adult is a robust tawny fly averaging 9-12mm long, although undersized
specimens are frequently seen. The eyes of the female are separated by
about 1-2mm, whereas on the
they adjoin one another. Adults can be seen at all times of the year,
but are most common in spring, summer, and autumn.
- The eggs, which are
laid in small clusters, are creamy white and about 1mm long. The
young larvae (maggots) are grayish-white and segmented. There are
three instars (larval stages), and the fully grown maggot may be
12-15mm long. The
reddish-brown, barrel-shaped pupae can be found a few centimeters
below the surface of the ground.
The larvae of these flies are normally found on carrion, but the
female fly will sometimes lay her eggs or larvae on the fleece of
live sheep. A sheep or ox carcass will support many thousands of
The blowflies cause little damage, as they are normally scavengers
that are the first in a chain of insects that clean up carcasses.
However, when they attack a living animal (usually a sheep), severe
damage or death of the animal may occur. The female fly is attracted
to sheep when the wool is wet or damp. The odor of feces, urine, or
bacterial straining will also attract flies. The
adult fly is a nuisance in households or shops where fresh or
uncooked meat is present, and unprotected meats are likely to be fly struck
(have eggs laid on them). Adults are also attracted by the Odor of
some vegetables, such as cooked cabbage. Females are usually looking
for a protein meal pa prerequisite for egg production) or somewhere
to lay their eggs or larvae.
- Distribution: The
brown blowfly is a native of Australasia, and has been known in New
Zealand since the beginning of European colonization. It is found
throughout the country, from sea level to above the bush line. It is
closely related and very similar in appearance to another species of
blowfly commonly found in forest areas.
- The adult female is
viviparous (gives birth to larvae) in the warm summer months, but in
cooler weather lays eggs. When eggs are laid, they hatch in a few
hours, and the larvae reach full size and stop feeding after about
3-4 days. The fully grown larvae migrates away from the food source,
and burrows underground a few centimeters to pupate. Pupation takes
2-3 days, and the pupal stage lasts a further 8-10 days. Flies are
not sexually mature until several days after emergence, and after
mating the female will then commence depositing up to about 200 live
larvae or eggs on a suitable substrate, over a period of 2-3 weeks.
Depending on ambient temperature, female flies may live for several
weeks after egg laying is complete. The entire life cycle from egg
to egg takes 3-5 weeks during summer, but considerably longer in the
winter months. Pupae are known to over winter in the soil, and it
seems likely that larvae could do the same, as this is known to
occur in other species. When ready to emerge, the young adult forces
its way out of the end of the pupal case, finds its way to the
surface of the ground, and expands its wings, which soon harden off.
Females fly off in search of a protein source. Little is known about
the male but it probably lives as long as the female, and once it
has fertilized one female, will probably seek others. Adult
flies will shelter in trees and buildings during winter,
occasionally flying on warm, sunny days, but rarely laying eggs.
Four to five generations a year can be expected.