Badger Tracks

By Anita Carpenter

Tale of Two Wasps

     Nature is endlessly fascinating with so many organisms to study. Sometimes, these studies reveal unexpected surprises. In the September 2023 issue of the Lake Flyer, I chronicled my observations of the 1-1/4 inch long, black and yellow mud dauber wasps, Sceliphron caementarium, that were collecting mud for their nests.

     This wasp is classified in the insect order, Sphecidae, known as the thread-waisted wasps. These wasps are easily identified by the obvious thin, long petiole or stalk that connects the thorax with the abdomen. Common names for many of the thread-waisted wasps include the phrase "thread waisted wasp," but not always. This column is about two thread-waisted wasps called mud daubers.

     A female black and yellow mud dauber gathers tiny balls of mud from a mud puddle to use in the construction of her mud nest which she frequently attaches to a building. She makes many round trips to gather mud. She eventually hollows out one or more cells in the mud nest. When a cell is completed and ready for occupancy, she gathers spiders to place in the cell. She lays one egg on the first spider captured and places it in the bottom of the cell. When she is finished provisioning that cell, she seals it with mud and begins work on another cell.

     Since my first encounter with black and yellow mud daubers, I've noticed beautiful, dark metallic blue thread-waisted wasps meandering through my butterfly garden. This 3/4-inch insect pauses every now and then to nectar on flowers. This thread-waisted wasp is the common blue mud dauber, Chalybion californicum. While researching the life history of this new wasp, I was surprised to learn the relationship between these common blue mud daubers and the black and yellow mud daubers.

     Black and yellow mud daubers collect mud to build nests. Common blue mud daubers do not build mud nests. Instead, females search for old mud nests with cells that are usually those of black and yellow mud daubers. When she finds an old nest, she cleans out the old contents in a cell. She does not collect mud but collects water that she uses to soften the mud in the nest. She then reuses the softened mud to fit her own needs.

     Like the nest's previous occupant, she scavenges to find spiders. She lays one egg on a subdued spider before placing it in the cell. She adds more spiders before sealing the cell.

     Both of these thread-waisted wasps are solitary nesters and non-aggressive. They are beneficial insects--garden predators and pollinators. Common blue mud daubers are more common out west where they are well-known predators of black widow spiders.

     This past mid-June, common blue mud daubers were frequent visitors to my butterfly garden. I also noticed about 30 of them flying around a shrub--like a swarm of insects. I wondered why they would gather in this manner because they are considered solitary wasps. I could not find any references or observations about this behavior, but it was mesmerizing to watch.