Dryocosmus Giraud, 1859

Melika, George, Nicholls, James A., Abrahamson, Warren G., Buss, Eileen A. & Stone, Graham N., 2021, New species of Nearctic oak gall wasps (Hymenoptera: Cynipidae, Cynipini), Zootaxa 5084 (1), pp. 1-131 : 83

Dryocosmus Giraud, 1859

In their review of world Cynipini genera, Melika & Abrahamson (2002) indicated that this Holarctic genus contained 24 species. Since then membership of this genus has more than doubled, primarily through descriptions of many new species from Asia but also through a small number of new species from the Western Palaearctic and Nearctic ( Azizkhani et al. 2006; Tavakoli et al. 2008; Buffington & Morita 2009; Melika et al. 2010, 2011; Ide et al. 2013; Abe et al. 2014a,b; Ide & Abe 2015; Zhu et al. 2015; Tang et al. 2016; Cerasa et al. 2018; Pang et al. 2018; Nicholls et al. 2018b; Matsuo et al. 2021). Many of these new species gall Quercus section Cyclobalanopsis and section Cerris oaks as well as related Fagaceae genera. Given the rarity of host plant shifts among oak gall wasp lineages ( Stone et al. 2009), this diversity of host plants implies Dryocosmus consists of multiple lineages and requires extensive taxonomic revision, a point first raised by Melika & Abrahamson (2002) and supported by recent phylogenetic work showing this genus to be polyphyletic ( Nicholls et al. 2018b; Nieves-Aldrey et al. 2021). However, such a revision is beyond the scope of the current descriptive work.

Burks (1979) listed 17 species of Dryocosmus Giraud from America north of Mexico. Previously, Dailey (1969) had moved one species to Callirhytis , C. attractans ( Kinsey, 1922) which was recently moved to the genus Kokkocynips ( Nieves-Aldrey et al. 2021) , while Dailey & Sprenger (1973a) returned one species to Andricus , A. gigas Kinsey, 1922 where it had originally been described. More recently, three new species were described from California that induce galls on the non-oak Fagaceae genus Chrysolepis : D. rileypokei Morita & Buffington, 2009 , D. demartinii Melika, Nicholls & Stone, 2018 and D. juliae Melika, Nicholls & Stone, 2018 ( Buffington & Morita 2009; Nicholls et al. 2018b); when combined with the previously described D. castanopsidis ( Beutenmueller, 1917) this brings to four the number of species known from this non-oak host plant genus (mentioned in Burks (1979) under its old genus name Castanopsis ). Recently four Nearctic oak-associated Dryocosmus species were transferred to Kokkocynips : K. rileyi ( Ashmead, 1896) , K. imbricariae ( Ashmead, 1896) , K. coxii ( Bassett, 1881) , and K. deciduus (Beutenmueller, 1913) ( Nieves-Aldrey et al. 2021) . Thus, currently 14 species of Nearctic Dryocosmus are known, and one additional new species, D. archboldi Melika & Abrahamson , is described herein.