That looks like a drone pupae.
What I do to minimize drone brood is use all properly fitted wax foundation in the brood box. If the bees mess it up, resulting in large areas of drone comb, I cycle them out & give them fresh foundation. You basically want all your brood frames to contain around 95% worker comb. That will give the colony a strong population of workers. The workers chase beetles incessantly, non stop until they find somewhere to hide. Then the bees wont let them out, stopping them from laying eggs. Drones wont do that because they are not defenders of the hive.
A decent honey spill can disrupt that process because while bees are busy cleaning up the mess, the beetles that are normally contained can break free, allowing them to do damage & lay eggs. The discarded brood is probably from the vicinity of the damage caused by the beetles. Which is one possibility.