Best time to see: Mar to end Nov

Key facts

A common fly often found in houses, belonging to a group known as blowflies that are believed to carry diseases

Thousands of their larvae, commonly known as maggots, can develop in a single carcass such as a rat or mouse

Commonest in summer but can also come out of hibernation and fly around on warm winter days

Recognition

A chunky-looking fly with metallic blue body, 10–14 mm long, red eyes and clear wings

Suck liquids from decaying matter and sometimes from berries with their mop-like mouthparts

Lifecycle

Females lay their eggs on decaying animals and faeces, attracted from considerable distances by the smell

The eggs hatch very quickly and the larvae burrow down into food, growing to full size within a week

The larvae leave the food and hide themselves away to pupate, the adult fly emerging a week or so later