Andricus kingi
Small, pink, cone-shaped galls on the underside of leaves of Quercus lobata, about 5mm. high and 4 mm. across the base, which is broad and rather saucer-shaped. The outer portion of the gall is conical, the sides curved inwards slightly. The larval chamber is near the apex, where the exit hole is found.
”- DT Fullaway: (1911) Annals of the Entomological Society of America.Article: Monograph of the Gall-Making CynipidA (CynipinA) of California©
Reference: https://www.biodiversitylibrary.org/page/16270744#page/382/mode/1up