This Wasp Kills Black Widows: Meet the Mud Dauber

By Rhiannon Lewis-Stephenson and Tom Wheeler

The mud dauber wasp wins the award for the most badass wasp. Mud daubers, a common name for solitary wasps that build their nests out of mud, are native to California. They are avid pollinators and live on a diet of nectar, however, their larvae are fed a diet of stunned spiders that are captured and subsequently immobilized by stinging. Despite this ferocious hunting ability, mud daubers are very docile and unlikely to sting humans. 

Blue mud dauber. Photo credit Jimmy Smith, Flikr Creative Commons

Overall there are five species of mud dauber wasps in the United States, with two species of mud dauber wasps prevalent in California: the black and yellow mud dauber (Sceliphron caementarium) and the blue mud dauber (Chalybion californicum). Their names describe their look, with black and yellow mud daubers commonly mistaken for yellowjackets and paper wasps, and blue mud daubers sporting an electric blue look. While both focus on spiders as their dominant prey for their young, blue mud daubers often focus specifically on black widow spiders, making them a top predator of black widow spiders. Both mud daubers build their nests—mud mansions with small cave-like cells for their young. Daubers will look to build in areas that are sheltered and near a good supply of mud and spiders, such as under bridges or under the eaves of a house.

Mud dauber wasp. Photo Credit Ian Jacobs, Flikr Creative Commons

On that note, don’t confuse the mud dauber for other more prevalent and potentially stinging wasps. Yellowjackets, long the bane of backyard barbeques, are a voracious social wasp that will buzz about your food, trying to sneak off with a piece of meat or fruit. Most yellowjackets live in underground burrows, although the invasive German yellowjackets take up residence in home walls. And don’t confuse them for paper wasps, either. Those ubiquitous garden dwellers can be nonnative and invasive (although they do provide helpful pest control and pollination services) and generally won’t sting humans unless their intricate paper nests are disturbed. 

Spiders should be scared of mud daubers. Female daubers will sting the spider with a concoction that renders it paralyzed but alive. The spiders will then be brought back to the mud cell where momma dauber often lays an egg on the first deposited spider. Momma dauber will put into the cell all the food her young larvae will need in this life stage—up to 25 paralyzed but very alive spiders—and then seal the end of the cell. The larvae will spend its youth slowly munching on spiders, one by one, until they are all consumed, after which the young dauber pupates, breaks out the seal, and emerges as an adult. 

Adults live a brief but productive life, between three to six weeks. Active during the day, daubers are likely found mowing down on pollen, paralyzing spiders, or adding to their nest. Daubers like warm weather and are most active during late spring and summer in our region. Pre-pupal larvae will go into dormancy if the weather dips and will overwinter in their mud nests. It is a wasp-eat-wasp world out there; daubers are eaten by other parasitic wasps.

Daubers are often removed because of a cultural anti-wasp hysteria. Daubers rarely sting humans. But don’t worry if they do. While their venom may be paralytic for spiders, it is reported that a dauber sting is only mildly painful—like that of a honeybee—as it is not a typical defense mechanism. Dauber mud nests are also removed because some think they are unsightly. To each their own, but these authors enjoy their architectural creations. And we are not alone. Other wasp weirdos report that you can encourage nest creation by providing a nice muddy material for the daubers. (Not all locations are good, however, as daubers have caused plane crashes by building their nests in airplane instruments.)