It's noon on a hot August day here, not far from where the Similkameen River crosses into the United States. Dusty sagebrush shimmers in the heat. Grasshoppers with red or yellow wings crackle by. Birders come here in the cool early morning to see the rare Sage Thrasher and maybe a Grasshopper Sparrow. I come here for the robber flies, but I don't arrive until the sun beats down mercilessly.
Many robber flies are hard to find, but here they are abundant and diverse.
A bit smaller, but just as aggressive, a Stenopogon bumbles by carrying the impaled corpse of a clearwing moth. The prey is at least twice as heavy as the fly, but somehow this fierce predator has managed to get airborne with its catch. But where a highwayman wants only cash and valuables, a robber fly is after its victim s body. It grabs its insect prey with bristly legs then kills it with an injection of neurotoxic saliva from its sharp proboscis. The fluid also dissolves the body contents and the fly sucks the prey dry just like you'd devour a milkshake.