Sarcophaga bullata

Sarcophaga bullata, or the grey flesh fly, is a species of fly belonging to the family Sarcophagidae. It varies in size from small to large, 8 to 17 millimeters in length and is very similar in appearance and behavior to a closely related species, Sarcophaga haemorrhoidalis. S. bullata is a common scavenger species in the Eastern United States, but is found throughout the Nearctic region. Identification down to the species level in the family Sarcophagidae is notably difficult and relies primarily on the male genitalia. Though limited information is available regarding S. bullata, it has gained increasing recognition in the field of forensic entomology as a forensically-relevant fly species, as it may be among the first species to colonize human remains. In these instances, recovered maggots may be analyzed for post-mortem interval (PMI) estimations, which may be used as evidence in courts of law. Current studies regarding S. bullata have revealed a maternal effect operating in these flies that prevents pupal diapause under certain environmental conditions, which is an important factor to be considered during forensic analyses. Classification of the species has also proved difficult, as it has for much of the family Sarcophagidae. C.H. Murran, for instance, included Sarcophagidae in a larger family, Metopidae, that added some Muscidae and some Tachinidae. Most, however, consider S. bullata to be a member of the subfamily Sarcophaginae within Sarcophagidae. Beyond that, the family can be split into tribes before defining genus. S. bullata is widely accepted to be a member of the genus Sarcophaga, but it is also included by some in a subgenus, Neobellieria. Sarcophaga bullata is approximately 8 to 17 millimeters in length. The head is colored ashen grey, and the arista (hair) of the antenna is plumose (feather-like) only at the base, unlike a Calliphorid fly, whose arista is plumose the entire length. The eyes of S. bullata are bright red in color, and are rather widely separated on the top of the head. On the genae, or cheeks, are long bristly hairs. Two orbital bristles are present on the females, while the orbital bristles are absent on the males. Present on the thorax are three contrasting black and grey longitudinal stripes; these stripes do not continue onto the abdomen. Sarcophaga have 4, rather than the normal 2 or 3, notopleural bristles, and 3 sternopleural bristles. A prominent row of black bristles (setae) can be found on each side of the thorax, just above the base of the hind leg and just under the base of the wing. These two sets of bristles are what differentiate Sarcophagidae from Muscidae. S. bullata lacks the postscutellum, the large swelling underneath the scutellum of the thorax, which distinguishes the flesh fly from Tachinid. S. bullata have black legs, translucent wings, and do not have a costal spine. The abdomen is grey and slender, with a median black stripe. It is checkered with a shifting pattern and black reflecting spots.Sarcophaga most resemble the blow fly, but never have metallic colored abdomens. There are no bristles on the middle tibia of the fly, but the hind tibia has fringed or long hairs irregularly placed. The genitalia is located on the end of the abdomen and in the males is a bright red color. The genitalia is one of the main identification characteristics used to identify the different genera of Sarcophagidae. The life cycle of Sarcophaga bullata is characterized by holometabolous development, though, like all known sarcophagids, the species is larviparous, meaning that the egg develops internally and females then give birth to first-instar larvae. This must be accounted for when using the species in forensic work to calculate a post-mortem interval. Though not much has been written specifically on the reproductive cycle of S. bullata, Sarcophagids are thought to be consistent within the family when it comes to life cycle. The eggs themselves are about 0.5 to 3.5 millimeters in length and 0.12 to 0.8 millimeters in width, though hatching occurs within the uterus just before the deposition of larvae. Sarcophagidae larvae are white or pale yellow, cylindrical, and tapered anteriorly. All segments beyond the first have anterior and posterior bands of hairs. The mandibles are usually strong and curved, resembling a hook. Posterior spiracles are sunken in, which is a characteristic that can be used to distinguish between flesh fly and blow fly larvae. Larvae are most often found in decaying animal matter.