Mud Dauber Wasp
Mud daubers are solitary wasps that construct small nests of mud in or around homes, sheds, and barns and under open structures, bridges and similar sites. Several species exist in Iowa. These wasps are long and slender with a narrow, thread-like waist. Some are a solid steel blue or black but others have additional yellow markings.
This wasp group is named for the nests that are made from mud collected by the females. Mud is rolled into a ball, carried to the nest and molded into place with the wasp's mandibles. There are three different wasps that practice this behavior. The black and yellow mud dauber builds a series of cylindrical cells that are eventually plastered over with mud to form a smooth mud nest about the size of a fist. The organ-pipe mud dauber, a more robust, black species, builds cylindrical tubes resembling pipe-organ pipes. The third species is a beautiful metallic-blue wasp with blue wings. This one does not build its own mud nest but instead uses the abandoned nests of the black and yellow mud dauber.
After completing the mud nest the female captures several insects or spiders to provision the cells. Prey are stung and paralyzed before being placed in the nest. A single egg is deposited on the prey within each cell, and the cell sealed with mud. After the wasp has finished a series of cells, she departs and does not return. The larvae that hatch from the eggs feed on the prey items left by the adult wasp. New adult wasps emerge to start the process over again.
Wasps usually evoke a great deal of anxiety or fear. However, solitary wasps such as the mud daubers do not defend their nest the way social wasps such as hornets and yellowjackets do. Mud daubers are very unlikely to sting, even when thoroughly aroused. They may sting if mishandled.
Control of these insects is not warranted since they normally pose little threat. Rather, mud daubers should be regarded as beneficial, since they remove and use as prey many species of spiders which most people find disagreeable. The mud nests can be scraped off and discarded at night if they are objectionable, or wasp and hornet aerosol sprays can be used to treat nests if desired. There is no proven method that is effective in discouraging wasps from building nests in sheltered or protected areas. Prompt and frequent removal of nests is suggested in areas favored by the wasps. Pictures of the nests can be viewed here.