Dryocosmus demartinii, new species

Gall (Figs 14–17) [see page 8 of the pdf for these color photos]. A roughly spherical axillary bud gall found on shoots of the same year, approximately 6–7 mm in diameter. Superficially similar to asexual gall of D. rileypokei, but typically smaller and rounder with smooth surface. Gall surface is smooth; purple in colour in growing galls turning yellow-brown in mature galls. The gall remains solid as it matures, with no air space between the larval cell and surrounding parenchyma tissue.

Biology. Only asexual females are known, inducing bud galls on Chrysolepis chrysophylla which develop from late summer. Galls are mature by September/October and fall to the ground to overwinter. Under laboratory conditions adults emerge the following year in summer.

Distribution. USA, California.

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).