This robber fly is approximately 3/4 inch (20 mm) in length. It has white facial hairs and dark brown eyes. The top of the thorax is brown. The male has black bulbous claspers at the end of the abdomen. The 2 and 1/4 abdominal segments next to the claspers are bright white, and the middle 3 segments are brown. The female has a dark brown abdomen and a swordlike ovipositer. The wings are clear and do not extend beyond the abdomen. The legs are red and black with spiky hairs.
The frequency of occurrence is unknown, but It has been photographed in early July in Fontenelle Forest and mid-July at Neale Woods.
There are approximately 100 species in the genus Efferia in North America. Females use their swordlike ovipositor to lay eggs in dead flower heads and cracks in the ground.
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