Running Crab Spider
Philodromus sp.
This spider (male) was found hunting on twigs of Velvet Mesquite (Prosopis velutina) along French Creek in the Bradshaw Mountains, Yavapai Co., Arizona. 24 May 2009. It is about 8 mm long.
Philodromidae -- Running Crab Spider Family
Running Crab Spiders, family Philodromidae, hunt insect prey without a web. Normally they sit and wait at a strategic point upon a branch or stem where their supurb camouflage makes them nearly impossible to find. The specimen at left has the same color and texture as mesquite twigs. They can run rapidly in short spurts to capture prey which they detect mostly by vibration.
The first two pair of legs are rotated to face forward and are about equal in length. There are two rows of four small eyes; the Posterior lateral eyes are situated on bumps. A number of species may be encountered within the realm of the Sonoran Desert, mostly upon woody plants or occasionally on the soil or rocky surfaces.