Spilomyia alcimus

Wasp-Mimic Flower Fly
Spilomyia alcimus

Wasp-mimic Flower Fly Spilomyia alcimus female on Hoptree June 02, 2007 Wheatley, Ontario.
Wasp-mimic Flower Fly Spilomyia alcimus female on Hoptree June 02, 2007 Wheatley, Ontario.

Identification:
Head: Face projecting; yellow with a longitudinal dark stripe down middle. Eyes very large, striped yellow and black, with some black spots on the yellow. Top of head black, wider on female. Mouth reddish-brown.
On female, the yellow with dark stripe extends above antenna.

Wasp-mimic Flower Fly Spilomyia alcimus male on Wild White Rose June 13, 2008 Wheatley, Ontario.
Wasp-mimic Flower Fly Spilomyia alcimus male on Wild White Rose June 13, 2008 Wheatley, Ontario.

On male, there is a small amount of lighter yellow above antenna, but no dark stripe and eyes are close together.
Antenna: Yellowish, last joint more reddish. Bristle (arista) 3 times as long as antenna.
Thorax: Black. Segment 1 (scutum) with two large yellow spots on each side at base. Wide yellow stripe on each side, curving to near centre. Two small yellow curved stripes at center of segment end. Segment 2 (scutellum) yellow. Thorax sides have two large oblong, yellow spots, one below the other, almost touching. Another small yellow spot under wing base.
Wings: Half clear, outer half brown with brown narrowing toward tips. Another shorter brown streak on base half of the clear part of wings. Veins slightly darker. Halteres yellow.

Wasp-mimic Flower Fly Spilomyia alcimus male on Wild White Rose June 13, 2008 Wheatley, Ontario.
Wasp-mimic Flower Fly Spilomyia alcimus male on Wild White Rose June 13, 2008 Wheatley, Ontario.

Legs: Thighs (femora) light yellowish-orange. Brown streak on underside of hind thigh. Shins (tibiae): front shin dark, mid and hind shins light yellow. Front feet dark, mid and hind feet yellowish-orange.
Abdomen: Yellowish-orange. Base of 1st segment dark, with yellow extending up segment side edges. All other segments have a thin brown stripe, interrupted at center, across middle of each segment. Underside yellow with dark longitudinal stripe down middle of all segments, dark stripe wider on female.

Wasp-mimic Flower Fly Spilomyia alcimus female on Virginia Mountain Mint, July 21, 2017. Leamington, Ontario.
Wasp-mimic Flower Fly Spilomyia alcimus female on Virginia Mountain Mint, July 21, 2017. Leamington, Ontario.

Similar Species: Spilomyia longicornis is almost identical, except abdomen is dark with thin yellow stripes.

Size: Male 14 to 16 mm, female 18 mm

Habitat: Woods and forest edges.

Food: Adults feed on nectar from flowering plants, shrubs and trees: Virginia Mountain Mint, Queen Anne’s Lace; Dogwood, Sumac, Hop and Linden (Basswood) trees.

Flight Time: Mid-June to August.

Life Cycle: Unknown. One report of 5 larvae living in treehole of live White Oak Quercus alba in Michigan by Maier, Ent. Soc Washington, 1982.

Comments: One found at Point Pelee per Guelph University. Also one at Niagara Falls and one in Guelph per Canadensys. Recorded in Wheatley 2006 to 2009, and 2014. Leamington 2017.
In Ontario, this flower fly is most similar to the queen wasp of German Yellowjackets (Hornets) Vespula germanica. These flower flies wave their black front legs to imitate the Yellowjacket antenna.

For information on synonyms, references and type specimens see next page

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