Flies in New Zealand

  • Flies are insects in the order Diptera, meaning they only have 2 wings – a key distinguishing feature
  • Diptera are one of the largest orders containing an estimated 1 million species, including houseflies, flesh flies and drain flies, but also blowflies, fruit flies, horse flies, hover flies, mosquitoes and midges
  • The various species have sucking, piercing and sucking or sponge-like mouthparts, all adapted to a liquid diet
  • Many fly species have important ecological roles, but others are seen as pests and transmit diseases to humans

Types of Fly



Flesh Flies

Vinegar fly or fermentation fly

Vinegar Fly

Drain Fly

Only a few species of the million or so fly species are seen as significant pests.

  • Some such as the housefly, tsetse fly and mosquitoes are seen as serious health threats to humans.
  • Others are pests of agriculture (fruit flies) and animal husbandry (flesh flies).
  • Some are just nuisance species, which are undesirable in the home and in the food manufacturing and hospitality industries, such as the vinegar fly and drain fly.

More information on the diseases that houseflies carry.

The key method to identify a fly is by looking at the number of wings. Bees and wasps have two pairs of wings, flies only have 2 wings (one pair). Instead of the second pair of wings, flies have halteres, small club like structures which are used to provide information on orientation when flying.

It is not possible to cover the key identifying features of all the species, so we will focus on 4 of the key species:

  • Housefly – had 4 dark lines on the thorax
  • Flesh fly – has 3 dark lines on the thorax
  • Vinegar fly – a small, light brown /  yellow fly (3-4 mm long), with red eyes
  • Drain fly – a small, hairy fly, with moth like features (but only 2 wings!), around 4-5mm long

How can you tell the difference between houseflies and flesh flies?

Flies undergo a complete metamorphosis (change in body form) – egg, larvae (or maggot), pupa and adult.

Flesh flies are slightly different as they lay hatched or hatching maggots directing on rotting meat or on the open wounds of animals (from which they get their name).

The speed of the life-cycle is dependent on the species, temperature and available food, but typically the life-cycle is completed in 1-2 weeks under favourable conditions, with adults only living for 2-4 weeks.

Understanding where the various pest species live and eat provides important information about identifying the source of a fly problem and eradicating the infestation.


Houseflies are one of the “filth” flies, which get their name from their habit of living in and around faeces and garbage. Both larvae and adults feed on any organic material. When the larvae are ready to pupate, they will crawl away from these feeding areas which tend to be moist to drier areas where they build their pupa.

Flesh flies

Flesh flies, as they name suggests, feed on rotting meat, carcasses and sometimes the wounds of live animals. Around homes and business, if you have a problem with flesh flies, it is likely there is a decaying carcass in the roof void or sub-floor.

Vinegar flies

Vinegar flies are sometimes called fruit flies, as they are seen flying around fruit. However, it’s their other name – fermentation fly – which provides the clue – they are attracted to rotting fruit, but also beer and wine.

Drain flies

Drain flies as their name suggests hang around drains, so are common in toilets and bathrooms. They breed in the organic matter than accumulates in drains. However, they don’t need much material in which to lay eggs and the larvae develop, so organic material in cracks and crevices can also provide a suitable breeding site.


There are three key steps in getting on top a fly problem:

  1. Find and eliminate breeding sites
  2. Kill any adults
  3. Prevent new adults entering the building

The first step is key – finding and eliminating the breeding site, which will be the source of the infestation. This is where the skill of a professional pest manager can be very beneficial.

For houseflies, the breeding site is normally outside in manure or garbage.

For flesh flies, the source is generally a rotting animal carcass (possum, bird or rat) in the roof void or sub-floor.

For vinegar flies there will be some rotten fruit of vegetables somewhere, maybe at the back of a cupboard or under an appliance. Sometimes in may be a spill of a fruit beverage. It is necessary to look in all cracks and crevices.

Drain flies breed in the organic material than collects in drains.

Once the breeding site has been identified and removed or cleaned away, it’s simply a question of carrying out a spray treatment to target any adults.


Preventing a fly problem generally comes down to preventing the development of suitable breeding sites, which generally comes down to good hygiene practices.

For houseflies make sure garbage is place in bags and sealed, and placed in bins with tight fitting lids. Garbage bins can also be sprayed with insecticide. Pick up any dog and cat poo in the yard and avoid using chicken manure as fertilizers.

For drain flies, get into the practice of regularly cleaning all drains (at least once a month).

The use of fly traps or fly zappers can be useful if you need to keep housefly problems to a minimum, which is clearly very important in the food manufacturing and hospitality industries.

More fly problem prevention tips.

Our pest control library has a range of articles on pest control flies and fly research.

Our article on small pest flies is a good starting point.