These are usually known as mud daubers or dirt daubers because of their tendency to build nests out of mud. The nests are several cylinders, or tubes, around 1' long. Each tube, or cell, contains several paralyzed spiders to feed the growing larva. Interestingly, each species of mud dauber uses only one species of spider as food. The colors range from shiny dark blue to bluish brown to black, and usually they have bright yellow markings. These solitary insects will not defend their nest and rarely sting people.