Calliphoridae

• Calliphorinae
• Chrysomyiinae

Blow-flies (also frequently spelled blow flies or blowflies) are members of the family Calliphoridae of flies (Diptera). Flies in this family are often metallic in appearance.

Some members of this family are known as bluebottles, cluster-flies, greenbottles, and in Australia, as blue-arsed flies. The name blow-fly comes from the fact that recently deceased corpses would swell up from bacterial decomposition in the intestinal tract, causing them to become bloated, or "fly-blown". Blow-flies are usually the first insect to come in contact with a dead animal.

The family is divided into subfamilies, the Calliphorinae, and the Chrysomyiinae, which between them contain about 23 genera.

Blowflies have caught the interest of researchers in a variety of fields, although the large body of literature on calliphorids has been concentrated on solving the problem of myaisis in livestock. It is estimated that the sheep blowfly Lucilia cuprina causes the Australian sheep industry over $170 million a year in losses. While much of the biology of these flies has been studied in the laboratory, the natural life history of the blowflies remains a largely untapped body of research.

Adult blow-flies are occasional pollinators, being attracted to flowers with a strong odor resembling rotting meat, such as the American pawpaw. There is little doubt that these flies utilize nectar as a source of carbohydrates to fuel flight, but just how and when this happens is unknown.

Most species of blowflies studied thus far are anautogenous; females require 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 are approximately 1.5 mm x 0.4 mm, are yellowish or white, 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.

Hatching from an egg to the first larval stage takes about 12 hours to one day. Larvae have three stages of development (called instars); each stage is separated by a molting event. 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 30 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 14 days later.

Since development is highly predictable if the ambient temperature is known, blow-flies are considered a valuable tool in forensic science. Traditional estimations of time since death (namely rigor mortis and algor mortis) are generally unreliable after 72 hours and often entomologists are the only officials capable of generating an accurate approximate time interval. The specialized discipline related to this practice is known as forensic entomology.

Blowfly maggots have also been used successfully in the treatment of badly infected wounds: see maggot therapy.