The distinctive mud structures found attached to sheltered surfaces are the nests of mud daubers, a common type of wasp belonging to the families Sphecidae and Crabronidae. These insects are recognizable by their long, slender bodies and the narrow, thread-like waist connecting the thorax to the abdomen. Mud daubers are solitary and generally non-aggressive, stinging only if directly threatened or mishandled. The presence of these nests often causes confusion for observers who assume they house a large, active colony of adult wasps, similar to yellow jackets or hornets.
Solitary Lifestyle and Adult Occupancy
The answer to how many mud daubers live in a nest is straightforward: zero adults live there permanently. Mud daubers are solitary wasps, meaning they do not form social colonies with queens and workers. The entire nest structure is the work of a single mated female, who builds it as a nursery for her young.
The female constructs the nest and provisions it before sealing it off. She never stays inside to guard the developing larvae, instead moving on to build another nest elsewhere. Once the female has finished laying eggs and sealing the last cell, she leaves the structure entirely.
The Contents of the Mud Nest Cells
The mud nest is a collection of cylindrical chambers, or cells, constructed side-by-side or in a pipe-like fashion, depending on the species. Each cell is specifically provisioned by the female to sustain one developing larva. The female hunts spiders, or sometimes other insects, which she paralyzes with a sting before packing them into the cell.
The venom from the sting does not kill the prey but keeps it alive and fresh until the larva is ready to feed. A single egg is laid on one of the paralyzed victims inside each sealed chamber. The number of cells varies significantly depending on the size of the overall mud structure and the species, often containing anywhere from a few to twenty-five cells in one mass.
Once the cell is completely stocked with paralyzed prey, the female seals it with a mud cap. This cap protects the contents and ensures the offspring can develop undisturbed.
Emergence and Nest Abandonment
The life cycle within the cell begins when the egg hatches into a larva. This larva immediately starts feeding on the paralyzed spiders, consuming the stored food over a period that typically lasts a few weeks. Once the larva has finished eating, it spins a silken cocoon and enters a pupal stage.
In most regions, the pupa will remain dormant inside the sealed mud cell throughout the winter months, a process known as overwintering. Development is completed the following spring when the adult mud dauber emerges. The new adult chews a perfectly round hole through the mud wall to exit the structure and begin its life.
Once the new adult has departed, the nest has fulfilled its purpose and is considered inactive. Finding a mud nest with one or more small, round holes indicates that the occupants have successfully emerged and the structure is now empty. These inactive nests are not defended and remain attached to the surface until they degrade or are removed.