Giant Robber Fly
Promachus albifacies
Saguaro National Monument, East Unit, Pima Maricopa Co., Arizona. 28 Aug. 2016.
Asilidae -- Robber Fly Family
This is a top aerial predator in the insect world capable of taking prey much larger than itself! They tend to sit in the sunshine on an exposed rock where they can view a swath of open space. They capture other flying insects on the wing often tumbling to the ground under the combined weight.