These solitary wasps are named for their ability to construct small nests of mud in or around homes, porches, sheds, and under open structures. They are long and slender with a narrow, thread-like waist about 3/4″ long. Some are a solid steel blue or black but others have additional yellow markings. These wasps do not defend their nests in the way social wasps do and are a much less aggressive than species than yellow jackets.
These wasps will roll mud into a ball and fashion out a nest with their mandibles. After completing the nest, the female captures and paralyzes insects or spiders as food for the soon to hatch larvae. A single egg is deposited on the prey within each cell, and the cell is sealed. After finishing several nest cells, the wasp will abandon the nest. The larvae that hatch from the eggs will feed on the prey. New adult wasps emerge to start the process over again.