Wasp-mimic Flower Fly
Head: Black, long. Two very large or very small, raised yellow, oblong marks, almost touching each other, on top of back margin of head. Lower face yellow, not protruding, with mid black stripe, wider on female. Female with 2 tiny yellow marks above and one each side of antenna bases (total of 4), eyes wide apart; male has yellow inverted V-shape above antenna bases, eyes only slightly touching before simple eyes (ocelli).
Antenna: Brown, Y-shaped. Main ID: Antenna longer than head due to a long pedicle or post before antenna. Pedicle almost as long as first joint, base slightly yellowish. Tips sharply pointed.
Thorax: Black. Segment 1 (scutum) base has a yellow spot at each side. May appear as 4 spots, but 2 are actually on back of head. Another yellow spot near wing bases, sometimes absent. Faint gray pile mark across mid thorax, intermittent. Segment 2 (scutellum) almost entirely yellow.
Thorax side has oblong yellow spot, with a small spot below it. Another paler yellow spot behind wing base.
Wings: Wing knob (tegulae) black, large and raised, but difficult to see. Top half of wings dark, rest clear. The boot shape (R4+5) is more indented than the other Flower Flies Syrphidae and shows as a dark V-shape in the wing. A small vein just before the boot is also dark. Halteres yellow.
Legs: Thighs (femora) black to reddish-brown with yellowish base and tips. Hind thigh long. Shins (tibiae) reddish-brown to yellow with base and tip brownish-yellow. Hind shin thicker at tip. Feet reddish-brown, toes yellow. Male legs usually darker than female’s.
Abdomen: Long, parallel-sided. Black with yellow stripes.
Segment 1 smaller than other segments, sides constricted. Large yellow patch covering side edges.
Segment 2 has a wide, slightly raise yellow stripe, covering lower half of segment.
Segment 3 has a narrow stripe on lower margin.
Segment 4 is long, with a very narrow stripe on lower margin on female; male has stripe much wider near center.
Similar Species: Ceriana (Sphiximorpha willistoni) has no pedicle on antenna and faint, yellow U-shaped marks on abdomen.
Size: 9 to 12 mm.
Food: Dogwood Cornus, Withe Rod Viburnum nudum var. cassinoides Nannyberry Viburnum lentago. New Jersey Tea, Elderberry, Parsnip Pastinace sativa.
Flight Time: May to late July
Life Cycle: Females lay eggs in the afternoon in sap-soaked tree holes like Sweet Gum Liquidambar styraciflua and Cottonwood (Poplar). These flies are mimics of Mason Wasp Ancistrocera and Paper Wasps Polistes.
Comments: Essex County per photos. Probably extremely rare in s. w. Ontario, only recorded once in May, 2013 (blurry photos). In central and northern Ontario. The type specimen is from Guelph. Also in Quebec.
For information on synonyms, references and type specimens see next page