Chalybion californicum is the name of the metallic blue black wasp. Both male and female feed on nectar and they are easily spotted on blooming plants like thimblehead (Hymenothrix wislizeni). The female, however does all the nest building…well, she finds the old nests of Sceliphron cementarium, the narrow waist wasp and refurbishes them to her liking. So it’s Ms. Sceliphron that builds the original mud cells and Ms. Chalybion remodels and adds additions, not to mention stunned spiders for her offspring to eat. That’s pretty cool.
When I followed these wasps around the barn I realized that they were also searching for spiders and there are plenty. So the barn not only offers a place for the mud nests, but also a hunting ground. Oh, I should point out that these mud daubers are not aggressive so I’m not afraid of getting chased or stung. Maybe if I had four more appendages I would worry, but I’m also too big to stuff in a mud cell.
Both of these wasps are in the insect order Hymenoptera, which is one of the largest insect orders in the world. It includes bees, wasps, ants and saw flies. If you want to learn more about Hymenoptera I recommend the book Bees, Wasps and Ants by Eric Grissell. What a wonderful author. The book is so readable for novices like myself, and no you may not borrow my copy.
The photos of the mud nests are mine. For photos of the two species that I jabber about please check out Bug Guide on line.