What sort of Flies do we have in New Zealand

The Housefly (Musca domestica), is a fly of the suborder Cyclorrhapha. It is the most common of all domestic flies, accounting for about 91% of all flies in human habitations, and indeed one of the most widely distributed insects, found all over the world; it is considered a pest that can carry serious diseases. The adults are 8–12 mm long. Their thorax is gray, with four longitudinal dark lines on the back. The whole body is covered with hair-like projections. The females are slightly larger than the males, and have a much larger space between their red compound eyes. The mass of pupae can range from about 8 to 20 mg under different conditions. 

The Lesser house fly (Fannia canicularis), is somewhat smaller (3.5–6 millimetres) than the common housefly. It is best known for its habit of entering buildings and circling near the center of rooms. It is slender, and the median vein in the wing is straight. Larvae feed on all manner of decaying organic matter, including carrion. It is the most common vector of myiasis within the Fanniidae.

Cluster flies are the genus Pollenia in the blowfly family Calliphoridae. Unlike more familiar blowflies such as the bluebottle genus Phormia, they do not present a health hazard because they do not lay eggs in human food. They are strictly parasitic on earthworms; the females lay their eggs near earthworm burrows, and the larvae then infest the worms. However, the flies are a nuisance because when the adults emerge in the late summer or autumn they enter houses to hibernate, often in large numbers; they are difficult to eradicate because they favour inaccessible spaces such as roof and wall cavities. They are often seen on windows of little-used rooms. They are also sometimes known as attic flies.

Blow-flies (​Calliphoridae) are insects in the Order Diptera, family Calliphoridae with 1,100 known species. The family is known to be non-monophyletic, but much remains disputed regarding proper treatment of the constituent units, some of which are occasionally accorded family status (e.g., Bengaliidae, Helicoboscidae, Polleniidae, Rhiniidae). Adults may vector pathogens of diseases such as dysentery. Flies, most commonly Calliphoridae, have frequently been associated with disease transmission in humans and animals as well as myiasis. Studies and research have linked Calliphora and Lucilia to vectors of causal agents of bacterial infections. These larvae, commonly seen on decaying bodies, feed on carrion while the adults can be necrophagous or vegetative. During the process of decay, microorganisms (e.g. mycobacterium) may be released through the body. Flies arrive at the scene and lay their eggs. The larvae begin eating and breaking down the corpse simultaneously ingesting these organisms which is the first step of one transmission route.

Vinegar flies (Drosophila) are a genus of small flies, belonging to the family Drosophilidae, whose members are often called "fruit flies" or (less frequently) pomace flies, vinegar flies, or wine flies, a reference to the characteristic of many species to linger around overripe or rotting fruit. They should not be confused with the Tephritidae, a related family, which are also called fruit flies (sometimes referred to as "true fruit flies"); tephritids feed primarily on unripe or ripe fruit, with many species being regarded as destructive agricultural pests.