Several species of the wasps known as "tarantula hawks" inhabit the desert lands of the southwest. Pepsis formosa and Pepsis thisbe are probably the two most common. Wasps in the genus Hemipepsis are also known as "tarantula hawks." The species are difficult to distinguish.
Description
Body lengths measures up to two inches, and the wasps are rather robust, which provides good protection during encounters with tarantulas. The insects are metallic blue-black with wings that are blue-black, orangish or mahogany in color. This is another group of insects which, like velvet ants, have aposematic coloring – that is, conspicuous warning coloring – which warns potential predators that this is a meal that might be more painful that it is worth.
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. P. thisbe is the most northern ranging of the genus.
Predator and Prey
Only a few animals, such as roadrunners, eat tarantula hawks. The wasps are "nectivorous," and they have been known to become "flight-challenged" after consuming fermented fruit.
Habits and Habitat
Tarantula hawks are most active in the summer, during the day, although they avoid the highest temperatures. Females give the wasps their common name. Like all members of this genus, they require a spider to serve as host for their larvae, and in the case of the local species, tarantulas are the preferred nursery.
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.