As perfectly stated in the Kaufman Field Guide to North America, robber flies “are to other insects what falcons are to other birds: swift predators on the wing.” They perch in open habitat waiting for flying prey. Once in their sights, the chase is on. A swift injection of toxins from a piercing-sucking beak immobilizes, and digestive enzymes allow the fly to suck the contents. Larvae are also predators, with individuals in this genus hunting insects in rotting wood. Look for these characteristics to know if you’re dealing with a robber fly: a long and slender body with a tapering abdomen, a “beard,” large eyes with a trough between the tops, and long legs with thick spines. We believe this individual is Laphria sadales, a species that ranges across northern North America (QC-BC to PA-SD-CO-CA).
Photo by: Glenn Marangelo on 7/18/21 near Philipsburg, MT