Sacrophaga

Distribution

''Sarcophaga bullata'' do not have wide natural distribution, and can only be found in the Nearctic region, or the part of North America that is north of Mexico. It is most common in the eastern and southern United States, but can be found from the western coast of the United States to Canada. ''S. bullata'' are commonly found in rural and urban environments, and it is commonly found in houses and indoor dwellings, especially during the summer months. The flies prefer the warmer months, and are active from May to September, with the majority of the activity in August and September.

Behavior

It is difficult to quantify the level and nature of "communication" that takes place among sarcophagid adults, though much is known about the role of pheromones in their reproductive physiologies. An experiment by Girard et al. in the 1970s demonstrated that ''S. bullata'' males release the sex pheromone hexanal, which was shown to attract over 65% of the females tested from over long distances. In studies regarding the social behavior of adult female sarcophagids larvipositing on animal remains, it has been suggested that adult females prefer to aggregate with other carrion flies and larviposit on carcasses that already have larvae present. A possible explanation for this selective preference is that an increased number of larvae results in a greater concentration of larval enzymatic secretions on the carrion, aiding in digestion. Sarcophagid larvae are also known to outcompete the larvae of other species and cause their extinction, and occasionally consume the smaller larvae present on animal remains.

Reproduction

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.

First instar:

First instar Sarcophagidae larvae are 0.5 to 5.0 millimeters long. The Sarcophaginae larvae, specifically, usually lack a labral sclerite, but in some cases it is present as a small, triangular plate located between the mandibles. The first segment is at times sclerotized on the dorsal surface, which can form a partial head capsule. The Sarcophaginae have a hypopharyngeal sclerite that is sometimes fused with the large tentoropharyngeal sclerite. They also lack an anterior spiracle, while the posterior spiracle usually consists of two lobes; rarely it may be bispinose.

Second instar:

Second instar larvae of the family Sarcophagidae are 4.0 to 10.0 millimeters long and closely resemble the third instar with the exception being that the posterior spiracle has only two openings.

Third instar:

Third instar larvae are 9.5 to 20 millimeters long. The mandibles are by now large and strongly curved. The dorsal cornu of the tentorpharyngeal sclerite appears incised due to a narrow apical window. The anterior spiracle is present with a short stalk that branches into several nodes, resembling a fan. The posterior spiracles now consist of three vertical slits within a sunken oval cavity. This cavity is surrounded by 8 to 12 tubercles, of which the dorsal ones are often sclerotized and have toothed processes, while the ventral tubercles are often covered in nipple-like projections. The anal opening is located in a fairly prominent posteroventral lobe that also has lateral tubercles.

Food

Adults of the family Sarcophagidae do not feed exclusively on carrion, despite the weighty implications of the name "flesh flies;" in fact, adult flies are frequently discovered feeding on sweet substances, such as sap and flower nectar. The flesh-eating character of the family refers primarily to sarcophagid maggots, which feed predominantly on carrion, exposed meat, and excrement. ''Sarcophaga bullata'', in addition to all species of the family Sarcophagidae, may be considered "specialized flies," a term coined by Baker and Baker to describe flies that feed on carrion and dung. Specialized flies have been proven capable of detecting and selectively favoring plant nectars with high amino acid concentrations. Extensive research has suggested that ''S. bullata'' females in particular favor amino acid-containing nectars as opposed to strictly sugary nectars, perhaps to secure healthy levels of protein for successful reproduction.

Adult flesh flies are attracted to animal remains in both early and late decomposition stages, and have been known to fly through even the most extreme weather conditions to reach carrion. Though adult flies of the family Calliphoridae typically arrive on human remains before those of Sarcophagidae, sarcophagid adults are unhindered by nearly all climatic conditions and may reach the carrion first during particularly stormy weather. Rather than laying eggs, ''S. bullata'' females retain fertilized eggs internally until they develop into first-instar larvae, which are then deposited directly onto carrion. As sarcophagid larvae are larger than those of most other colonizing flies, they often present significant larval competition for other species. Though sarcophagid larvae have been attributed to causing myiasis, a condition in which maggots feed on the tissue of a living human or animal, they are most commonly discovered feeding on animal remains. In the southeastern United States, species of the genus ''Sarcophaga'' are the principal flies found during the warm summer months on bodies located indoors, as females frequently enter dwellings to deposit its larvae.

In terms of relevance to decomposing tissue analysis, forensic entomologists must disregard an egg development time period in post-mortem interval calculations, as ''S. bullata'' and other sarcophagids deposit live larvae on carrion as opposed to eggs. For the same reason, fly egg masses discovered on human remains can be automatically ruled-out as belonging to sarcophagid flies.

Predators

''S. bullata'' has few, if any, specific natural predators due to their dispersal throughout the North American continent. Predators of ''S. bullata'' are carnivores, ranging from mammals and reptiles to carnivorous plants. However, a few primary predators are the ''Stagmomantis californica'' or the California Mantis, ''Catopsis berteroniana,'' ''Sceloporus undulatus'' or Eastern Fence Lizard, and the ''Perimyotis subflavus'' .