[classicman]

from here

Body lengths measures up to two inches
Range
Pepsis is a New World genus, with species occurring from Argentina northward to Logan, Utah. Over 250 species are found in South America. Fifteen occur in the United States, with at least nine occurring in the deserts. Tarantula hawks occur wherever tarantulas are found.

A female wasp finds a tarantula by smell. Generally, she scampers across the ground to locate a burrow. She will enter the burrow and expel the spider, then attack it. She may also encounter a male tarantula during his search for a mate. In an attack, the wasp uses her antennae to probe the spider, which may raise its front legs and bare its fangs. (A tarantula does not always counterattack.) She then attempts to sting the spider. She might seize the spider by a leg, flip it over on its back and sting it, or she may approach from the side to deliver a sting. Once stung, the tarantula becomes paralyzed within seconds. The condition will last for the remainder of its life. The wasp may drink the body fluids oozing from the spider’s wounds or from its mouth to replenish nutrients and water she used during the attack.

If the wasp expelled her victim, she will drag it back into its own burrow, now a burial vault, lay a single egg on the spider’s abdomen, then seal the chamber. If the wasp succeeds in stinging a male tarantula on a mating hunt, she will excavate a burrow, drag the paralyzed spider inside, lay her single egg, and seal the chamber.
Once the egg hatches, the tiny grub, initially connected to the spider by the tip of its tail, bends over, attaches its head and begins to suck. It continues sucking until its final moult. It then rips open the spider's abdomen, thrusts its head and part of the thorax inside, and "feeds ravenously," as one entomologist described it. As one might hope, even for a spider, the tarantula at this point is finally dead.

Male tarantula wasps also lead an intriguing life. They engage in a behavior called "hill-topping," where they perch on taller vegetation or high points. They are strongly territorial at these sites because of the good view of the surroundings and in particular, of newly emerged virgin females, which may be receptive to mating. Once again we see that males of another species act quite like males of our own species; think of males posted up at a bar keeping an eye on the door.