the black-and-yellow mud-daubers often “sing” (vibrate or sonicate) while spreading mud, and sometimes when collecting it. Presumably, the vibrations help distribute the mud evenly. The mud-daubers visit the same mud and water sources repeatedly, but different shades of “mud brown” can be seen on most nests.
Black-and-yellow mud-dauber build a simple, one-cell, urn-shaped nest that is attached to crevices, cracks and corners. Each nest contains one egg. Usually, they clump several nests together and plaster more mud over them.
Blue mud-daubers frequently appropriate old nests of black-and-yellow mud-daubers. They carry water to them and recondition them for their own purposes. The two species commonly occupy the same barns, porches, or other nest sites.
Organ-pipe mud-daubers build their very distinctive and elegant tubes on vertical or horizontal faces of walls, cliffs, bridges, overhangs and shelter caves or other structures.
All three species may occupy the same sites year after year, creating large numbers of nests. Mud-dauber nests can last many years in protected locations and are often used as nest sites by other kinds of wasps and bees, as well as other types of insects.
Like most other wasps, mud-daubers are predators. The females not only build the nests, but they hunt to provision them. However, pipe-organ mud-dauber males have reportedly brought spiders to the nest, and they aid in nest-guarding.
Adults of both sexes frequently drink flower nectar, but they stock their nests with spiders, which serve as food for the mud-daubers’ offspring. Like connoisseurs, they prefer particular kinds of spiders, and particular sizes of spiders for their larders. Instead of stocking a nest cell with one or two large spiders, mud-daubers cram as many as two dozen small spiders into a nest cell. They appear to know exactly what they are hunting for, and where to find it.
Black- and -yellow mud-daubers primarily prey on relatively small, colorful spiders, such as crab spiders (and related groups), orb weavers and some jumping spiders. They usually find them in and around vegetation.
Blue mud-daubers prefer immature black widow spiders and their relatives. They hunt them in dry areas, such as outbuildings, rocky areas and stone piles.
Pipe-organ mud-daubers generally provision their nests with various kinds of orb weavers, but their diet includes other kinds of spiders, as well.
To capture a spider, the wasp grabs it and stings it into submission. The venom from the sting does not kill the spider, but paralyzes and preserves it so it can be transported and stored in the nest cell until consumed by the larva. A mud-dauber usually lays its egg on the prey item and then seals it into the nest cell with a mud cap. It then builds another cell or nest. Missouri’s mud-daubers generally have two generations per year. The young survive the winter inside the nest.
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.
The muddy nests of mud-daubers are an occasional nuisance to some homeowners, but the wasps themselves are not aggressive or dangerous. However, they will sting if handled. A trowel and a hose can be used to remove old nests.
Observing a mud-dauber nest is an interesting and rewarding experience. It’s also an effective way to learn patience and refine observation skills. The behavior of these interesting native insects can be observed very closely, but—as was my experience—the wasps may observe you in return.