Dryocosmus rileypokei

Hosts: Chrysolepis chrysophylla

[See page 20 of the pdf for color photos of these galls]

Asexual generation galls develop in axillary buds (Figs 82–85). Galls are typically ovoid, occasionally more
spherical, narrowing towards the point of attachment with the host plant at the base of the gall; approximately 8–9 mm in diameter. The gall surface is textured, with scattered pubescence or small raised bumps (similar to the catkin galls of D. castanopsidis); brownish-purple in colour. As the gall matures, an air space develops between the larval cell and surrounding parenchyma tissue, although the larval cell is never completely free. Galls are quite similar to those of D. demartinii and are induced on the same part of the plant as that species, but are more ovoid in shape, have a textured surface and develop an air space around the larval cell when mature.

Biology. Alternating sexual and asexual generations are known. Sexual galls in fruit were collected from July to the first half of September. Adults emerged under laboratory conditions soon after collection. Asexual bud galls develop during late summer/autumn, are mature by October, and fall to the ground to overwinter. Adults emerge the following spring. A proportion of asexual larvae have an extended period of diapause and emerge in early spring two years after galls were induced.

Distribution. USA, California

- James Nicholls, John DeMartini, George Melika, Graham Stone: (2018) New species of Dryocosmus Giraud gallwasps from California (Hymenoptera: Cynipidae: Cynipini) galling Chrysolepis Hjelmq.(Fagaceae)^©