William F. Lyon
|Common Name||Scientific Name|
|Organpipe Mud Dauber||
Trypoxylon politum Say|
Trypoxylon clavatum Say
|Black and Yellow Mud Dauber||Sceliphron caementarium (Drury)|
|Blue Mud Dauber||Chalybion californicum (Saussure)|
Mud daubers may become a nuisance when they construct nests of mud, especially on porches, decks, sheds, eaves, attics, ceilings, walls and under roof overhangs around homes and other structures where people live, work and play. They are considered nuisance pests since nests are not defended and stings are rare. In spite of their formidable appearance, these solitary wasps are not aggressive and controls are rarely needed.
|Mud Dauber and Nests|
Adults of the organpipe mud dauber are about 1/2 to 3/4 inch long, shiny, black, elongate and slender. The inner margins of the eyes are deeply emarginate (notched), with hind leg segments (tibiae) white. Black and yellow mud daubers are about 1 to 1-1/4 inches long; black or brown with yellow markings (partially yellow legs) and thread-waisted. Blue mud daubers are about 1/2 to 3/4 inch long, metallic blue to blackish (with blue wings) and thread-waisted.
The organpipe mud dauber builds finger-like nests of mud attached to flat surfaces under roof overhangs, under eaves, etc. The nest is a series of parallel mud tubes of varying length, like a pipe organ with several or many tubes in a row. The black and yellow mud dauber is often seen around wet areas digging up balls of mud for its nest. The nest is placed on the undersides of boards, logs, rocks, etc. Nests may be a single cell or several cells placed side by side. The blue mud dauber does not make its own nest, but takes over the nest of the black and yellow mud dauber.
Mud daubers are often seen at the edge of mud puddles collecting mud to construct their tublar nests. Organpipe mud dauber nests are partitioned off with mud and each cell is provisioned with several paralyzed spiders and implanted with an egg. After eggs hatch, larvae feed on captured spiders with larvae maturing in about three weeks. Larvae spin a cocoon and overwinter. Males may guard the nest while the female forages. Mud cells may be constructed in deserted nests of the black and yellow mud dauber.
Female black and yellow mud daubers paralyze spiders, pack them into the cell with their head until full, lay one egg and seal the cell. Larvae are pale yellowish about 3/4 inch long when fully grown. Pupation occurs within a cocoon inside the cell. There are two broods with hibernation in the cocoon. Female blue mud daubers take over a mud nest, open a cell by moistening the clay with water and emptying it of spiders and the other wasp egg. They then deposit their own paralyzed spiders, lay their own egg and seal over the cell. Hosts are mostly black widow spiders.
Solitary wasps (mud daubers) are very different than the social wasps (hornets, yellowjackets and paper wasps). There is no worker caste and the queens must care for their own young. Mud dauber wasp queens use their sting to paralyze their prey (spiders) rather than to defend their nests. These wasps are non-aggressive and rarely sting unless touched or caught in clothing.
When painting buildings it is often necessary to remove the finger-like mud tubes from places which need to be painted. Nests can be removed with a putty knife and adults killed with a fly swatter, if necessary. Usually it is not necessary to control mud daubers unless their presence is a nuisance. They are beneficial to humans by sometimes killing dangerous spiders such as the black widow.
Chemical control should be considered as a last resort since these wasps are not aggressive and rarely sting unless handled. Adults can be killed with an aerosol spray containing synergized pyrethrins or resmethrin. After use of insecticides, scrape away the nest with a putty knife or other tool, and dispose of it to prevent emergence of developing young and possible infestations of dermestid beetles in the old nest. When using insecticides, follow label directions and safety precautions.
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Keith L. Smith, Associate Vice President for Ag. Adm. and Director, OSU Extension.
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