Blow Fly (or Bluebottle)

Calliphoridae

Appearance Adults are 6-16mm in length with a metallic blue, green, or black body. They have sponging mouthparts and antennae. Larva are are eyeless, legless, tapered from large, rounded rear segment to head, which is a pair of dark hooks. They are 9-22mm long when mature. The eggs are 1.5 mm in length and are pale yellow to white in colour. Habits Feeds on meat, small animal and bird carcasses, excrement, decaying vegetation and garbage. Breeds in mostly meat derived substances, sometimes cheese.

Lifecycle

A female blow-fly will typically lay 150-200 eggs per batch and around 2,000 eggs during the course of her life. Eggs are laid on material which larvae will eat (preferably meat). Hatching from an egg to the first larval stage takes about 8 hours to one day. Larvae may feed on the surface and then burrow into less decayed material underneath. Larvae usually take from 7 to 12 days to mature before moving away from the carcass to pupate. The entire life cycle usually requires between 10 and 25 days.

Disease

Flies regurgitate and excrete wherever they come to rest and thereby transmit disease organisms. Pathogenic organisms are picked up by flies from garbage, sewage and other sources of filth, and then transferred on their mouthparts, through their vomitus, feces and contaminated external body parts to human and animal food.

More than 65 pathogens are associated with the blow fly which may cause disease in humans alone.

Blow flies are known to carry bacteria and viruses that cause conditions such as diarrhoea, typhoid fever (Eberthella typhosa), bacillary dysentery (Shigella dysentariae), tuberculosis, anthrax ophthalmia and infantile diarrhoea, as well as parasitic worms, cholera (Vibrio comma), poliomyelitis, food poisoning, yaws, tularaemia, and eye infections. They have also been suspected as vectors of the viral agent that causes poliomyelitis. Food preparation and storage areas can be contaminated by the flies themselves or their faeces.