MUDDAUBERS

Mud dauber nests look like mud tubes and are often attached to walls or eaves.
Muddaubers belong to the family Sphecidae. They have a very thin waist and long, dangly legs. These wasps are incredibly beautiful, with smoky wings and a bright metallic blue body. There are more than 1,100 species in this family in North America. All are solitary with each female building an individual nest in which to lay her eggs. The nests are made out of mud, two to three inches across, with rows of round cells containing the developing embryos. The female wasp stocks each cell with a spider—food for the young wasps when they hatch.
Mud daubers are not very aggressive and rarely sting. You can leave mud daubers and their nests alone, or, if you prefer, simply remove the nest.