At the capitalist bug farm, mice were always getting into our waxworms, because they buildings were poorly built, they used poorly-sealed kitty litter boxes to grow the waxworms in, and the racks easily allowed the mice to climb up (partly because of escaped-worm cocoons on them).
We'd see them running across the main floor all the time. It was very common to open up a box after 6 weeks and see a litter of baby mice inside, and barely any waxworms. Maybe one out of every 50 was like that.