DIGITAL FIELD GUIDE: WASPS (Order: Hymenoptera)
Sphex lucae and S. texanus
Identification features: Sphecid wasps vs. Vespid wasps. These are the two most common groups of wasps in the Gardens. While each group has many and varied species, a basic difference between the two is the shape of the pronotal collar—the front edge of the thorax, just behind the head. In most Vespid wasps the collar has a definite V shape, whereas in Sphecid wasps the collar is a straight line.
We observed at least two species of Sphex wasps in the Gardens, Sphex texanus and Sphex lucae, but they are too similar to distinguish in the field. These wasps are large, robust wasps, about one inch long, and they have the characteristic thread-waist. The abdomen is attached to the thorax by a visible thread-like structure called a pedicel, and this structure is more slender and thread-like than the stalky abdominal attachment of Ammophila. It can be difficult to see the thread-waist if the wasp is moving fast or if its wings are covering the area between the thorax and abdomen. Both Sphex texanus and Sphex lucae have a black head and thorax. A bit of gold decorating is sometimes visible. The abdomen is reddish-orange or may be reddish-orange with a black marks, and slightly elongated (as compared to the more compact, light-bulb shape of Prionyx. The legs are black; wings are smokey black.
Nesting habit and prey : Sphex wasps are ground nesters and, as the females are the ones that build and provision the nest, they have a specialized structure on their front tarsi, a foretarsal rake, used to scrape sand out of the way as they dig their burrow. The Sphex species in the northern Chihuahuan Desert region prey on katydids.
Sphex as pollinator : Adult Sphex visits flowers sipping nectar for its own nourishment. Because it has a short tongue, Sphex visits plants with shallow flowers, including mortonia, soapberry, sumacs, Texas kidneywood, turpentine bush.
Sphex sp., Male
Sphex sp., Female