Saropogon Robber Fly

About the Saropogon Robber Fly

This striking robber fly, with a black thorax lined in silver and a bright orange abdomen, appears to belong to the genus Saropogon, a group of stout robber flies found mostly in the southwestern United States and Mexico. Many Saropogon species share this orange-bellied look, and separating them usually requires examining a specimen, so it is identified here only to genus. It has the classic robber fly features: huge dark eyes, a dense white beard of bristles over the face, a short piercing beak, smoky wings, and strong, spiny black legs.

Saropogon robber flies favor hot, open country, including sandy flats, brushy grassland, and the edges of trails and roads, where they perch low on the ground, on stones, or on bare twigs. From there they make short, fast sallies to catch passing insects, returning to the same patch of ground to feed. Prey is seized with the legs and stabbed with the beak, and the injected saliva both paralyzes the victim and begins to digest it.

The bright colors may help warn predators, and some species are thought to resemble stinging wasps. Larvae live in the soil, where they feed on other insect larvae.

This fly was photographed at Palo Alto Battlefield in Cameron County, in the lower Rio Grande Valley, on July 15, 2023.