Mud dauber Wasp Making Nest

The nest of a black and yellow mud dauber species Sceliphron caementarium is a simple, one, two or sometimes three celled, cigar-shaped mass that is attached to crevices, cracks and corners. Each cell contains one egg. Usually several cells are clumped together and covered in mud. The blue mud dauber species Chalybion californicum, another sphecid, builds mud nests, but occasionally refurbishes the abandoned nests of other species; it preys primarily on spiders.
All mud daubers may occupy the same sites year after year, creating large numbers of nests in protected locations; such sites are often used as nest sites by other kinds of wasps and bees, as well as other types of insects.
One disadvantage to making nests is that most, if not all, of the nest-maker’s offspring are concentrated in one place, making them highly vulnerable to predation. Once a predator finds a nest, it can plunder it cell by cell. A variety of parasitic wasps, ranging from extremely tiny chalcidoid wasps to larger, bright green chrysidid wasps, attack mud dauber nests. They pirate provisions and offspring as food for their own offspring.