Fly (Blowflies) Calliphoridae family

Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Diptera
Suborder: Brachycera
Infraorder: Muscomorpha
Subsection: Calyptratae
Superfamily: Oestroidea
Family: Calliphoridae
Subfamilies:
      Auchmeromyiinae
      Calliphorinae
      Chrysomyinae
      Luciliinae
      Melanomyinae
      Polleniinae
Species: 1100 are known. 52 species in New Zealand
Common names: Blowflies, Blow-flies, Carrion flies, Bluebottles, Greenbottles, or Cluster Flies

Calliphorid flies are generally found everywhere and are mostly stout, large to moderate in size and are often shiny with metallic colouring, with blue, green, or black thoraces and abdomens. They fly mainly by day.
The adults are often attracted to sweet liquids such as nectar from flowers. They also feed on the liquid products of organic decomposition, which provide the proteins essential to the female for egg maturation within her ovaries. Most species breed in carrion but some species are of significant veterinary importance, causing the cutaneous myiasis (skin infestation by the maggots) of livestock known as `fly strike'. The name blowfly comes from an older English term for meat that had eggs laid on it, which was said to be flyblown.

The larvae (maggots) of most species are scavengers of dead animals, excrement, and occasionally living flesh and most likely constitute the majority of the maggots found in such material. The typical habitats for blow flies are temperate to tropical areas that provide a layer of loose, damp soil and litter where larvae can pupate.

Lucilia species (Golden blowfly)
http://www.terrain.net.nz/friends-of-te-henui-group/local-flies/fly-lucilia-spp.html