If the bee parts are parts of white pupa that have been chewed off the developing pupa, this means the queen is laying brood and the brood is infested with varroa mites. The bees know there is a mite reproducing in the cell and they chew away the pupa to remove the foundress mite and her young. This is called Varroa Sensitive Hygiene (VSH) and is desirable trait to have in your bees.
If the parts you see are things like legs, wings, or other parts of adult bees it is as has already been posted, normal for a colony.