Blowflies wear metallic armor over a carrion career
Blowflies, bluebottles and greenbottles make up the Calliphoridae, almost 1,900 known species of often shiny metallic flies. A single female may lay around 2,000 rice-grain eggs in her life, and her maggots, sold to anglers as gentles, dissolve flesh with enzymes in their own excreta.
Adults usually gleam blue, green or black, with three-segmented antennae whose bristle-like arista is feathery along its whole length. Specialists separate members by their bristles: every blowfly carries some on the meron, a plate low on the thorax, and a pair of notopleural bristles is another telltale sign. The family is polyphyletic, meaning it does not share a single common ancestor, and some groups within it are occasionally promoted to families of their own.
Most species studied need a big protein meal before their eggs can mature; in Phormia regina each pair of ovaries takes about 800 micrograms. Females are thought to visit carrion both to feed and to lay, though that remains unproven. Eggs measure roughly 1.5 by 0.4 mm and come in batches of 150 to 200. Two Chrysomya species break the usual even sex ratio, with each female producing only sons or only daughters.
Larvae hatch within about eight hours to a day and pass through three stages, told apart by their breathing openings. They grind with mouth hooks and digest protein outside their bodies. Because their development speed depends on temperature, Phormia regina at about 20 °C goes from egg to pupa in six to eleven days; the grown larva then burrows into soil and emerges as an adult one to two weeks later. That predictable clock is why the insects matter at crime scenes.
Adults also sip nectar and occasionally pollinate flowers that smell of rotting meat, such as the American pawpaw and dead horse arum. Spiders, beetles, frogs and birds eat them, and in Mexico's Chihuahuan desert a fungus, Furia vomitoriae, bursts through the abdomens of bluebottles and kills them.
Source: Calliphoridae
