Wasps in the genus Sceliphron are known as "mud daubers" because. . . they fashion their nests out of mud. These nests can be found in protected areas with overhanging structures, such as barns, garages and the eaves of houses. Mud daubers rarely sting humans, but will if roughly handled; they reserve their sting for prey. Unlike paper wasps and other more social species, they don't defend their nests. Different species of Sceliphron build different styles of nest - for example, the black-and-yellow mud dauber (Sceliphron caementarium) constructs nest cells side by side or on top of one another, producing a rounded nest roughly the size of a lemon. They can be recognized by their long, narrow "waists".