave the lid off until all the moisture evaporates or it would get moldy. i know this is gross, but i would really like to know what they are. they didn't spread to anything else in the kitchen. believe me, i checked! thanks, debi