When we think of the many beneficial insects that live in our area, Potter Wasps will not likely be high on the list. Actually, Potter Wasps are not likely to make most lists at all. However, Potter Wasps are beneficial insects that provide natural control of many types of caterpillars and even some beetle larvae.
Potter Wasps belong the family Vespidae, subfamily Eumeninae. They are related to Mud Daubers. Like Mud Daubers, these wasps are solitary, and are beneficial in that they hunt for caterpillars to paralyze and place in a brood cell, i.e., the clay-based compartment in which the wasp larva develops.
It never ceases to amaze me at the variety of adaptations used by insects to survive. In the case of the Potter wasp, each brood cell is provisioned with one to 12 caterpillars. The caterpillars are paralyzed with the wasp's sting and serve as the only source of food for the developing young. The female wasp then lays a single egg, which is attached to the top inner surface of the brood cell. There can be several generations per year.
Two species of Potter Wasps are widespread in Galveston County area. Eumenes fraternus sports a jet-black body with distinctive ivory-color markings. Pachodynerus erynnis sports a black body with broad two segments of the abdomen being reddish in color. Legs and antennae are also reddish colored.
Most area gardeners would probably not recognize Eumenes fraternus by sight but the majority of local gardeners would likely recognize their brood nests since they are quite distinctive, very common and occur in a variety of places. The brood cell constructed by a female Eumenes fraternus Potter Wasp is most interesting as it looks like a miniature pot or jug, complete with cover when it is sealed. Their brood cells are made from mud and are approximately the size of a marble.
Eumenes fraternus females will build their brood cells on vines and twigs. They very commonly will construct brood cells on window screens and other surfaces on the outside of buildings. After a wasp emerges from a brood cell as an adult, the opening is quite often perfectly round, adding to the illusion that it was thrown on a potter's wheel. The new adult wasp emerges from the brood cell by chewing a hole through the thin side of the pot. (It would seem logical for it to emerge through the neck, but this part of the structure is in fact the thickest area of the pot.)
Adult Potter Wasps are smaller than Mud Daubers, with bodies 3/8" to 3/4" long. As noted previously, the adult stage of Eumenes fraternus is black with ivory markings on the abdomen and thorax. It also has a narrow "waist." Potter Wasp adults feed on flower nectar.
While Potter Wasps are capable of stining, females do not defend their nests and they are rarely aggressive. I appreciate them for the insect control they provide in my yard, and the joy of occasionally finding a tiny "pot."
On a final note, when you do remove the nests of the Eumenes fraternus Potter Wasp, bring them to the Galveston County Extension Office in Dickinson. As a potter myself, I'd be very interested to see what would happen if these little pots were fired to 2000 degrees Fahrenheit in my kiln!
Beneficials in the Garden & Landscape is an Earth-KindTM program coordinated through Extension Horticulture at Texas A&M University. Earth-Kind uses research-proven techniques to provide maximum gardening and landscape enjoyment while preserving and protecting our environment.
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