Tarantula Hawks, Genus Pepsis

Imagine a wasp so fierce and strong that it can capture and drag a live tarantula across the desert sand! If you're lucky enough to witness this feat by a tarantula hawk (genus Pepsis), you'll surely never forget it. Just look with your eyes and not with your hands, because the tarantula hawk doesn't like being handled and will let you know with a painful sting. Entomologist Justin Schmidt, who devised the Schmidt Sting Pain Index, described the tarantula hawk's sting as 3 minutes of "blinding, fierce, shockingly electric pain" that feels as if "a running hair drier has been dropped into your bubble bath." 

Description

Tarantula hawks or tarantula wasp (Pepsis spp,) are so named because the females provision their offspring with live tarantulas. They are big, brilliant wasps encountered mostly in the Southwest. Tarantula hawks are easily recognized by their iridescent blue-black bodies and (usually) shiny orange wings. Some also have orange antennae, and in certain populations, the wings may be black instead of orange.

Another genus of tarantula hawks, Hemipepsis, looks similar and can easily be mistaken for Pepsis wasps, but Hemipepsis wasps tend to be smaller. Pepsis tarantula wasps range in body length from 14-50 mm (about 0.5-2.0 inches), with males considerably smaller than females. You can differentiate females from males by looking for their curled antennae. While members of the genus are fairly distinctive and easy to identify, it's difficult to identify tarantula hawks to species from a photo or during observation in the field.

Classification

Kingdom - Animalia

Phylum - Arthropoda

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Class - Insecta

Order - Hymenoptera

Family - Pompilidae

Genus - Pepsis

Diet

Adult tarantula hawks, both male, and female drink nectar from flowers and are said to be particularly fond of milkweed flowers. A tarantula hawk larva feeds on the organs and tissues of the provisioned tarantula. The newly emerged larva will feed on non-vital organs first, and save the tarantula's heart for its final instar meal.

Life Cycle

For every tarantula hawk that lives, a tarantula dies. Once she has mated, the female tarantula hawk begins the laborsome process of finding and capturing a tarantula for each egg she will lay. She immobilizes the tarantula by stinging it in a vital nerve center, and then drags it into its burrow, or into a crevice or similarly sheltered location. She then lays an egg on the paralyzed tarantula.

The tarantula hawk egg hatches in 3-4 days, and the newly emerged larva feeds on the tarantula. It molts through several instars before pupating. Pupation usually lasts 2-3 weeks, after which the new adult tarantula hawk emerges.

Special Behaviors and Defenses

When she's on the hunt for a tarantula, the female tarantula hawk will sometimes fly over the desert floor, searching for a victim. But more often, she'll look for occupied tarantula burrows. While in its burrow, a tarantula will usually cover the entrance with a silk drape, but this doesn't deter the tarantula hawk. She'll snip the silk and enter the burrow, and quickly drive the tarantula from its hiding place.

Once she has the tarantula out in the open, the determined wasp will provoke the spider by prodding it with her antennae. If the tarantula rears up on its legs, it's all but doomed. The tarantula hawk stings with precision, injecting her venom into nerves and immobilizing the spider instantly.

Range and Distribution

Tarantula hawks are New World wasps, with a range extending from the U.S. to much of South America. Only 18 Pepsis species are known to inhabit the U.S., but well over 250 species of tarantula hawks inhabit the tropical region of South America. In the U.S., all but one species are restricted to the Southwest. Pepsis elegans is the lone tarantula hawk that also lives in the eastern U.S.

Sources

• Genus Pepsis – Tarantula Hawks, Bugguide.net. Accessed online November 3, 2014.
• Revision of the Nearctic species of the pompilid genus Pepsis (Hymenoptera, Pompilidae), by Paul David Hurd. Bulletin of the AMNH; v. 98, article 4, 1952.
• Tarantula Hawks, Colorado State University. Accessed online November 3, 2014.
• Tarantula Hawk, by David B. Williams. Desert USA website. Accessed online November 3, 2014.
• National Wildlife Federation Field Guide to Insects and Spiders of North America, by Arthur V. Evans.