Somula decora

Wasp-mimic Flower Fly
Somula decora

Wasp-mimic Flower Fly Somula decora female on Poison Ivy leaf. June 17, 2008 Wheatley, Ontario.
Wasp-mimic Flower Fly Somula decora female on Poison Ivy leaf. June 17, 2008 Wheatley, Ontario.

Identification:
Head: Long. Face light yellow pile, no black stripe. Antenna base projecting. Male eyes closer together than female’s, but difficult to tell apart unless a top down view of simple eyes (ocelli).
Antenna: Brownish-black, shiny, medium length. Segment 2 short. Last segment rounded, wide; as long as 1st and 2nd combined. Bristle (arista) reddish-yellow, slightly longer than last segment.

Wasp-mimic Flower Fly Somula decora male on Dogwood leaf. June 12, 2008 Wheatley, Ontario.
Wasp-mimic Flower Fly Somula decora male on Dogwood leaf. June 12, 2008 Wheatley, Ontario.

Thorax: Black with metallic green sheen, scant yellowish pile. Segment 1 (scutum) has yellow patch on each shoulder (outside edge at base). Yellow pile around edges of segment and black pile around wing base. Segment 2 (scutellum) same color as segment 1, no fringe. Thorax side has large yellow spot with yellow hair.
Wings: Outer half of wings dark, inner half clear. Halteres yellow.
Legs: Reddish-yellow. Thighs (femora) have a dark spot at base. Hind shin (tibiae) usually darker. Feet becoming brownish, toes yellow.

Wasp-mimic Flower Fly Somula decora male on Southern Arrowwood (Viburnum) June 11, 2013 Wheatley, Ontario.
Wasp-mimic Flower Fly Somula decora male on Southern Arrowwood (Viburnum) June 11, 2013 Wheatley, Ontario.

Abdomen: Black, cylindrical; edged in yellow with yellow pile. Three pairs of yellow marks, wider and separated at center. First pair of marks comma-like, others wedge-shaped. Lower border of segments have yellow pile. Male tip is entirely yellow pile and hairs; female has faint pair of spots at base, fringe on tip.
Underside black with yellow line on lower border of segments.

Size: 15 to 17 mm long.

Habitat: Forests and forest edges.

Food: Prefer nectar from flowers of shrubs like Dogwood and Viburnum; often resting on their leaves.

Flight Time: Late May to late June

Life Cycle: Rat-tail type larvae found in rotholes of living trees like Tuliptree and Oaks, preferring vertical holes which do not hold water or sap fluid all season. Feed on detritus in holes. Somewhat mimics Yellowjacket Wasps.

Comments: Essex County – Ojibway Prairies. Also Hastings and Peel Counties.

Synonyms: Macquart 1847 None

References:
American Philosophical Society, 1883, Vol. 20 by Williston, pg. 330.
United States National Museum, 1886, Vol. 31: Syrphidae by Williston, pp. 216 to 217.
Biological Society of Washington, 1916, Vol. 24: Dist. of Columbia Diptera by Banks, et al., pg. 191.
University of Kansas Science Bulletin, 1924, Vol. 15: Syrphidae from North of Mexico by Curran, pp. 161 to 162.
Proceedings of the Entomological Society of Washington, 1982, Vol. 84, #3: Larval Habits and Mate-seeking sites of Flower Flies by Maier, pg. 605.
The Great Lakes Entomologist, 1989, Vol. 22 #2: Systematics, Ecology and Host Associations of Naiadacarus (Acari: Acaridae) in the Great Lakes Region by O’Connor, pp. 81 to 91.

Types: Unknown