The adult wasps are small, stout and brown, about 5 mm long with clear wings nearly twice the length of the body.

[5] The adult female lays eggs in the cambium layer of oak twigs during the fall using her ovipositor.

The larvae pupate and then bore their way out of the gall in late summer or early fall and fly off to lay eggs in other trees.

The cynipid gall-inducer induces galls of 5-20 cubic centimeters on the twigs of the valley oak (Quercus lobata), an endemic tree in California.

[7] The native range of these gall wasps spans from most of California (extremes of southern Washington) to northern Mexico.

Many of the benefits of induced galls include nutrition, a refuge from natural enemies, and a consistent environment with controlled abiotic factors.

According to recent findings, experimental manipulation of abiotic factors (i.e., relative ambient humidity) indicated that A. quercuscalifornicus larvae modify the internal environments of galls, thereby, supporting the microenvironment hypothesis.

The large galls produced by A. quercuscalifornicus may aid in the protection against other parasitoids however, this can also led to increase predation from avian species.

[12] The moist conditions created in the internal microclimate of galls can also led to increased chance of fungal infection.