The immature stages of the necrophagous fly, Prochyliza nigrimana: comparison with Piophila casei and medicolegal considerations (Diptera: Piophilidae)

Flies of family Piophilidae have been recorded as major pests in the food industry, as agents of human myiasis and typically associated with carcasses in advanced stages of decay, being thus important in forensic entomology. Despite that the cosmopolitan species Piophila casei is the most cited in entomological studies, many other piophilid species develop on both carrion and animal products from the food industry. One of those species is Prochyliza nigrimana, widely distributed throughout the Holarctic and Neotropical regions. In this study, the morphological features of the immature stages of P. nigrimana are described for the first time and compared with those of P. casei. The third-instar larvae and puparium of P. nigrimana are significantly shorter than those of P. casei; the contrary pattern is observed in egg length. The number and arrangement of the lobes of anterior spiracles, which had been used as a distinctive character of P. casei in some keys, are the same in both species. Morphological features of the cephaloskeleton (such as the general shape and the distance between the tips and the base of the mouth hooks/base of the mouth hooks ratio), the arrangement of anal segment in third-instar larvae and the appearance of the ventral creeping welts in the puparium are the main characters allowing for identification of both species.