Chrysomya rufifacies

Chrysomya rufifacies is a species belonging to the blow fly family, Calliphoridae, and is most significant in the field of forensic entomology due to its use in establishing or altering post mortem intervals. The common name for the species is the hairy maggot blow fly, and it belongs to the genus Chrysomya, which is commonly referred to as the Old World screwworms. This genus includes other species such as Chrysomya putoria and Chrysomya bezziana, which are agents of myiasis. C. rufifacies prefers very warm weather and has a relatively short lifecycle. It is widely distributed geographically and prefers to colonize large carcasses over small ones. The species commonly has a greenish metallic appearance and is important medically, economically, and forensically. Chrysomya rufifacies was first described by the French entomologist Macquart. Its specific epithet is derived from the Latin words rufus 'reddish' and facies 'face'. Some taxonomists believe C. rufifacies is conspecific with Chrysomya albiceps due to biological, ecological, distributional, and morphological similarities. The larvae of both species are very difficult to distinguish, and only a minor difference exists between the imagos. A prostigmatic bristle is said to be present in C. albiceps and absent in C. rufifacies, but it is not present in all C. albicepes or it is very reduced, so this character is unreliable. The status of C. rufifacies is not completely clear, and its relation to C. albiceps has not been fully determined. The hairy maggot blow fly can be readily identified by examining for a shiny metallic blue-green color, a pale genal dilation, and a vestiture of the anterior thoracic spiracle that is pale in color. The mature adult is about 6–12 millimetres (0.24–0.47 in) in length. The use of a microscope allows the investigator to identify setae on the fly's meron, a greater ampulla with stiff erect setae, black first and second abdominal tergites, and a black posterior margin of the third and fourth abdominal tergites. These features are characteristic of the genus Chrysomya. The differentiation between C. megacephala and C. rufifacies is accomplished by observing the anterior thoracic spiracle color. C. rufifacies has a pale or white anterior thoracic spiracle, while C. megacephala has a dark brown or dark orange anterior thoracic spiracle. Also, C. rufifacies contains three faint pronotal (pronotum) thoracic stripes which are not readilyvisible. The larvae of C. rufifacies are very easily identified with sharp, fleshy tubercles running down their bodies, and the mature larva is about 14 mm (0.55 in) in length with a dirty yellowish color; hence the common name, hairy maggot blow fly. The peritreme of the posterior spiracle is very wide with a narrow gap that contains forked edges; the slits are short and wide, almost filling the plate. Knowledge of the lifecycle of C. rufifacies is crucial in determining the post mortem interval for applications related to medicocriminal entomology. Accurate developmental and successional data for the species can significantly aid in legal investigations. C. rufifacies is especially important in these determinations due to its highly predictable developmental time and low degree of variation in larval development. The lifecycle of C. rufifacies is characterized by holometabolous development, consisting of egg, larva, pupa, and adult stages. The entire lifecycle takes 190 to 598 hours depending on temperature. The female lays an average of 210 eggs and a recorded maximum of 368 eggs near fresh corpses and often during daylight hours. After the eggs have been laid, the first-instar larva of the insect emerges from the egg about 26 hours later at a temperature of 29 °C. A total of three larval instars are involved in the lifecycle of the species, and the entire larval development stage takes 2.5 days at a temperature of 29 °C. The larvae are capable of regulating their body temperature by moving to a different position in the maggot mass to maintain a preferred developmental temperature. The maximal preferential temperature for the larvae of C. rufifacies is 35.1 °C. The developmental time of the species is highly dependent upon temperature due to the cold-blooded nature of insects and the number of accumulated degree days. Any variability in developmental times can also be due to different rearing temperatures under different conditions such as varying humidity, rearing media, and larval density. A prepupal stage is often present and characterized by larval dispersion and migration away from the food source in search of a pupation site. The body length of the larva decreases during this stage in preparation for pupation. If the larvae are restricted from movement and not allowed to disperse during the prepupal stage, a 24-hour delay in pupation will be observed. Thus, in medicocriminal investigations, if a corpse is wrapped and causes restriction of maggot migration, altered developmental times should be considered. The prepupal stage takes 1.5 days and the pupal stage takes 3 days at a temperature of 29 °C. Pupation usually occurs near the soil surface or near decaying flesh, and the skin of the larvae hardens to form a dark brown puparium or outer casing. Adults emerge after pupation and mate 3–7 days after emergence in summer, and 9–10 days after emergence in autumn. Adults are capable of living for 23–30 days, and oviposition occurs about 5 days after mating.