Ceriana willistoni

Wasp-mimic Flower Fly
Ceriana (Sphiximorpha) willistoni

Wasp-mimic Flower Fly Ceriana willistoni male on Hoptree flowers Jun 11-08, Wheatley, Ontario
Wasp-mimic Flower Fly Ceriana willistoni male on Hoptree flowers Jun 11-08, Wheatley, Ontario

Identification:
Head: Face long, flat (no projections). Face black with varying yellow marks. Usually a solid yellow mark up sides of face, and touching inner eye margin before antenna base. Some have either a few yellow spots or a transverse stripe below antenna base. Above the base either a yellow V-shaped stripe (usually on male), or another series of 4 spots (usually on female). Simple eyes (ocelli) reddish-brown, raised above top of head with two, nearly touching spots of yellow behind the ocelli. Another faint brownish-yellow spot at bottom of eye (difficult to see). Male eyes touching at top before simple eyes (ocelli). Female eyes wide apart.

Wasp-mimic Flower Fly Ceriana willistoni male Jun 14-05 Wheatley, Ontario
Wasp-mimic Flower Fly Ceriana willistoni male Jun 14-05 Wheatley, Ontario

Antenna: Very long, black. Base brownish-yellow. No post (pedicle). 1st joint very long and thin. 2nd joint short; half as long as first. Last joint wider, tips sharply pointed.

Thorax: Black. Segment 1 (scutum) has yellow spot on shoulders (outside corner at base). Another yellow spot before wing bases (behind shoulder spot). A thin yellow stripe on each side of last half of segment 1. Thin line of brownish-yellow pile, intermitted across segment just before yellow stripe. Two very faint yellowish-white pile lines down middle, each side of centre (only visible in certain lights). Note: small spots behind simple eyes (ocelli) may seem like two yellow spots on base of thorax, depending on angle of head. Segment 2 (scutellum) yellow, thin margin of black surrounding the yellow. Thorax sides have oblong spot directed downward, and another smaller, oblong spot directed sideways below it. A wide, curved light yellow mark below segment 2 (scutellum).

Wasp-mimic Flower Fly Ceriana willistoni male Jun 14-05 on Blanketflower, Wheatley, Ontario
Wasp-mimic Flower Fly Ceriana willistoni male Jun 14-05 on Blanketflower, Wheatley, Ontario

Wings: Wings clear, brown all along outside edge, covering about 1/3 of wing width. Veins dark brown. Halteres yellowish.

Legs: Thighs (femora) black, faint yellow at joints. Hind thigh long, slightly thickened. Shins (tibiae) base yellowish-brown, rest black. Feet base yellow, rest black, except hind foot entirely black.

Abdomen: Black; yellow stripes are slightly raised.
Segment 1 very short and wide. No marks.
Segment 2 long and narrow, yellow mark at base on each side and yellow stripe on lower margin.
Segment 3 short, yellow stripe on lower margin. Also has very faint U-shaped, or curved yellowish line each side of centre, nearer lower margin.
Segment 4 longer, yellow stripe on lower margin. Also has more obvious, larger U-shaped yellowish line each side of centre, extending almost entire length of segment.
Tip black, no hair.

Similar Species: Ceriana abbreviata has a long post (pedicel) before the antenna, and lacks U-shaped yellow marks on abdomen.

Size: 11 to 14 mm.

Habitat: Forests and forest edges.

Food: Nectar from flowers like Blanketflower; prefers trees and shrubs like Hoptree.

Flight Time: Late-May to June

Life Cycle: Larvae found in sap soaked rotholes in living trees like Oak. Apparently they pupate on bark of same tree. Pupa 18 mm, dull black, with two large, close together white marks and row of spines down length and on each side. Sides mottled cream colour. Tip shiny black. Underside white.

Comments: Rare. Essex County – Point Pelee in cactus field May, 2012. Wheatley 2005 and 2008.

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

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