DIGITAL FIELD GUIDE: WASPS (Order: Hymenoptera)
Eumenes sp.
<-- from Key Location 7a or 14b
Identification features: Eumenes is a common visitor to flowering plants in the Botanical Gardens. This is a mostly yellow wasp, about an inch long, and at first glance looks like the common paper wasps often called yellow jackets. However she is easily recognized by her distinctive abdominal shape, a yellow bulb or turban attached to the thorax by a thickened yellow stalk. She is not thread-waisted, but the abdomen is clearly separated from the thorax, and is therefore, petiolate. Although Eumenes’ overall color is yellow, it is heavily decorated in shades of brown. Like other Vespid wasps, she holds her wings folded longitudinally when she is not in flight. If you can get a close look at her face, you’ll see another key Vespid wasp feature: her eyes are strongly notched along the inner margin.
Nesting habit and prey: Eumenes is a solitary wasp. Her common name, potter wasp, describes her habit of building a small mud pot which she provisions for her young. She does not gather mud, but rather carries water in her mouth to dry dirt and makes her own mud. Again, using her mandibles, she makes little mud balls and transports them back to her nest site. She makes several hundred trips, and takes up to two hours, to build one pot. When the pot is finished, she inserts her bulbous abdomen into the pot and lays one egg. Then she hunts for caterpillars and bug nymphs, stinging them, paralyzing, but not killing them. She brings them back to the nest pot, stuffs them in, and seals the nest. Then she goes off to start another nest.
Polistes as pollinator: Eumenes has a short tongue and usually nectars at plants with shallow flowers such as soapberry, Texas kidneywood, seepwillow, Mexican thistle, and various composites. But she can get nectar from flowers with long floral tubes. Using her mandibles, she slices a hole in the base of a floral tube, inserts her tongue and slurps out the nectar. This is commonly referred to as “nectar robbing,” alluding to the idea that flowers reward insects for moving their pollen around by providing nectar, but some insects take the reward without doing the “work” of pollination.
