[11][12] Most of the body of Melangyna novaezelandiae is coloured metallic black with a green yellow tint.

[16] The eggs of the flies are laid in close proximity to aphid colonies, which the larvae feed on once they hatch.

[20][21] Because of this diet, the larvae have been considered for use as biocontrol agents in New Zealand to manage aphids and other pests that damage crops in agricultural habitats.

[3][2] In contrast to the diet of the larvae, the adults of M. novaezelandiae are herbivorous and feed on pollen to develop their reproductive systems, and on nectar for energy, which may make them a useful pollinator.

[16] A previous study that linked gut fullness with egg production has suggested that this finding provides evidence for pollen being used in reproductive system development.

[20] Melangyna novaezelandiae are known to be frequent pollinators in both agricultural and natural settings, including subalpine zones.

[19] In agricultural areas it was found that M. novaezelandiae was the second most common visitor of crop flowers, so may have an important role in pollination.

The finding of this study is that M. novaezelandiae had very low effectiveness (they transferred very little pollen between flowers) when compared to that of typical pollinators such as bumblebees and honey bees, which is likely to be attributed to its lack of specialization.

[25][26] One study found that M. novaezelandiae are most attracted to yellow colours, which may be an important cue in finding floral resources.