Diptera, true flies in the Calliphoridae family

Calliphoridae, blow flies, bluebottles, greenbottles.

These are commonly known as bluebottles, greenbottles and blowflies. There are over 1500 species in the world and 38 British species. The adults range in length from 5 - 15 mm. Most of the larvae feed on carrion and decaying matter, but a few species are parasites. The adult mouthparts are similar to those of Musca domestica. Many of the adults are a metallic green or blue, and have bristles all over their body.

Many in this family are attracted to rotting flesh, and can detect the smell of decay within minutes after death. Because most of the larvae feed on vertebrate carrion, species in this family have become very important in forensic entomology as the rates of development of the larvae of different species can indicate the time of death. Anglers also use blowfly larvae as bait.

Maggot therapy

Blowfly larvae are used in medicine in "maggot therapy" where they are used to clean up wounds. The greenbottle Lucilia sericata is the most commonly used species. Specially reared therapeutic maggots are placed for 48 hours on wounds in a dressing that is really a cage. A patient may have to undergo one or more of these cycles before the wound is clean and able to heal spontaneously or is ready for a skin graft.

This kind of therapy has been used to treat pressure ulcers, venous ulcers, foot ulcers in diabetics, burns, traumatic wounds, and other wounds that are not healing. The therapy is simple, safe and has a low cost.

The genus Calliphora contains the bluebottles, and the genus Lucilia contains the greenbottles.

Calliphora vomitoria, common bluebottle, adult

Above is a preserved specimen of the common bluebottle, Calliphora vomitoria, and below a close-up photograph and drawing of the head. It breeds throughout the year. Adults have a bluish metallic abdomen. Note the huge eyes, the two sausage-shaped things are part of the aristate antennae, adult length is 8 - 14 mm, wingspan 15 - 25 mm. It is usually the females that we find in our houses, as they search for meat or fish on which to lay their eggs. The males tend to stay outside basking in the sun and drinking nectar from flowers.

Calliphora vomitoria, bluebottle fly adult head

Calliphorida head

The female lays her eggs on carcasses, open wounds or rotting meat for her larva to feed on. The eggs are creamy white, and 1.5 mm long, and can hatch within a day. A female can lay up to 600 eggs in her life time. The pupa is a dull red/brown.

Calliphoridae larva, blowfly larva

Below is the pupa of a blowfly. The bars on the ruler are at 1 mm intervals. The pupa has a hard skin. When the adult fly is ready to emerge from the pupa the fly inflates a small bladder on the top if its head. This bladder presses against a weak point in the top of the pupa causing a circular rupture in its wall which pops upwards to form a lid allowing the adult flu to escape.

Blow fly pupa

Taste discrimination in blowflies

Adult flies taste with their feet, and on the last tarsal segment they have gustatory bristles and taste hairs. These hairs have a pore at the end into which a stimulus can enter to reach the sensory cells.

There are five sensory cells in each hair; one mechanoreceptor which detects bending, two which respond to salts (one to anions the other to cations), one responds to sugar, and one to water.

The feet perform preliminary tasting of substances. If these substances are acceptable as food or water then the fly will extend its proboscis. This preliminary tasting prevents the fly from tasting harmful substances with its proboscis as the fly doesn't actually take in any food until it has passed the chemical tasting of its tarsal hairs and also the hairs around the edge of the labellum, which work in the same way as the tarsal taste hairs.

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