They lay their eggs in open orifices. The eggs hatch. The resultant larvae feed, grow, and pupate before becoming adults. When using maggots to determine the time since death, the forensic scientist must identify the maggot's species. The different species of flies have different reproductive time intervals.
Species differ from one another in appearance during their growth stages.
So the maggots are removed from the corpse and cultivated. When the adult fly eventually appears and the species of adult fly is recognized, the timing data from its life cycle can be applied precisely. There is no evidence that Dr. Peerwani, his staff, Dr. Ubelaker, or Dr. Owsley were interested in verifying time since death by examining the remains for pupal cases. After all, the murderers of these Branch Davidians were still free, and could be apprehended by the law. The common housefly, which is easily identified by its three black thoracic stripes, is primarily an indoor animal.