Egg - About 1 mm long, the elongate-oval egg is pale yellow or cream colored when newly laid but darkens with time. Each egg mass contains about 500 eggs.
Larva - The black soldier fly larva is plump, slightly flattened, with a tiny, yellowish to black head. The skin is tough and leathery. Creamy white and about 1.8 mm long when newly hatched, the larva develops through six instars, the last of which is reddish-brown. The mature larva is about 18 mm long and 6 mm wide, although some individuals may be as long as 27 mm.
Puparium - The motile pupa develops within the darkened skin of the last larval instar (puparium). The pupa is about one-third the length of the puparium.
Feeding Habits - Soldier fly larvae are scavengers and thrive on many kinds of decaying organic matter, including carrion, manure, plant refuse and the waste products of beehives. Adults commonly frequent flowers of the daisy and carrot families.
Damage - Though they may be a nuisance, soldier flies do not bite and are not known to transmit any diseases. Occasionally larvae accidentally infest the intestinal tract of man or animals. Fortunately, such cases are not common and the maggots pose little real threat. In fact, this species has the beneficial effect of rendering the breeding media less suitable for the production of house flies.
Life History - Larvae of black solder flies develop through the winter in decaying organic matter. Development slows greatly in extremely cold weather. Depending on temperature and other environmental conditions, pupation occurs in spring and lasts from 9 days to 5 months. Therefore, some adults appear as early as April but many do not emerge until late summer. The larvae seek sheltered, dry locations to pupate.
Newly emerged soldier flies mate in flight. Soon afterwards females begin to deposit egg masses near edges of decaying organic matter. Eggs incubate 4 days to 3 weeks before hatching.
Few life history studies on this insect have been done in North America, but in New Zealand larvae have been found to require a minimum of 31 days to develop to the 6th instar. In this stage, the winter is passed.