Spilomyia longicornis

Distinguished from similar syrphid flies by the combination of: dark anterior wing margin contrasting with clearer remainder; forelegs with black distal portions moved in antenna-like display; and overall larger size compared to many flower flies. Separated from actual vespid wasps by single pair of wings (Diptera), lack of constricted wasp waist, and typical fly head structure with large compound eyes.

Adults occur near flowers producing pollen and nectar. Larval habitat consists of rot holes—damp, rotting cavities in live trees. Almost any tree species can develop suitable rot holes, though frequency varies by tree type.

Eastern North America, east of the Rocky Mountains. Documented in multiple states including Illinois and Vermont.

Adults feed exclusively on pollen and nectar from flowers. Females require pollen nitrogenous nutrients for vitellogenesis (yolk deposition and reproductive tissue development). Nectar provides energy for hovering flight. Larval diet unknown but inferred to involve decomposition products in rot holes.

Larvae develop in rot holes of living trees, where they find food and protection in damp decomposing wood. Adults emerge and spend majority of time at flowers for feeding and mating. Females require pollen for reproductive development.

Exhibits tripartite mimicry of vespid wasps including Vespula vulgaris: (1) Visual—color pattern and dark anterior wing margins; (2) Behavioral—rests on hind four legs while raising and moving forelegs above head in antenna-like motions; when threatened, bends abdomen in mock-stinging posture and may pulse abdomen up and down mimicking wasp abdomen expansion; (3) Auditory—produces altered buzzing frequency when threatened, similar to some Hymenoptera. Males have been observed mate-seeking near flowers.

Adult pollinator providing ecosystem services to flowering plants. Larvae contribute to nutrient cycling in forest ecosystems through processing of decaying wood in tree cavities.

Beneficial pollinator with no sting despite wasp-like appearance. Documented in entomological collections including century-old specimens, contributing to understanding of historical ranges and biodiversity patterns.

• Vespula vulgaris and other vespid waspsS. longicornis is a Batesian mimic; distinguished by single wing pair, lack of wasp waist, and fly morphology
• Other Spilomyia speciesShare genus-level mimicry traits but differ in specific leg coloration, wing pattern, and geographic range
• Other syrphid wasp-mimicsDistinguished by combination of dark anterior wing margin, specific foreleg color pattern, and size

• pollinator
• mimicry
• Batesian mimicry
• forest
• rot hole
• flower visitor

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• GBIF taxonomy match
• iNaturalist taxon
• NCBI Taxonomy
• Catalogue of Life
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