DIGITAL FIELD GUIDE: WASPS (Order: Hymenoptera)
Robust Yellow Group
<-- from Key Location 21a
There are two strikingly large—to two inches long—primarily yellow wasps that occur in the Gardens: Sphecius grandis and Cerceris frontata.
Identification features: Cerceris frontata is commonly known as a square-headed wasp, and when you see her, you notice how her head is wider than her thorax and very angular. Her abdomen is brown with wide, bold bands of yellow. The thorax is brown with yellow accents, and her large head is brown with yellow. Her nose (clypeus) is yellow and crescent-shaped.
Nesting habit and prey: Cerceris is a solitary wasp, and the female builds and provisions the nest, digging a hole in the ground. She preys on adult weevils (Cucurlionidae), which she paralyzes by stinging, then brings back to the nest. She stuffs the weevils into the brood cell, lays one egg on a prey item, then seals the nest.
Cerceris frontata as pollinator: Cerceris sips nectar for her own nourishment. She visits shallow flowers to get at the nectar with her short tongue. Cerceris frontata is an uncommon visitor to the Gardens, observed only a few times on Texas kidneywood and soapberry.
Identification features: Sphecius grandis is a grandly sized wasp, nearly two inches long, robust and primarily yellow, with some amber. The abdomen is encircled with wide yellow rings. The apex of the female’s abdomen tapers to a point, ending in a wicked looking stinger. However, Sphecius is not aggressive, she reserves her venom for her prey, cicadas.
Nesting habit and prey: Sphecius is a solitary ground-nesting wasp, and provisions the nest for her progeny with cicadas. She hunts the cicada, paralyzes it, then drags it back to the nest. She pushes the cicada into the brood cell, and depending on the size of the cicada, may continue provisioning until she has stuffed four or more into the brood cell. Then she lays one egg on one cicada and seals the brood cell.
Males emerge from the nest first and stake out territory near nest sites. While they are waiting for females to emerge, they also aggressively patrol and guard their territory. They find a perch, then fly out to engage intruders, grappling with rogue males and driving them away. When the females emerge, they mate once and then get on with building and provisioning the nest. The males die after just a few days.
Sphecius grandis as pollinator: Sphecius is an uncommon visitor to the Gardens, and has been observed just one time, nectaring on soapberry.