Mud daubers are familiar wasps with narrow or threadlike waists. These solitary wasps belong to different groups, but we call them “mud daubers” because they all build their nests out of mud. You've probably seen these nests stuck to the eaves or sides of buildings. Three species are especially common in Missouri; you can identify them by coloration and by the distinctive nest architecture.
The first two are in family Sphecidae, the thread-waisted wasps:
- The yellow-legged mud dauber, also called the black and yellow mud dauber (Sceliphron caementarium), is aptly named. It constructs nest cells side by side or on top of one another; the final product is rounded like a lump, and about the size of a lemon or a fist.
- The common blue mud dauber (Chalybion californicum) is a pretty metallic blue; it often refurbishes the nests of other types of mud daubers. The nests are often irregularly shaped with an uneven, lumpy or blobby surface. This wasp doesn't carry mud; instead, it brings water to an old nest and reworks it.
The third species is in a different family, the Crabronidae (square-headed wasps, sand wasps, and relatives):
- 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. Rather smooth, vertical surfaces are the preferred substrate.
Similar species: Mud-dauber wasps are easy to identify when you see them building their mud nests. But there are several other wasps that share characteristics with them.
- Spider wasps, for instance, are also very active and flick their wings nervously; also, they commonly hover around eaves and foundations, hunting for spiders; and they are narrow-waisted, with many of them being bluish black. However, they have spinier legs, with extra-long hind legs that typically dangle in flight, and they are often seen dragging a spider to its doom, often on the ground. Some females dig burrows into the ground, others build mud cells or use abandoned cells of mud daubers, others use preexisting holes (such as beetle-bored holes in tree trunks, or old burrows of moles or mice), and some use the spider’s own nest or cranny.
- Ammophila wasps have very narrow waists, have a nervous demeanor, and dig holes in the ground.
- The great golden digger wasp and great black wasp are larger and nest in the ground. Their narrow waists are not as pronounced. They capture katydids, grasshoppers, and crickets for their young to eat.
- Mason and potter wasps are in a different family, and they lack a prolonged narrow waist, but some of them do build nests from mud. However, these nests typically resemble little round pots or jugs affixed to a wall or other structure. Others in this group build nests in existing cavities (such as a crack in a cliff face), using mud to make walls between the brood cells.
- Grass-carrying wasps and several other narrow-waisted wasps live in Missouri, as well.
Length: about ½ to 1 inch.
Statewide.
Habitat and Conservation
In nature, nests are built in cave entrances, under rock overhangs, in hollow trees, and in similar places.
People often notice nests in barns, garages, and the eaves of houses. (Howard Ensign Evans wrote, "the passing of the outdoor privy was a sad day" for mud daubers!) These wasps often build their nests under bridges, too.
In most species, the female carries mud balls from the edge of a puddle to the nest site; a cell takes about an hour to construct. Their buzzy "singing" while applying mud to a nest is one of many interesting habits and behaviors you can enjoy.
Food
Adult mud daubers are often seen drinking nectar from flowers. This sustains them for their activities: mating, building nests, hunting, and laying eggs.
As with other insects, most growth occurs in the hungry immature stages. Adult mud daubers pack paralyzed spiders into the nest cells as provisions for their young. Stinging the spider subdues the spider and also helps preserve it, so when the grublike wasp larvae hatch, they have fresh food to eat and fuel their growth.
- Yellow-legged mud daubers prefer crab spiders and other small, colorful species.
- Common blue mud daubers use large numbers of black widow spiders.
- Organ pipe mud daubers typically provide orbweavers for their young.
Status
These wasps are solitary and do not aggressively sting people. The females are capable of stinging people but only do so if mishandled.
Mud daubers are usually considered beneficial around homes, especially since some species hunt black widow spiders, which most people deem less desirable around people.
Life Cycle
All Missouri mud daubers pass the winter as immature individuals in the nests.
The yellow-legged mud dauber has two generations each summer. The lump-shaped mud nests may include as many as 25 cells, each containing about 10 spiders (though there may be up to 40 spiders in a single cell). Before sealing each cell with mud, the female lays a single egg on one of the last spiders she stuffed into it. After completing her cluster of cells, the female often adds mud to cover and smooth over the mass.
The common blue mud dauber can have several generations in a year. As noted, it frequently refurbishes the nests of other types of mud daubers, ending up with an irregular shape with lumpy blobs on the outside. Sometimes this species rehabs a mud nest before the original occupant is done with it; in this case, the common blue mud dauber jettisons the original larvae and their spiders and replaces them with spiders she has captured and her own eggs.
Organ pipe mud daubers have one or two generations a year. Males of this species are among the few male hymenopterans (ants, bees, wasps) to stay at the nest: A male "stands guard" while a female is away collecting spiders, in order to protect against other insects that might sneak in and parasitize the nest. Mating occurs frequently on her visits to the nest. Each "pipe" contains a number of cells, each containing a few, or even up to 18 spiders and a single egg.
Human Connections
Mud dauber nests are usually considered unsightly nuisances on human buildings. However, before you eradicate your mud dauber nests, remember that these relatively harmless insects comb the environment for spiders, including black widows.
Most people would call these insects beneficial, because they would agree that any natural remedy that reduces black widows around the home is a good thing. Because common blue mud daubers (which specialize in hunting black widows) refurbish the old nests of the other two species, consider allowing any mud daubers to build nests where you can tolerate them. Mud daubers reserve their sting only for prey and rarely sting humans (they do so only if handled roughly).
Although other types of wasps may also build their nests on your house, note that some are solitary and some are social. The solitary species, such as mud daubers, do not defend their nests the way paper wasps, yellow jackets, and other colony-forming species do.
Male organ pipe mud daubers often guard the nest while the female is off gathering mud or hunting spiders. If a person approaches the nest, the male may make a loud buzzing sound in defense, but as with all wasps, the males lack stingers.
Ecosystem Connections
Mud daubers prey on spiders, controlling their numbers. Numerous other insects parasitize their nests, eating their eggs and larvae as well as the spiders intended as their food. Many birds, mammals, amphibians, and reptiles all prey on wasps, as well.
Why the crazy long waists? The narrow, elongated front portion of the abdomen provides flexibility and maneuverability for the "business" end of the abdomen. These wasps must hunt and subdue spiders (with their own long legs and venomous fangs), and during the struggle, it helps to be able to move the hind end of the abdomen, with its stinger, into position.
Several other animals build nests from mud. Cliff swallows and other swallows make juglike nests under bridges and overpasses and on cliff faces. Eastern phoebes make cup nests of mud and moss under sheltered overhangs. Several types of crayfish, such as the grassland and devil crayfishes, dig burrows into the ground topped with a chimney of dried mud. Several types of megachilid bees (especially mortar and mason bees), and digger bees (Anthophora spp.), create nest cells from mud, clay, or other materials. Humans can make homes from mud, too: think of adobe bricks, and frontier sod houses.
