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Mud Daubers
About Mud Daubers (Mud Wasps)
Mud dauber (sometimes called “dirt dauber,” “dirt digger,” “dirt dobber,” “dirt diver”, or “mud wasp”) is a name commonly applied to a number of wasps from either the family Sphecidae or Crabronidae that build their nests from mud. Mud daubers are long, slender wasps; the latter two species above have thread-like waists. The name of this wasp group comes from the nests that are made by the females, which consist of mud molded into place by the wasp’s mandibles.
The organ-pipe mud dauber, as the name implies, builds nests in the shape of a cylindrical tube resembling an organ pipe or pan flute. The black and yellow mud dauber’s nest is composed of a series of cylindrical cells that are plastered over to form a smooth nest about the size of a lemon. The metallic-blue mud dauber forgoes building a nest altogether and simply uses the abandoned nests of the other two species and preys primarily on black widow spiders.[1]
Mud daubers are rarely aggressive. They do, however, pose a special risk to aircraft operations, as they are prone to nest in the small openings and tubes that compose aircraft pitot-static systems. Their presence in these systems can disable or impair the function of the airspeed indicator, the altimeter, and/or the vertical speed indicator. It is thought that mud dauber wasps were ultimately responsible for the crash of Birgenair Flight 301, which killed 189 passengers and crew.[2] They are also the main predator of the black and brown widow spiders.
Identifying Mud Dauber Nests
Black-and-yellow mud daubers 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 also hunt to provision them. However, pipe-organ mud dauber males have reportedly brought spiders to the nest, and they aid in nest guarding.
The Mud Dauber Diet
Adults of both sexes frequently drink flower nectar, but they stock their nests with spiders, which serve as food for their 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 diets include other kinds of spiders, as well.
Mud Daubers As Hunters
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.
