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This attractive fly is called the Broad Centurian (Chloromyia formosa). It is a sexually dimorphic species where both male and female have a shiny green thorax but the female has a blue-green abdomen, sometimes with a violet sheen, and the male has a bronze abdomen. This is a female. Look closely and you may notice the eyes are covered in dense black hairs, which helps to distinguish it from the similar Sargus solderflies.
The larvae feed on decaying organic matter.