International Mud Day


Happy International Mud Day, the day where the world celebrates all things muddy! In celebration of such a strange holiday, we’ll be talking about a beneficial wasp which can be a nuisance pest to homeowners – the mud dauber, which is also called the dirt dauber.

Mud daubers are slender wasps with long, thread-like waists. In our area, you may see the blue mud wasp or the black and yellow mud dauber. Their common names are not very imaginative, but they do provide insight on their general appearance. The blue mud wasp is metallic blue-black, while the black and yellow mud dauber is, as you might expect, black and yellow. These twitchy wasps may frighten people because of their quick, jerky, and constant movement, but the fear is unwarranted. They are not very defensive of their nests and are rarely aggressive towards people or pets. They do not form colonies like paper wasps or honey bees. They are solitary and work alone. Unrelated wasps may work and build in the same area, but they are not helping each other.

Mated female mud daubers search for sheltered areas to create their mud nests, and man-made structures seem to be a favorite location for them. The underside of overpasses can be densely packed with their nests. Some homes are more attractive to mud daubers than others, but just about every homeowner has seen at least one or two mud nests dried rock solid on the side of their home. The females look for wet mud and transport their crafting material in the form of perfectly-formed balls. The mud nests may be long, parallel, and tubular, or they may be globular, or irregular.

Adult mud daubers feed on nectar and fluids from the prey they catch, but their young feed solely on spiders. Blue mud wasps specialize on black widows, while black and yellow mud daubers are less picky about which spiders they capture. Each mud nest is packed full of spiders as food for the developing young. Each spider is stung to paralyze it and put it in a comatose state. This keeps the spiders alive but defenseless, as dead spiders would rot and spoil before the larvae could eat them.

In the case of the black and yellow mud dauber, each nest may contain up to 25 cells with each cell containing a single mud dauber egg. A dozen or so spiders may be needed to provide enough food for each of her larvae to reach adulthood. Assuming 12 spiders are needed for each of her eggs, and for a big nest with 25 cells, a single female would need to find, sting, carry, and provision a nest with 300 spiders – what a dedicated mother

Mud daubers are the most well-known mud-collecting wasps, but let us not neglect potter wasps and mason wasps. Potter wasp nests look like miniature pots, while those of mason wasps are elongate, irregular, or blob-like. Potter wasps and mason wasps collect spiders, beetle grubs, and caterpillars for their young.

Mud daubers, mason wasps, and potter wasps are not aggressive, but that doesn’t mean that they won’t sting you. They are reluctant to sting and generally won’t bother you unless you are harassing them. Use caution around any wasp and respect the space around them and their nest. If you like the idea of having fewer spiders and bugs around your home, allow these mud-builders to build their nests. You can always knock the nests down after the mud daubers have grown and left - empty nests will have an emergence hole where the wasp chewed its way out.