Phormia Regina - Forensic Importance

Forensic Importance

P. regina is a very important species in medicocriminal entomology, an area in forensic entomology which uses entomologists to aid with arthropod evidence in criminal investigations. This aspect of forensic science stresses using arthropod evidence in solving crimes, most often of a violent nature, using two ideal approaches. One approach takes into account the general succession of arthropod communities to aid in estimation of post mortem interval, and the second factors in environmental influences in the development of arthropods. With knowledge of the regional insect fauna and times of carrion colonization, the insect gathering associated with the remains can be analyzed to determine a window of time in which death took place. The time elapsed since death before a corpse is discovered, referred to as post mortem interval, or PMI, is critical for investigations. PMI relies on an entomologist’s ability to correlate the species or stage of development of arthropods, in this case P. regina, to an approximation of the elapsed period between a person's death and the discovery of his/her body.

Blow flies are usually the first insects to colonize a body, frequently within minutes after death. P. 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 dipterans present may be used in determining the PMI 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. The use of maggot age and development can give a date of death accurate to a day or less, and is used in the first few weeks after death. Blow flies will lay their eggs on the corpse, usually in a wound, if present, or in any of the natural orifices. Therefore, after a single blow fly generation has been completed, the time of death is determined using the first method, that of insect succession.

Research is being conducted to further perfect the dating of a PMI. One study suggests P. regina occasionally oviposits on carrion at night only when certain conditions are met. A similar study found a combination of artificial lighting, warm temperatures, and the onset of low-pressure atmospheric conditions encourages nocturnal oviposition in P. regina This knowledge of the effects of nocturnal temperatures on blow fly occurrence and oviposition behavior will lead to more accurate estimates of the PMI related to deaths, but more research is needed to assign a precise PMI.