Toxomerus politus

Flower Fly
Toxomerus politus

Flower Fly Toxomerus politus female Aug 17, 2016. Leamington, Ontario.
Flower Fly Toxomerus politus female Aug 17, 2016. Leamington, Ontario.

Identification:
Head: Face yellow below antenna. Above antenna solid white on male; two white stripes up inner eye margin on female, light brownish between stripes. Eyes red, hind margins curved at center, covered with white hair.
Antenna: Yellow, slight reddish tint on female.
Thorax: Metallic blackish-bronze. Segment 1 (scutum) has obvious white pile stripe down center; outside edges of segment bordered with a yellow stripe. Segment 2 (scutellum or half-moon) yellow, may be partly covered with brownish pile. Thorax sides dark brown with series of oblong and round yellow spots. Another small yellow spot above front leg.

Flower Fly Toxomerus politus male on Little Bluestem Schizachyrium scoparium, Sep 08, 2007, Wheatley, Ontario.
Flower Fly Toxomerus politus male on Little Bluestem Schizachyrium scoparium, Sep 08, 2007, Wheatley, Ontario.

Wings: Wings very slightly tinted yellowish. Darker yellowish along outside edge (costa), sometimes appears whitish. Stigma brownish-yellow. Halteres yellow.

Legs: Pale yellowish. Hind feet more reddish-yellow; last foot segment brown.

 

 

Flower Fly Toxomerus politus female, Aug 22, 2015, Leamington, Ontario.
Flower Fly Toxomerus politus female, Aug 22, 2015, Leamington, Ontario.

Abdomen: Black with yellow to orangish stripes; stripes ‘bleed’ or coalescence.
Segment 1: Wide yellow stripe across segment.
Segment 2 & 3: Narrow yellow stripe across base of segment. Wide stripe below it. Longitudinal yellow line down center. On male, lower stripe widens each side of center and is interrupted, exposing the complete longitudinal center stripe. Female sometimes has segment 3 wide stripe interrupted at center, like the male.

Flower Fly Toxomerus politus male on Goldenrod, Sep 07, 2004, Wheatley, Ontario.
Flower Fly Toxomerus politus male on Goldenrod, Sep 07, 2004, Wheatley, Ontario.

Segment 4: Stripe on base may be narrow or wide, depending on age, and sometimes becomes whitish. A black T-shaped line below the base stripe, not reaching side edges. Rest of segment yellow, V-shaped.
Segment 5: Entirely yellow.
Underside yellow.

Size: 7 to 9 mm long.

Habitat: Meadows with tall grasses, farm fields with corn.

Flower Fly Toxomerus politus male on Big Bluestem Andropogon. Aug 17, 2016, Leamington, Ontario.
Flower Fly Toxomerus politus male on Big Bluestem Andropogon. Aug 17, 2016, Leamington, Ontario.

Food: Adults and larvae feed on grass and some flower pollen, like goldenrod.

Flight Time: July to September.

Life Cycle: Females lay eggs in flowers of tall grasses like Sorghum species, Big Bluestem Andropogon and Maiden Grass Miscanthus sinensis and corn. Larvae feed on pollen from these flowers and pupate in the flower or seed heads. T. politus is the only Toxomerus that does not feed on aphids.

Comments: Essex County – Point Pelee. Extends to Toronto area.

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

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