common flower fly

Common flower fly is a common, small to medium-sized, typical hover fly. It occurs worldwide across the Northern Hemisphere, including in Europe, Asia, and North America. It occurs across the United States, but it is absent from the Great Plains and the Great Basin, and it is mostly absent from the deep south. It is abundant in the northeast, less common in Minnesota.

Adults are active from April to mid-November, but they are most abundant in May and August. They are found in a wide variety of habitats, including deciduous and coniferous forests, meadows, and fields. However, their preferred habitats are around humans and their environmental modifications (synanthropic), including farmland, horticulture land, orchards, and suburban gardens. They feed on the flower nectar and pollen of a wide variety of forbs, trees, and shrubs. The larvae are predatory, feeding on aphids and adelgids, and on the larvae of beetles, butterflies, and moths.

Adults are 5⁄16″ to ½″ (8.1 to 13.3 mm) in length. The body is robust and black with yellow markings. The markings on common flower fly are the most variable of any of the North American Syrphus species.

The head is broader than the thorax and hemispherical, not flattened. 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 bare, with no erect hairs. On the male they abruptly converge and meet at the top of the head in front of the ocelli. On the female they do not meet. The upper side of the head (vertex) is black. The upper part of the face (frons) is dark, and it is densely covered with dark hairs. The face is usually entirely yellow, but there is rarely an indistinct vertical brown stripe in the middle. The antennae are short and have three segments. They are mostly brown, but the underside of the third segment (flagellum) is short, oval, orange at the base, and broadly rounded at the tip. Near the base of the flagellum there is a long, forward-pointing bristle (arista) on the upper side.

The large plate on the front portion of the thorax (scutum) is shiny and greenish gold to black, and it is moderately covered with erect yellow hairs. There is a groove (transverse suture) across the scutum near the middle just before the wing bases. There is sometimes a narrow, dark, longitudinal stripe in the middle (middorsal) with a similar stripe on each side (subdorsal). The lateral margins are usually slightly yellowish or greenish gray. On each side of the scutum, in the shoulder (humeral) area just behind the head, there is a small plate (postpronotum). The postpronotum is bare, with no hairs or bristles. Unfortunately, this is not visible without first removing the fly’s head. The plate on the underside of the second thoracic segment (katepisternum) has an upper and lower hair patch. The patches are joined together at the rear by a narrow band of hairs. The area below a small plate on the side of the thorax (meron) and in front of the base of the third pair of legs (metacoxa) is called the metasternum. The metasternum is bare, with no hairs. The balancing organs (halteres) are yellow.

The small plate at the rear part of the thorax (scutellum) is yellow and is moderately covered with erect black hairs.

The abdomen is broad, oval, and black, with distinct yellow bands. The upper plate (tergite) on segment 1 is entirely black. Tergite 2 is black with two yellow marks near the base, effectively a yellow band broadly interrupted in the middle. Tergites 3 and 4 have a sharply defined yellow band near the base. The band is often somewhat wavy, and it extends to the lateral margin on each side. It is complete, but sometimes narrowly split in the middle by an orange stripe. Tergite 4 also has a narrow yellow band at the rear margin.

The wings are mostly clear. The entire wing surface is covered with minute hairs (microtrichia), including all of cell bm. The pigmented region (stigma) near the leading edge of the wing is a diffuse smoky brown patch more than twice as long as wide. There is a false (spurious) vein between the radius (R) and media (M) veins. The anal cell is long and is closed near the wing margin. The marginal, R₅, and M₂ cells are also closed. There are two membranous lobes (calypters) at the base of each wing that cover the haltere. There are long hairs on the upper surface of the lower calypter. This should not be confused with hairs on the edge of the calypter. This feature may require a hand lens or microscope to see.

The legs are mostly yellow. On the hind legs of the male, the basal two-thirds of the third segment (femur) may be either yellow or black. On the female, the femur on the middle legs is black just at the base, and the femur on the hind legs is usually entirely yellow, sometimes black just at the base. On both sexes, the last part of each leg (tarsus), corresponding to the foot, is brown.

Total length: 5⁄16″ to ½″ (8.1 to 13.3 mm)

Deciduous and coniferous forests, farmland, horticulture land, orchards, and suburban gardens

April to mid-November

Aphids and adelgids, and on the larvae of beetles, butterflies, and moths

Flower nectar and pollen of a wide variety of forbs, trees, and shrubs

Sources

24, 27, 29, 30, 82, 83.

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

Common and widespread

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