DIGITAL FIELD GUIDE: WASPS (Order: Hymenoptera)
Pepsis sp.
<-- from Key Location 1a
Identification features: The tarantula hawk wasp is the most visible member of the spider-wasp family (Pompilidae). This is a large, robust wasp, with a body up to two inches long or more. These large wasps are iridescent blue-black, though we have observed some that are shiny blue or even greenish blue. They usually have bright orange wings, though the wings fade with age, and sometimes they are black to begin with. The antennae are usually black, but sometimes orange. Females tend to hold their antenna curled, while males hold theirs straight, however this is not a completely reliable way to tell the sexes apart. This is a large wasp that you will definitely notice as it maneuvers around and between shrubs, its long hind legs trailing away from its body. It often flies relatively slowly and at about eye level, and makes a loud, buzzy rattle.
Nesting habit and prey: Pepsis can deliver a powerful sting—one of the most painful stings in the insect world. Only females can sting, and fortunately, they are not aggressive; their venom is reserved for their prey.
Pepsis is a solitary wasp, and the females build and provision the nest. She excavates a burrow in the ground, then goes out to hunt. Pepsis earns her common name, Tarantula hawk, by hunting tarantulas. When she locates a spider, she stings it (this is why she needs such powerful venom). The sting does not kill the spider, but only paralyzes it. If the wasp has captured the spider at the spider’s burrow, she will stuff it back into its own nest, lay her egg upon it, and seal up the nest. If the spider is captured away from its nest, Pepsis drags it back to her own burrow. When the wasp larvae emerges, it feeds on the living but paralyzed spider, eating the non-vital parts first, while the spider stays alive (fresh), for 20 days. Finally, the larvae spins a cocoon, pupates (metamorphoses), and emerges as an adult wasp. If it is early enough in the season, the wasp will emerge, mate, and start the process over again. Later in the season, the wasp will pass the winter in its cocoon and emerge in spring.
Pepsis as pollinator: As an adult, Pepsis sips nectar for her own sustenance. As she moves from plant to plant, she pushes her head into flowers, reaching for nectar with her short tongue (glossa). This wasp has been observed on many plants, including seepwillow, kidneywood, soapberry, and sumacs. Other preferred plants are milkweeds and crotons. These plants have small, shallow, whitish flowers. Pepsis cannot reach into deep-throated flowers, however it has been observed crawling into large, wide-throated flowers such as ceniza and desert willow to get to nectar.
