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.