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
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© Tony Gunton