COMMON NAME
Garden Soldier Fly
Order

Suborder

Family

Genus

Species

Alias
Diptera







Exaireta spinigera

Blue soldier fly

Description

The family name Stratiomyidae means “soldier fly like”. Adults are black and elongated, and look a bit like a mirid bug except that their wings don’t overlap. They do not have functional mouth parts, thus they do not eat waste or food themselves, feeding on nectar and pollen. They generally don’t go into houses, nor do they bite or transmit diseases. The larva are pale cream grubs with segmented bodies, becoming yellow as they grow. They can get to 25 mm in length. Just before pupating they become much darker, The eggs are cream or pale yellow, and laid in masses of as many as five hundred.

Adult size: 12 mm

Out and about

Larvae breed up in decaying organic matter, so I assume they are around all the time, perhaps just slowing down in cooler weather. This fly is native to Australia and is found mainly in temperate regions. It has been introduced into New Zealand, Hawaii, North America and Europe.

Reproduction and Life cycle

The eggs, as many as five hundred, are cream or pale yellow and laid near or in organic matter. After about 4 days the eggs hatch. Prior to pupating (at the sixth instar) the larvae become a dark brown colour and will leave the moist composting material in search of a dry sheltered area in which to pupate. At this stage their mouthparts change and become a stubby appendage that helps them to move around.

To deter

To control

Plants to repel

Plants to attract

Daisy / Carrot

Predators

Why they are Beneficial
Larvae feed on decaying plant or animal matter including carrion, manure and plant refuse. The soldier fly larvae are extremely efficient at converting organic waste into high quality nutrient rich fertilizer. Their frass (poo) is also a good fertilizer and in our case is mixed up with the compost. The larvae are often found in compost heaps, but unfortunately they do not cohabit with worms as they prefer a hotter and wetter environment. If present in the compost it probably indicates that the compost is not in the best condition for worms. However, our worm composting bath seems to be working for both- the worms tend to stay closer to the top where it is cooler and drier. We cover the compost with old hessian sacks and the worms are thriving just under these. At the pre-pupate stage the larvae are a good source of protein and are now farmed as feed for chickens. The larvae also store high levels of calcium which would be required when they pupate. The black soldier fly, Hermetia illucens , which is native to the Americas and found in tropical and temperate regions worldwide, is now farmed as the larvae are excellent protein feed for poultry. The larvae also store high levels of calcium which would be required when they pupate.
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