Hygienic behavior the bees will uncap and remove the pupae that is infested with the mite. Genetics the bees will remove the larva just after the egg hatches so day 4 or 5 from being laid. mark an area of solid eggs and chedk it in 2, 3,& 4, days time and shortly after the eggs hatch some of the larva is removed Genetics. If not and it is all caped in 7 to 9 days and them some of the cells are opened it could be hygienic behavior. But it may not be mites but other diseases or pathogens also that are causing the bees to remove the larva.