These flies are a common pest on cattle farms. They prefer to lay their eggs directly into rich organic matter such as cattle manure or fermenting plant material such as silage. Breeding areas can therefore be found areas where manure accumulates or is disposed, especially where this manure remains moist for several days.

Flies can also breed in spoiled, fermenting grain-based feed. Although these flies can travel several kilometers under favorable conditions, they generally remain in the vicinity of their breeding sites. House fly problems are therefore usually home grown rather than imported. Also included in this group is the lesser house fly (Fannia canicularis).

Since both adult flies and larvae have relatively distinct habitats it is possible to direct control action against both the adult and larval stages. Adult flies can be controlled with wall sprays and baits. Larval control involves certain physical measures as well as the application of larvicides to breeding sites.

Biology

The adult flies we see represent only a small percentage of the fly population present in a dairy farm or feedlot. The adult is merely the final stage in a series of juvenile stages. If control measures are only directed against adult flies it is difficult to get a handle on the problem.

Adult flies probably only live for about a week under field conditions but in this time a female fly can lay some 500 eggs. Eggs are laid directly onto manure which accumulates in stables, where they hatch within a day or so.

Breeding conditions can also be found around buildings in places where manure has accumulated and remains moist for several days. The larvae (or maggots) have no legs and no distinct head. They feed on organic matter in manure throughout three larval stages, or instars. Between each instar they shed their old skin and produce a new one made of chitin. The manure has to have a high moisture content as larvae do not survive in dry manure.

Up to 10,000 flies can mature in just 1 kg of manure!

When fully grown the maggot will search for a drier location where it turns into a pupa. Such places are usually at the edge of the manure beds. Pupae are small, barrel shaped capsules about the size of a grain of rice.

A few days later an adult fly will emerge from the pupa. And the life cycle continues.