You might see a black and yellow flying insect and instinctively back away. The Black and Yellow Mud Dauber may have the cautionary coat coloration of its wasp kin but this is a less aggressive branch of the family tree. You certainly don’t want to get too chummy with them but they might not be as big a threat as you think.
Mud Daubers are typically solitary wasps, meaning they don’t build large hives or live in massive colonies. They aren’t the pest control problem that something like a yellow jacket or hornet could be. Their small nests are usually defended with the vigor their cousins tend to employ and Mud Dauber stings are fairly rare.
The female is actually a rather ingenious little architect and an avid hunter of spiders. This plentiful and wide-spread food source has ensured the Mud Dauber’s success as a species. She is also responsible for building the small nests that house her young and often offend the eye of homeowners.
Nests are only about the size of your fist and only used for the hatching of one set of young. (Once they hatch, the Mud Dauber won’t use it again but other insects will soon move in if it’s left unattended.) These nests are ugly affairs. They look like a wad of mud that was unceremoniously hurled and adhered to the eaves of a house or any sheltered overhang.
She rolls up a ball of mud and sticks it to her chosen location, fashioning a substrate the she then build up into a three-dimensional “cell” for one of her eggs. Each load of mud she carries is made into an arch which will meet its mate from opposite sides of the cell. Then she hunts. She’ll paralyze – but not kill – a few spiders and stick them in the cell. She’ll then lay her egg on top and seal the chamber with more mud. The spiders will stay “fresh” and serve as food for the developing larvae. She’ll make more chambers as needed and then cover the whole grouping in a final daubing of mud.
It’s during this time that the females are a little less amicable than usual. Like any mother, they are protective of their home and offspring even though they will leave both without supervision once construction is complete. The young will hatch, eat their stored meals, overwinter in their protected home and eventually chew their way out of their chambers in the spring to repeat the cycle of life once more.
These probably don’t necessitate an emergency call to your outdoor pest control company. Leave the female alone as she builds and you’ll avoid a painful sting. If you can’t stand the muddy wad on your house, you can just knock it down and/or use a garden hose to rinse the dried mud away. Mud Daubers are quite vulnerable at this stage and easy to kill. If you don’t mind the unattractive nest, they will help control your spider population and give you a green pest control solution to a bigger problem!