Calliphoridae (commonly known as blow-flies, carrion flies, bluebottles, greenbottles, or cluster flies) are insects in the Order Diptera, family Calliphoridae.
The family is known to be nonmonophyletic, but much remains disputed regarding proper treatment of the constituent units, some of which are occasionally accorded family status (e.g., Bengaliidae, Helicoboscidae, Polleniidae, Rhiniidae).
The name blow-fly comes from an older English term for meat that had eggs laid on it, which was said to be fly blown. The first known association of the term “blow” with flies appears in the plays William Shakespeare: Love’s Labour’s Lost, The Tempest, and Antony and Cleopatra.
Description:
Characteristics:
Calliphoridae adults are commonly shiny with metallic colouring, often with blue, green, or black thoraxes and abdomen. Antennae are 3-segmented, aristate. The arista are plumose the entire length, and the second antennal segment is distinctly grooved. Members of Calliphoridae have vein Rs 2-branched, frontal suture present, and well-developed calypters.
The characteristics and arrangement of hairs are used to tell the difference between members of this family. All blow-flies have bristles located on the meron. Having two notopleural bristles and hindmost posthumeral bristle located lateral to pre-sutural bristle are characteristics to look for when identifying this family.
The thorax has the continuous dorsal suture across the middle, along with well-defined posterior calli. The post-scutellum is absent or weakly developed. The costa is unbroken and the sub-costa apparent on the insect.
Development:
Most species of blowflies studied thus far are anautogenous; a female requires a substantial amount of protein to develop mature eggs within her ovaries (about 800 µg per pair of ovaries in Phormia regina). The current theory is that females visit carrion both for protein and egg laying, but this remains to be proven.
Blow-fly eggs, usually yellowish or white in colour, are approximately 1.5 mm x 0.4 mm, and, when laid, look like rice balls. While the female blow-fly typically lays 150-200 eggs per batch, she is usually iteroparous, laying around 2,000 eggs during the course of her life.
The sex ratio of blowfly eggs is usually 50:50, but one interesting exception is currently documented in the literature. Females from two species of the genus Chrysomya (C. rufifacies and C. albiceps) are either arrhenogenic (laying only male offspring) or thelygenic (laying only female offspring).
Hatching from an egg to the first larval stage takes about 8 hours to one day. Larvae have three stages of development (called instars); each stage is separated by a moulting event. The instars are separable by examining the posterior spiracles, or openings to the breathing system .
The larvae use proteolytic enzymes in their excreta (as well as mechanical grinding by mouth hooks) to break down proteins on the livestock or corpse they are feeding on. Blowflies are poikilothermic, which is to say that the rate at which they grow and develop is highly dependent on temperature and species.
Under room temperature (about 20 degrees Celsius) the black blowfly Phormia regina can go from egg to pupa in 150–266 hours (6 to 11 days). When the third stage is complete the pupa will leave the corpse and burrow into the ground, emerging as an adult 7 to 14 days later.
Food sources:
Adult blow-flies are occasional pollinators, being attracted to flowers with a strong odor resembling rotting meat, such as the American pawpaw or Dead Horse Arum. There is little doubt that these flies use nectar as a source of carbohydrates to fuel flight, but just how and when this happens is unknown.
One study has been done to prove that the visual stimulus a blow-fly receives from its compound eyes is what is responsible for causing its legs to extend from their flight position and allow it to land on any surface.
Larvae of most species are scavengers of carrion and dung and most likely constitute the majority of the maggots found in such material, although it is not uncommon for them to be found in close associate with other dipterous larvae from the families Sarcophagidae, Muscidae, and many other acalyptrate muscoid flies.
Diversity:
There are 1,100 known species of blowflies, with 228 species in the Neotropics, and a large number of species in Africa and Southern Europe. The most common area to find Calliphoridae species are in the countries of India, Japan, Central America, and Southern United States.
The typical habitat for blow-flies are temperate to tropical areas that provide a layer of loose, damp soil and litter where larvae may thrive and pupate.
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