Dryocosmus minusculus

This cynipid wasp induces tiny, 1 mm wide pumpkin-shaped galls on the upper surface of leaves of all species in the black oak group.

Hosts:
Coast live oak (Quercus agrifolia)
Interior live oak (Quercus wislizeni)
California black oak (Quercus kelloggii)

Dryocosmus minusculus

Quercus agrifolia, wislizeni, kelloggii
Leaf galls, detachable
Brown buttons with a minute pit in the center above, dropping when mature. On upper of side leaf. Fig 111. Diameter 2.5 mm.

Fig 111 Q-agrifolia, wislizeni and rarely on kelloggii. Occur in fall on upper side of leaf, dropping when mature. Said to be so numerous some years as to defoliate a tree. Some years not common. Adults out Apr. 17 (Mt. Diablo). The guest fly, Synergus agrifoliae Ashm. often reared from it, varies in color pattern and has been described as Synergus maculatus Full. and as nergus obscurus McC. & Egb.

DRYOCOSMUS MINUSCULUS, new species

Host. — Quercus agrifolia.

Gall (pl. 17, fig. 13) . — Small brown galls up to 2.7 mm. in diameter, shaped like a depressed sphere with a minute pit in the center above. Produced on upper side of leaves of Quercus agrifolia, Q. wislizeni, and rarely on Q. kelloggii in the fall and dropping when mature. Said to be so numerous sometimes as to defoliate the tree. Some years these galls are not common.

Habitat. — The types were reared from galls collected October 22, 1939, on Quercus agrifolia on Mount Diablo, Calif. Adults emerged April 17, 1941. Galls have been noted on this host at some 40 localities between Alpine and Ukiah and Red Bluff, Calif. They are also common on Quercus wislizeni and have been seen on Quercus kelloggii a few times. The guest fly, Synergus agrifoliae Ashmead, often reared from it, varies much in color pattern and has been redescribed as Synergus maculatus Fullaway (1911) new synonymy, and as Synergus obscurus McCracken and Egbert (1922), new synonymy.