Tarantula Hawk (Pepsis sp)
Tarantula Hawk (Pepsis sp) on Slender Mountain Mint (Pycnanthemum tenuifolium). A male. I'd say he is P. menechma, but the experts say identifying a Pepsis species from a photo is "often impossible". Females do provision their nests with spiders, but not necessarily tarantulas. (Photo taken 7/5/14).
More info on BugGuide.