I requested a species creation on Pepsis thisbe. Bug guide suggest this is the mostly candidate. http://bugguide.net/node/view/3975
Tarantula hawk stings are considered to be the most painful of any North American insect. Christopher Starr wrote an article entitled, "A Pain Scale for Bee, Wasp and Ant Stings." On a scale of one to four, Pepsis formosa was one of only two insects to rate a four. This compares with a one for a Solenopsis xyloni (desert fire ant), two for a Apis mellifera (honey bee) and three for a Dasymutilla klugii (velvet ant).
One researcher described the tarantula hawk’s sting this way: "To me, the pain is like an electric wand that hits you, inducing an immediate, excruciating pain that simply shuts down one’s ability to do anything, except, perhaps, scream. Mental discipline simply does not work in these situations. The pain for me lasted only about three minutes, during which time the sting area was insensitive to touch, i.e., a pencil point poked near the sting resulted only in a dull deep pressure pain."
Read more: http://www.desertusa.com/insects/tarantula-hawks.html#ixzz4D0vNszbt