maize calligrapher

Maize calligrapher is an uncommon, small, typical hover fly. It occurs in North America, Central America, and South America. In the United States, it occurs east of the Great Plains and across the southwest from Texas to southern California. It also occurs in southern Canada from Nova Scotia to Ontario. Its spread into the Maritime Provinces is recent, just in the early 2000s.

The larvae feed on the pollen and sap of corn. Adults are active in Minnesota from late July to mid-September. They are found in agricultural areas. They feed on the pollen of corn and sorghum, and they have been recorded on plantain.

Adults are ¼″ to ⅜″ (7.0 to 9.0 mm) in length. The body is somewhat elongated, slender, mostly black, and shiny.

The head is small, hemispherical, narrow, black, and shiny. The back of the head is strongly concave and closely appressed to the front of the thorax. On the male, the face is yellow, with dense white hairs on the sides but bare, shiny, and yellow in the middle. On the female, the face is brown in the middle. 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 narrowly indented on the rear margin in the shape of a broad triangle. They 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. When viewed from the side, the antennae are in the middle of the head. They have three segments and are short, shorter than the head. The first two segments (scape and pedicel) are yellow. The third segment (flagellum) is orange at the base and is covered with yellow hairs. At the base of the flagellum there is a long, forward-pointing bristle (arista) on the upper side. The arista is bare, not plume-like. The protruding mouthpart (proboscis) is short and fleshy.

The large front portion of the thorax (scutum) is black and shiny, with a very diffuse, yellow, narrow or broad, longitudinal stripe on each side. On the side of the thorax there are several yellow plates (sclerites), including a large spot before the wing bases, that together form a continuous yellow band from the front to the rear. 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 small plate at the rear part of the thorax (scutellum) is yellow and is covered with black hairs.

The abdomen is parallel sided and mostly black above and on the sides. On the male, the fifth abdominal segment (tergite) is visible from above, a feature that distinguishes the subfamily Syrphinae. On both sexes, the first tergite is short and mostly black, but with yellow on the front and sides. The second tergite has a narrow, unbroken, yellow band in the middle. The third and fourth tergites are yellow. There is a narrow, black, longitudinal stripe on each side close to the middle. Each stripe widens into an inverse L-shape near the front margin, approaching but not reaching the lateral margin, and each connects with a thick black band on the rear margin. The rear band widens at the lateral margins halfway to the front margin. The fifth tergite is similar, but the longitudinal stripes are merged together, not separated. Together, they form a squat T-shape.

The legs are mostly yellow. The third segment (femur) and fourth segment (tibia) of each leg is yellow.

The wings are mostly clear except for a region (stigma) on the leading edge that is lightly tinted smoky brown. 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.

Total length: ¼″ to ⅜″ (7.0 to 9.0 mm)

Agricultural areas

Late July to mid-September

Pollen and sap of corn

Pollen of corn and sorghum

Sources

29, 30, 82, 83.

TELFORD, H. S. 1939. The Syrphidae of Minnesota. Univ. of Minn. Agric. Exp. Sta. Tech. Bull. No. 140, 76 pp.

Widespread but uncommon

The subfamily Syrphinae was traditionally divided into four tribes, Bacchini, Paragini, Syrphini and Toxomerini. The genus Toxomerus was placed in the tribe Toxomerini, and it was the only genus in that tribe. Several molecular studies between 2008 and 2016 showed that including the tribes Paragini and Toxomerini made the tribe Syrphini include only organisms from a common ancestor or ancestral group, but not all of the descendants of that ancestor or group – it was paraphyletic, and therefore invalid. A recent phylogenetic and evolutionary analysis of the subfamily Syrphinae (Mengual et al., 2022) showed that the family comprised just three major lineages of tribal rank, Melanostomini, Bacchini and Syrphini, and that Syrphini contained the former tribes Paragini and Toxomerini.

Toxomerus politus Maize calligrapher

Toxomerus politus, maize calligrapher, photographed at Barnes Prairie, Racine Co. Wisconsin, on August 11, 2021.

Exploring the World of Toxomerus politus (Maize Calligraphy)
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Toxomerus Politus
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Babette Kis
8/11/2021

Location: Barnes Prairie, Racine Co., WI

Toxomerus politus, maize calligrapher, photographed at Barnes Prairie, Racine Co. Wisconsin, on August 11, 2021.