Robber flies

by Wizzie Brown

Robber flies, while often startling to see in the garden, are some of the good guys. These flies feed on a wide variety of other arthropods, helping to manage pest insects in the landscape. They are a generalist predator, and capture and eat whatever insects they can.
Robber flies have elongated bodies with a tapered abdomen. Eyes are large, prominent, and have a divot between them. Size can vary from 1/16” – 2” in length. These flies have long, bristly legs that help them capture prey.
Robber flies have a complete life cycle – egg, larva, pupa, and adult. Egg masses are often laid in crevices in soil, bark, wood, or on low lying vegetation. Larvae can be found in the soil or other organic material, and are predatory. Larvae feed on eggs, larvae, or soft-bodied insects. Pupation takes place in the soil. A complete life cycle can take 1-3 years depending on species and environmental conditions.
To feed, robber files often perch in high, open locations to spot prey. Robber flies capture prey while in flight. They inject a paralyzing toxin that also liquefies the prey’s body and makes it easy for the robber fly to eat.

For more information or help with identification, contact Wizzie Brown, Texas A&M AgriLife Extension Service Program Specialist at 512.854.9600. Check out my blog at www.urban-ipm.blogspot.com
This work is supported by Crops Protection and Pest Management Competitive Grants Program [grant no. 2017-70006-27188 /project accession no. 1013905] from the USDA National Institute of Food and Agriculture.