black-shouldered drone fly

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Black-shouldered drone fly is an early, common, hairy, medium-sized hoverfly. It occurs in the United States east of the Great Plains, and in southern Canada. It is common in Minnesota. It is one of the earliest hoverflies to emerge in the spring. Adults are found from April to late September mostly in forests. They feed on flower nectar. The larvae, known as rat-tailed maggots, are aquatic. They live in polluted water or in wet carcasses. They feed on small organisms.

Adults are robust, slightly bee-like in appearance, and ⅜″ to 9⁄16″ (10.1 to 14.0 mm) in length.

The head is hemispherical and slightly broader than the thorax. There are two large compound eyes on the sides of the head and three small simple eyes (ocelli) in a triangle on top of the head. The compound eyes are densely covered with short erect hairs, at least on the upper half. On the male they meet at the top of the head. On the female they do not. They are not spotted or banded. The face is densely hairy and is not projected forward. The antennae are short and are inserted near the middle of the head. They are dark brown and have just three segments. The first and second segments are short. The third segment is flat and longest on the bottom, shorter and rounded on top. At the base of the third segment there is a long, forward-pointing bristle (arista) on the upper side. The arista has a tight group of one to six short bristles on the upper side near the base. It is otherwise bare, not feather-like (plumose). The protruding mouthpart (proboscis) is short and fleshy.

The thorax is dark blackish-brown, shiny, unmarked, and densely covered with short, erect, whitish hairs. It has three segments. Each segment has four principal exoskeletal plates, one above, one below, and one on each side. The upper (dorsal) plates, from front to rear, are the prescutum, scutum, and scutellum. There is a convex swelling, called the posterior callus or postalar callus, on the upper rear corners of the scutum. At least some of the hair on the posterior callus and most of the hair on the base of the scutellum is black. This is the feature that gives the insect its common name, but it is difficult to see without a very clear photograph. The scutellum is not fringed.

The abdomen is black and is densely covered with short erect hairs. It has five segments. The first segment is narrow and entirely black. The second segment has a broad yellowish band that is broken in the middle. The third segment often has a similar but narrower orangish band. The second, third, and fourth segments each have a narrow white band on the rear margin. The fifth segment is small and entirely black. Some females show no yellow or orange spots on the abdomen.

The wings are mostly clear. Near the wing base there is a short cross-vein, the humeral vein (h), between the costa (C) and subcosta (Sc) veins. From the h to the base the wing is dark brown. Toward the wingtip, the second cell (pterostigma) on the leading edge (costal margin) is dark brown and distinct. There is a spurious vein between the radius (R) and media (M) veins. The R₄₊₅ vein is deeply bent (sinuous), appearing “bumped” downward in the middle. The anal cell is long and is closed near the wing margin. The marginal, R₁, R₅, and M₂ cells are also closed.

The legs are mostly black. The basal half of the fourth segment (tibia) of each leg is white and sharply demarcated.

Total length: ⅜″ to 9⁄16″ (10.1 to 14.0 mm)

Forests

April to late September (CCESR)

Adults overwinter.

Small organisms

Flower nectar

Sources

24, 27, 29, 30, 82.

Telford, Horace S.. (1939). The Syrphidae of Minnesota. University of Minnesota. Minnesota Agricultural Experiment Station.

Common in Minnesota

Location: Woodbury, MN

Location: Woodbury, MN

Location: Woodbury, MN