These wasps capture live tarantulas to feed to their larva; the adults graze on flowers.

[5] Per Edward Essig, Milde's tarantula-hawk wasp usually measures 20–30 millimeters in length and is a metallic blue-black overall, with "the antennae reddish, dusky at extreme base in the male and the basal third dusky in the female; the wings fiery red with the bases and apices dusky".

[6] The lifespan of males is one to two months, while female Milde's tarantula-hawk wasps live for a longer span of time.

[7] In the U.S. this wasp is relatively common and widely distributed; it has been documented in California, Nevada, Arizona, New Mexico, Utah, Colorado, Texas, Oklahoma, Kansas, and Arkansas.

[9] According to Paul David Hurd Jr. the Pepsis species angustimarginata and mildei "bear such a close morphological relationship that one is led to believe they arose from the identical ancestral stock.