Dioctria hyalipennis

Robber Fly
Dioctria hyalipennis

GenBank: 468722

Identification: From England, introduced to Boston, Mass. area around 1916.
Head: Upper head and top of head shiny black. Lower face has silvery-white pile. Mustache (mystax) white. Proboscis short, black.
Antenna: Appears Y-shaped, segments about equal in length. Black with short black hair.
Thorax: Obvious neck. Thorax raised or humped; black with  two long indented lines and a faint covering of light yellow pile. Segment 2 (scutellum) small with a line of yellow pile at base. Thorax sides have a wide stripe of whitish pollen extending down to front leg.
Wings: Wings hyaline, but appear darker when folded over body. Veins brown. Halteres light yellow.
Legs: Front and middle legs mostly yellow with black streaks, tips dark; feet black with gray pile and yellow spines and toes. Hind legs black; 1st foot segment swollen.
Abdomen: Abdomen black, shining. Lower margin of segments have a thin whitish line. First 4 male segments very narrow and constricted (appear wavy); last segments gradually widen to tip. Female abdomen flat on top side, rounded and orange on underside; much wider and thicker than male, but shorter.

Similar Species: Eudioctria albius has a shiny, plain thorax and all dark legs.

Size: 10 to 14 mm.

Habitat: Meadows, forest and field edges with large shrubs and Cedar trees.

Food: Adults feed on mostly small parasitic wasps and bees like Lasioglossum and Hylaeus. Also reported feeding on small flies Diptera and pygmy grasshoppers Tetrigidae.

Flight Time: June to July in Ontario

Life Cycle: Unknown

Comments: Essex County – Ojibway Prairies, Windsor; very common in Wheatley. Kent County – Rondeau Provincial Park. Widespread in Ontario.

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