Exaireta spinigera

The combination of four prominent yellow-tipped spines on the scutellum, black body with violet iridescence, and metallic abdominal sheen distinguishes this species from other soldier flies. The flattened larval body shape is characteristic of Stratiomyidae but not unique to this species. Adults may be confused with other dark Stratiomyidae, but the scutellar spines are distinctive.

Adults are black with violet undertones and shaded wings, measuring 14–16 mm in length. Males are smaller (9–10 mm body, 7–8 mm wings) than females (13–15 mm body, 11–12 mm wings). The abdomen is elongated and flattened with a metallic sheen. Four yellow-tipped spines protrude from the scutellum near the thorax. Antennae consist of three distinctive segments typical of Stratiomyidae. Larvae are flattened in shape.

Larvae inhabit decaying organic matter, particularly residential compost bins and other decomposing substrates. Adults are found hovering near decaying organic material and in residential gardens.

Native to Australia. Introduced to New Zealand (both North and South Islands, recorded from Pupuke to Papatowai), Hawaii (first recorded Honolulu 1890s), North America (first recorded Santa Barbara, California 1985), Europe (Italy, France, Belgium, Russia—Black Sea coast at Alder), and Russia.

Adults are diurnal with peak activity in autumn (March–May, peaking in April) and spring (September–December). Larvae have been observed in outdoor traps during winter months when Hermetia illucens is inactive.

Larvae are detritivores that consume decaying organic matter and food waste. Adults have been assumed to feed on pollen and nectar, though this has not been confirmed.

Eggs are laid directly into decaying organic substrate. Larvae pupate within the larval skin without external change. Larvae have been observed seeking drier locations to pupate when substrate conditions are too moist, though this behavior has not been directly observed. Specific details on mating behavior and complete life cycle duration are unknown.

Adults are diurnal. Larvae actively process decaying organic material and will relocate to drier conditions for pupation if substrate is excessively moist.

Larvae function as detritivores and decomposers in organic matter breakdown. The species serves as prey for various predators including the German wasp (Vespula germanica), black-headed jumping spider (Trite planiceps), praying mantis nymphs (Miomantis caffra), and the water beetle Dactylosternum abdominale.

Investigated as a bioconverter for food waste management, with larvae containing 38.6% crude protein even when fed 100% fruit and vegetable waste. Protein content and conversion efficiency decrease with low-protein feed, but the species remains active at cooler temperatures than Hermetia illucens, offering potential for year-round waste processing in temperate climates. Commonly encountered in residential compost bins.

• Hermetia illucensBoth are soldier flies used for food waste bioconversion, but Exaireta spinigera is active at cooler temperatures and has four scutellar spines versus the smooth scutellum of Hermetia illucens.

• compost-associated
• introduced species
• waste bioconversion
• detritivore
• diurnal

• BugGuide
• Wikipedia
• GBIF taxonomy match
• iNaturalist taxon
• NCBI Taxonomy
• Beyond Hermetia illucens: An investigation of the garden soldier fly Exaireta spinigera as a potential bioconverter of food waste