Many wasps are capable of inflicting injury with their stings, but you have little to fear from mud daubers. They aren't social wasps, so you seldom have to deal with more than one at a time. Also, they are nonaggressive, and even in the rare circumstance when one does sting you, the result is usually little more than local pain. Consequently, removing a mud dauber nest is not challenging.
Three Common Species
In the summer months in the United States, you may come across one of three species of mud daubers: The black and yellow mud dauber (Sceliphron caementarium), the organ pipe mud dauber (Trypoxylon politum) or the blue mud dauber (Chalybion californicum). The latter two wasps are colored primarily black or blue, while the former has yellow bands; all have thread-like waists. Mud daubers are so-named because they live in nests made from mud. The black and yellow dauber makes a lemon-shaped nest, and the organ pipe dauber constructs rows of cylindrical cells that resemble organ pipes. The resourceful blue dauber reuses nests made by the other two species.
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You're most likely to see a mud dauber nest tucked away in a corner of a garage or shed or nestled underneath a roof overhang. If you're in the habit of leaving a bedroom window open, you may find a nest in the corner of the room, and it's also common to find one in the attic. Whether the nest is spherical or cylindrical, it's home to only one wasp. If you're brave enough to look inside the nest, you'll probably find one or several spiders, which are food for the progeny of the wasp that's using the nest.
How to Identify a Mud Dauber Nest
Mud dauber nests are made of mud that is brown, tan or gray. The size and shape of the nests varies. Some are cylindrical, while others are oval or round. There are even mud dauber nests that resemble the pipes of an organ. You may not notice a mud dauber nest at first. Since they are made of mud, they tend to blend in. They are usually firmly attached to a surface.
Mud daubers look much more dangerous than they are, and because they prey on harmful spiders, including young black widows, they're good to have around. For these reasons, the best reaction to finding a nest may be simply to leave it there. If it's in an inconvenient place, and leaving it isn't an option, there's no need to exterminate the insect when you remove the nest. A mud dauber will sting you only in exceptional circumstances, such as if you try to pick it up or squash it. It won't attack you if you remove its nest -- it will simply make or find another one.
Removing a Nest
Because mud daubers use mud almost exclusively to make their nests, the nests aren't difficult to remove. You can often scrape one off with a paint scraper; it may leave a ring of residue, which comes off easily with soap and water. If the nest is on an exterior wood or concrete surface, you can simply spray it with a garden hose. The mud will liquefy and fall off, and you can then clean it up with a sponge. It's difficult to stop the insect from making another nest, so the best control strategy is to keep checking for new nests and remove any you find.