HortFACT
Identification
Adults are dull black flies with slightly smoky wings and rather elongate, tapering bodies. The female is about 9.5 mm long and may be readily distinguished from the male by the dull red area between the eyes. The male is smaller (about 6.5 mm long) but has larger eyes.
Eggs are very small and would riot normally be seen.
Larvae [maggots] are creamy white when small or after moulting, but greyish and dull at other times. They have a maximum length of 8 mm and are sluggish in movement, leathery, distinctly segmented, pointed bluntly towards the black apex of the mouthparts, and rounded at the posterior end. Larvae are usually located around the area of maximum root development of grasses other pasture and crop plants, and weeds. They are not likely to be confused with the larvae of other common soil insects except perhaps wireworms (click-beetle larvae), which are much more active, creamy in colour, and have a distinct head.
Pupae are brownish and similar to the larvae in shape, although somewhat smaller. Pupation occurs at the soil surface.
Host plants
The total range of food plants is not yet known, but larvae have been found feeding on practically all Pasture plants, including weeds. Australian soldier fly occurs also on tomatoes, cereals, cucurbits, shrubs, rockery plants of most types, and most agricultural and horticultural crops. The larvae grow faster on grasses such as kikuyu, ryegrass, phalaris, tall fescue and cocksfoot, than on paspalum and white clover.
Damage
Damage is most extensive and insidious in pasture, particularly rye grass. Evidence of damage is not noticeable in the field until production drops and grass growth becomes obviously arrested X. Later, pasture composition shows imbalance, tending towards paspalum and weed dominance in coastal areas and often towards clover or weed dominance in cooler areas. Populations of larvae may rise to about 10,000 per square metre.
Considerable damage may be done to grain or other crops, if these are sown after cultivation of infected pasture.
Distribution
Australian soldier fly occurs from just north of Auckland through coastal areas to beyond Opotiki on the east coast, south through the Waikato to Te Kuiti, and inland to Rotorua. It is also recorded from Gisborne. The range could in the future probably extend throughout grassland areas of the North Island and into warmer areas of the South Island.
Life cycle
| Egg |  |
| Larvae | |
| Pupae | |
| Adult | |
| Month | |
| Note: Coloured bars indicate periods of peak activity in each of the life cycle stages | |
Whereas in Australia this pest has only one main flight period (in May), in New Zealand flight periods are more erratic; there is usually a minor peak about November or early December and a major peak in March or April, with intervening irregular flights.
Mating takes place soon after emergence, and females lay eggs in crevices in the soil or in shelter beside the bases of plants. Eggs hatch in 2-3 weeks, and young larvae Immediately begin feeding on plant roots. A number of larval instars occur, with little difference between them apart from size. On average the complete larval stage lasts 18 months to 2 years, so larvae are in the soil at all times of the year. At pupation larvae darken, assume a vertical position with the head at the soil surface, and lose their mobility.
B.B. GIVEN