Black and yellow mud daubers (Hymenoptera: Sphecidae: Sceliphron caementarium) can be found throughout North America, often in proximity to humans. These industrious wasps collect mud to build their nests, typically securing them on hard, sheltered surfaces. While rocky outcrops suit this need in the wild, buildings can be even more attractive. Their dried mud nests can often be seen under eaves and porches since these man-made features provide the substrate and protection they require.
As a female builds her multi-chambered nest she paralyzes and transports spider prey to each cell. After laying an egg in a provisioned cell she seals it off with a mud plug. When the egg hatches the larva has a stockpile of spiders to eat. After pupating and overwintering in the nest, the new adult eventually emerges the following spring. While the larvae eat spiders that are provided by their mothers, the adults visit flowers for food.
Although the presence of these wasps and their nests around homes can be unsettling for some people, they generally don’t present a threat. Mud daubers are solitary and are rarely aggressive…unless you’re a spider.