Mud daubers are familiar wasps with narrow or threadlike waists. These solitary wasps belong to a number of related groups, but we call them “mud daubers” because they all build their nests out of mud. You can identify the different species by coloration and by the distinctive nest architecture.
The black-and-yellow mud dauber (Sceliphron caementarium) constructs nest cells side by side or on top of one another; the final product is rounded and about the size of a lemon or a fist.
The organ pipe mud dauber (Trypoxylon politum) is black with blue wings, with white “stockings” on the hind legs. It makes vertical, parallel rows of cells; the finished product looks like a pipe organ.
The blue mud dauber (Chalybion californicum) is a pretty metallic blue; it does not build nests but instead reuses those of one of the other species. Instead of mud, it carries water, which it uses to soften and remodel the mud of the older nests.