Calliphora loewi

The eggs of this genus are white, slightly curved, cylinder shaped and have blunt ends. Once the eggs hatch the larva stage begins. The three instars of the maggots have different characteristics. The first is less than 2 mm long and is a twelve segment skeleton with mouthparts present. The second instar has spines located on the dorsal side and has two posterior spiracle slits from which it breathes. During the third instar, the mouthparts are fully developed. The mouth-hook tooth becomes longer, and the maggot now has three posterior spiracles.[3]

When the third-instar larva has finished growing (12–18 mm), it leaves the corpse and burrows into the ground where it develops into a hardened, capsule-like pupa. The brown/black pupa retains a maggot like appearance with outlines of its spiracles and skin, except now it is sclerotized. While encased as a pupa, it is unable to feed and is immobile.[3]

It takes around 14 days (at a temperature of 70 degrees Fahrenheit) before the pupa emerges as an adult fly. The newly adult fly is pale in color with a soft body and wings. As it matures, the fly expands its wings, and the body hardens and changes color. A mature C. loewi is approximately 6–14 mm in length. The fly then mates and will travel several miles to lay its eggs, and the cycle repeats.[3]

Forensic entomology is the study of arthropods and their connection to the courts of law. The family Calliphoridae is very important in forensic entomology. The genus Calliphora also has a very distinct life cycle so based on the different stages that can be found on a corpse; therefore an accurate post mortem interval can be determined.[4]

Upon finding blowflies and or their larvae on a corpse, it is extremely important to accurately identify the correct species. For example, a semi- rounded sclerite lying behind the mouth-hook of blowfly larvae exists only in C. loewi and C. vomitoria.[5] Since both of these species of Calliphoridae tend to be found in rural areas, an entomologist can use these characteristics to determine a region or habitat where the victim died.

Entomologists can use SDF (spiracle distance factor) values when identifying between Calliphora sp. SDF is calculated by dividing the distance between the spiracles by the greatest diameter of one spiracle.[5] Since the greatest diameter of one spiracle tends to remain constant for each species, SDF values are very useful. To tell the difference between C. loewi and C. vomitoria, the SDF for C. vomitoria decreases (the spiracles come closer together) when the puparium transitions between the 2nd and 3rd instars. The SDF for C. loewi however remains constant (the spiracles maintain their distance between).[5]

In the epidemiological sense, blowflies are of concern due to being possible mechanical vectors of disease.[6] Blowfly breeding and feeding hosts tend to be decomposing animals and dung, which are covered with bacteria that consequentially come in contact with the fly. Lab studies have shown that blowflies coming in contact with agar have produced cultures that contain pathogens. Although C. loewi does breed in carrion and possibly in human feces, it remains uncertain whether it carries or transmits disease.

They are also very important ecologically because they are decomposers. Blowflies are not only attracted to decomposing hosts but to some plants as well. C. loewi and other blowflies have been observed to be attracted to Phallus impudicus, the stinkhorn fungus, which tends to smell like carrion.[2] The Stapelia flower, which smells like carrion and emits heat like that of decomposition, also attracts blowflies. The flower causes females to oviposit (deposit eggs from ovipositor) but it does not support past the 1st instars. Some other plants do support larvae through full development.[2]