Chalybion californicum

Females can build their own nests, but often refurbish nests abandoned by other wasps and bees,^[4] particularly those of Sceliphron caementarium,^[5] removing any spiders captured by S. caementarium and the larva, replacing it with an egg of its own and freshly caught spiders.^[3] They go through multiple generations in a year.^[2]

This species is most famous for its predation of black widow spiders.^[2] Adults feed on the nectar of flowers, which powers their flight. They pollinate some common wildflowers, including Berberis vulgaris, Daucus carota, and Zizia aurea. Larvae are fed spiders, often Latrodectus mactans. They prefer to hunt prey on the ground or under rocks.^[4]