Neuroterus niger Gillette, 1888

Synonyms: Neuroterus nigrum Gillette (1888: 218), females and galls. Revised spelling by Dalla Torre and Kieffer (1902: 51).
Neuroterus papillosus Beutenmueller, 1910, syn. nov.
Neuroterus perminimus Bassett, 1900. Synonymized by Beutenmueller (1910: 121), and treated as a variety of N. niger by Kinsey (1923: 48), but synonymy ignored by Weld (1951) and later authors; syn. nov.
Kinsey (1923) described 5 additional varieties of N. niger, all inducing integral leaf galls. Four we consider as synonyms: Neuroterus niger var. arizonicae Kinsey, 1923 (asexual generation, Arizona, on Q. arizonica), syn. nov.; Neuroterus niger var. grisea Kinsey, 1923 (asexual generation, Texas, on Q. grisea), syn. nov.; Neuroterus niger var. nigripes Kinsey, 1923 (asexual generation, Texas, on Q. sinuata var. breviloba (=Q. breviloba) and Q. stellata), syn. nov.; Neuroterus niger var. pattersoni Kinsey, 1923 (asexual and sexual generations, Texas, on Q. sinuata var. breviloba (=Q. breviloba) and Q. stellata, respectively), syn. nov..

The fifth variety described by Kinsey is Neuroterus niger var. alimas Kinsey, 1923 (sexual generation, Texas, on Q. virginiana) that was still considered as form of N. niger by Burks (1979). According to Kinsey (1923) this variety induces a sexual generation spring gall, while the other four varieties induce autumn asexual generation galls. Moreover, N. niger var. alimas is the only variety associated with section Virentes oaks while the other four are on section Quercus oaks, and as mentioned in the Introduction, no Nearctic cynipid species are shared across the oak sections (Abrahamson et al. 1998a, 2003; Stone et al. 2009). Hence biological information suggests that N. niger var. alimas is a species distinct from N. niger (sensu Gillette 1888) and the other four of Kinsey’s varieties. Kinsey (1923) described N. niger var. alimas based on one female (holotype – lost) and 13 males and gave no detailed morphological description for this variety. Thus, there is no morphological evidence for synonymisation of N. niger var. alimas to N. niger while at the same time it cannot be treated as a valid species so Melika et al. (2021) moved it to nomen dubium.

Gall. The asexual generation gall is described by Gillette (1888) and are small blisters integral to the leaf blade (Fig. 181).

Biology. See Gillette (1890), Beutenmueller (1910), Kinsey (1923), and Weld (1926) for the biology of one or both generations. The minute, integral leaf galls of the asexual generation have been recorded on Q. macrocarpa. Galls became evident in Edmonton in August and matured in September. This species represents a rare case where males are present in the asexual generation. Males of the asexual generation comprised a tiny fraction of the cynipids reared from asexual generation galls, with only 62 males reared from gall collections made in Edmonton during 2004- 2006, as opposed to 20979 females. In addition, most males were reared in the autumn (October-December) of the year of gall formation, whereas almost all females emerged in April-May the following spring after gall formation. Thus, most males were temporally isolated from ovipositing females and therefore essentially functionless. This is similar to Patterson’s (1928) discovery of functionless males of the asexual generations of Neuroterus contortus (Weld, 1921) and N. quercusrileyi (Bassett, 1881). In his study, males and females co-occurred, but they appeared unwilling to mate under laboratory conditions. Galls of the sexual generation are on Q. alba, Q. bicolor and Q. macrocarpa (Gillette 1890, Burks 1979, Digweed 2010). We observed that clusters of galls (e.g., on one catkin) often produced adults of only one gender. Galls were visible in Edmonton in May, with adults emerging in late May or early June. Sexual generation females were observed ovipositing mostly on the undersides of leaves and often on leaves that were on long shoots and/or that were not yet fully mature.

Distribution. In the USA the asexual generation has been recorded from Massachusetts, Michigan, Wisconsin, Iowa (Burks 1979), Illinois, Indiana, New York, New Jersey, Pennsylvania, Ohio (Beutenmueller 1910); Arizona, Texas (Kinsey 1923), and Alberta and Manitoba in Canada. The sexual generation has been recorded from Illinois (Weld 1926), Iowa (Burks 1979), and TX (Kinsey 1923) in the USA and Alberta in Canada.

- James Nicholls, George Melika, Scott Digweed, Graham Stone: (2022) Pairing of sexual and asexual generations of Nearctic oak gallwasps, with new synonyms and new species names (Hymenoptera: Cynipidae, Cynipini)^©