The organ pipe mud dauber is a type of wasp in the family Crabronidae. They are fairly large wasps, shiny black with pale hind tarsi. Male organ pipe mud daubers are among the few male wasps of any species to stay at the nest. A male "stands guard" while a female is away collecting spiders. Mating typically occurs on her visits to the nest. They typically build their nests in sheltered locations, and large aggregations may form with dozens to hundreds of nests in a small area.