Andricus bakkeri
Gall:
A monothalamous, cup-shaped leaf spangle, 3-3.5 mm in height. The larval cell occupies the base of the cup whose margins are collapsed at maturity. The galls appear on the leaves during the early summer months and grow rapidly until they reach full size in August. At this time the galls are red and contain small larvae. Pupation occurs in late October and early November.
Hosts:
Quercus dumosa
Quercus engelmanni
Quercus garryana
Range: La Crescenta CA
”- Robert J Lyon: (1984) New Cynipid Wasps from California (Hymenoptera: Cynipidae)©
Reference: https://www.biodiversitylibrary.org/page/56448726#page/307/mode/1up