Extremely tiny (1-2 mm) red/bright-orange colored ants. Displaced a colony of Camponotus novaeboracensis.
These were under a board. They were in various sizes. Roughly carpenter ant sized.
Maybe Spilosoma. Hanging out on in the open, between oak woodland and a grassy opening.
On poison oak in redwood-Douglas fir forest.
I think this may be in the genus Dasymutilla.
On Gentiana affinis v. ovata
Photographed at Abbott's Lagoon, Pt. Reyes National Seashore, Marin County, California