Dryocosmus rileypokei (sexgen)

Dryocosmus rileypokei Morita & Buffington, new species

Hosts: Chrysolepis sempervirens

Description of nut damage.—Damage contained within nuts (c.f., Fig. 2F); lateral aspects of base of nut pericarp bulged slightly and mesocarp layer relatively thick when compared with undamaged nuts; larval chamber circular in cross-section and found within the mesocarp layer (GC, Fig. 2E; also visible in Figs. 2B–D; also see diagram, Fig. 3), seed (=endosperm and embryo; S, Fig. 2A) missing in infested nuts; exit hole of adult usually located near equa- tor of nut, occasionally at base of nut.

Biology and distribution.—Dryocosmus rileypokei is set apart from other Cynipini as a nut galler on Chrysolepis sempervirens. In all C. sempervirens nuts examined, the gall is within the mesocarp layer of the lower one-half of the nut, expanding the walls of the nut slightly, resulting in a gentle bulge, and are presumed to have acquired nutritional resources normally sent to the developing seed. Emergence holes usually were located along the side of the nut (Fig. 2E) or at its base. In one nut examined, three adult wasps (dead) were removed, indicating that each nut can support more than one adult wasp. The distribution of this wasp is probably coincident with Chrysolepis sempervirens, which can be found throughout the Sierra Nevada and Cascade ranges of CA, NV, and southern OR (McMinn 1939).

Not all oak gall wasps gall oaks: the description of Dryocosmus rileypokei, a new, apostate species of Cynipini from California