Here’s one for your collection. I don’t know what they are, but I think I know what they are doing. Photo was taken in Burbank, CA at a park.
These are Three Lined Potato Beetles, or Old Fashioned Potato Beetles, Lema trilineata. The term Old Fashioned is probably in reference to the increased distribution of the Colorado Potato Beetle. The Three Lined Potato Beetle feed on the leaves of plants in the nightshade family. If your park is a natural wild park, they will feed on datura and deadly nightshade. If there is a cultivated garden, they will feed on peppers, tomatoes, and eggplant as well as potatoes.