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).

Description of a New Genus for Chrysolepis-Associated Dryocosmus Species

Four species of Dryocosmus induce galls on the host plant genus Chrysolepis on the Pacific slope of North America. These form a clearly distinct clade in both StarBEAST and ML analyses (node 8; Fig. 4 and Supplementary Fig. S3), consistent with other studies that show this set of species to be allied to Heteroecus Kinsey and Grahamstoneia Melika and Nicholls, and not with other Dryocosmus taxa (Nicholls et al. 2018, Melika and Nicholls 2021).

Here we establish the new genus, Chrysolepicynips Stone, Nicholls, Melika and Tang, gen. nov. to circumscribe the four Chrysolepis-associated Dryocosmus species, with four new combinations: Chrysolepicynips castanopsidis (Beutenmuller 1917), comb. nov., C. demartinii (Melika, Nicholls and Stone 2018), comb. nov., C. juliae (Melika, Nicholls and Stone 2018), comb. nov., C. rileypokei (Morita and Buffington 2009), comb. nov. 

Distribution and biology. All Chrysolepicynips species are known only from California, and both generations induce galls on Chrysolepis (Fig. 3). Asexual generation galls are induced on buds (C. demartinii and C. rileypokei) or catkins (C. castanopsidis and C. juliae); known sexual generation galls are induced in fruit cupules (C. rileypokei) and buds, leaves, and young shoots (C. juliae) (Nicholls et al. 2018).

Dryocosmus rileypokei

Hosts: Chrysolepis chrysophylla

Gall. Sexual generation galls develop in the cupule part of the fruit (Figs 80–81). The larval chambers are
within the mesocarp tissue of the developing fruit; infested fruit do not develop seeds. A detailed description of
galls is given in Buffington & Morita (2009).

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