Toxomerus marginatus, also known as the margined calligrapher fly, is a common species of hoverfly.

[1] Smith & Chaney 2007 finds T. marginatus is the most numerous of the Syrphidae species controlling aphids in lettuce fields on California's Central Coast.

For terminology see Speight key to genera and glossary 5–6 mm (0.20–0.24 in) The face is whitish yellow and thinly pollinose.

The eye has a distinct triangular emargination on the posterior margin at or above the level of the antenna, is bare.

The scutum is olive black, but not very glossy, with a distinct ashy grey median stripe bordered narrowly by brownish coloration on either side.

The first and second segments are yellow pilose, The third and fourth segments each have a median line and a large, somewhat oblique spot on each side that reaches the base of the segment.They have lateral and submedial black vittae connected posteriorly by a black fascia, which is sometimes interrupted in the medial point of the tergum, and submedial maculate vittae.