The more familiar species are up to 5 cm (2.0 in) long, with blue-black bodies and bright, rust-colored wings (other species have black wings with blue highlights), making them among the largest of wasps. The vivid coloration found on the bodies, and especially wings, of these wasps is an aposematism, advertising to potential predators the wasps' ability to deliver a powerful sting. Their long legs have hooked claws for grappling with their victims. The stinger of a female Pepsis grossa can be up to 7 mm (1⁄4 in) long, and the sting is considered the second most painful insect sting in the world; the most painful being that of the bullet ant.
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The female tarantula hawk stings and paralyzes a tarantula, then drags the specimen to a specially prepared brooding nest, where a single egg is laid on the spider’s abdomen, and the entrance is covered. Sex of the larvae is determined by fertilization; fertilized eggs produce females while unfertilized eggs produce males. When the wasp larva hatches, it creates a small hole in the spider's abdomen, then enters and feeds voraciously, avoiding vital organs for as long as possible to keep the spider alive. After several weeks, the larva pupates. Finally, the wasp becomes an adult, and emerges from the spider's abdomen to continue the life cycle. Adult Tarantula wasps are nectarivorous. The consumption of fermented fruit sometimes intoxicates them to the point that flight becomes difficult. While the wasps tend to be most active in daytime summer months, they tend to avoid high temperatures. The male tarantula hawk does not hunt; instead, it feeds off the flowers of milkweeds, western soapberry trees, or mesquite trees (females feed on these same plants, as well). Male tarantula hawks have been observed practicing a behavior called hill-topping, in which they sit atop tall plants and watch for passing females ready to reproduce. Females are not very aggressive, in that they are hesitant to sting, but the sting is extraordinarily painful.
Worldwide distribution of tarantula hawks includes areas from India to Southeast Asia, Africa, Australia, and the Americas. Tarantula hawk species have been observed from as far north as Kirkland, Washington in the United States, and south as far as Argentina in South America, with at least 250 species living in South America. Their ability to adapt allows them to live many places.  Several species of tarantula hawk are found in the deserts of the southwestern United States, with Pepsis grossa (formerly Pepsis formosa) and Pepsis thisbe being common. The two species are difficult to distinguish, but the majority of P. grossa have metallic blue bodies and reddish antennae, which separates them from P. thisbe. Both species have bright orange wings that become transparent near the tip.
Tarantula hawk wasps are relatively docile and rarely sting without provocation. However, the sting—particularly that of P. grossa—is among the most painful of any insect, though the intense pain only lasts about three minutes. One researcher described the pain as "…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." In terms of scale, the wasp's sting is rated near the top of the Schmidt sting pain index, second only to that of the bullet ant, and is described by Schmidt as "blinding, fierce [and] shockingly electric". Because of their extremely large stingers, very few animals are able to eat them; one of the few animals that can is the roadrunner. Many predatory animals avoid these wasps, and many different insects mimic them, including various other wasps and bees (Müllerian mimics), as well as moths, flies (e.g., mydas flies), and beetles (e.g., Tragidion) (Batesian mimics).
Aside from the possibility of triggering an allergic reaction, the sting is not dangerous and does not require medical attention. Local redness appears in most cases after the pain, and lasts for up to a week.
State insect of New Mexico
The U.S. state of New Mexico chose the tarantula hawk in 1989 to become its official state insect. Its selection was prompted by a group of elementary school children from Edgewood doing research on states that had adopted state insects. They selected three insects as candidates and mailed ballots to all schools for a statewide election. The winner was the tarantula hawk wasp (specifically, P. formosa).
|Tarantula hawk wasp|
- "The wasp that kills tarantulas". BBC Earth. 13 January 2015. Retrieved 15 January 2015.
- Phillips, Steven J.; Comus, Patricia Wentworth, eds. (2000). A Natural History of the Sonoran Desert. University of California Press. pp. 464–466. ISBN 0-520-21980-5.
- "Tarantula Hawks - DesertUSA". Retrieved 2010-07-26.
- Vardy, C.R. (2002). "The New World tarantula-hawk wasp genus Pepsis Fabricius (Hymenoptera: Pompilidae). Part 2. The P. grossa- to P. deaurata-groups." http://www.repository.naturalis.nl/document/46718
- Conniff, Richard (2009-08-10). "Oh, Sting, Where Is Thy Death?". The New York Times. Retrieved 2010-05-24.
- Schmidt, J. O., Blum, M. S., and Overal, W. L. "Hemolytic activities of stinging insect venoms", Archives of Insect Biochemistry and Physiology, 1:155–160, 1984.
- NM Legislature visitors guide (PDF). New Mexico Legislature. p. 33.
Media related to Pepsis at Wikimedia Commons
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