Blow fly puparium. Phormia regina is a very important species in medico-criminal entomology, an area in forensic entomology which involves the calling upon of entomologists to aid with arthropod evidence in criminal investigations. Blow flies are usually the first insects to colonize a body after death. Phormia regina adults and larvae are attracted to the body because during decomposition, the remains go through rapid physical, biological, and chemical changes. If a corpse is found, the early stages of diptera present may be used in determining the post mortem interval by reverse estimation of the time it would take for eggs to have been deposited and larvae to have developed to the stage they were collected, while taking into account environmental factors. Each deposits about 250 eggs in the natural openings of the body and open wounds. The eggs hatch into first-stage maggots within 24 hours. These feed and then molt into second-stage maggots, which feed for several hours, and then molt into third-stage maggots. Masses of third-stage maggots may produce heat, which can raise the temperature around them more than 10簞 C. After more feeding, the third-stage maggots move away from the body and metamorphize into adult flies.