Tetraneura, Hartig, 1841

Watanabe, Tomoko, Lee, Wonhoon, Sano, Masakazu, Murakami, Keisuke & Akimoto, Shin-Ichi, 2022, Taxonomic revision of the Tetraneura akinire species group (Insecta, Aphididae, Eriosomatinae), with description of a new species and a correction of a nomenclatural confusion, Zootaxa 5183 (1), pp. 162-186 : 163-164

Tetraneura nigriabdominalis ( Sasaki, 1899) and T. akinire Sasaki, 1904

An aphid species attacking upland rice was described under the name Schizoneura nigriabdominalis by Chujiro Sasaki (1899), who reported that this species forms large colonies, including apterous adults, in early July on the roots of upland rice in Tokyo.Alate adults were observed on the roots in early August. The life cycle and the primary host plant were not mentioned, and the morphology of the apterous and alate adults was described with figures. The type specimens are considered to be lost. Later, Tanaka (1961) transferred this species to Tetraneura , resulting in the combination T. nigriabdominalis . In the revision of Tetraneura by Hille Ris Lambers (1970), T. nigriabdominalis was redescribed with a neotype designated based on a specimen collected from the roots of Oryza sativa in Tochigi Prefecture, Japan. In the revision, Hille Ris Lambers divided this species into four types: first, the gall generation on Ulmus davidiana var. japonica ; second, the root generations collected from the roots of upland rice in Japan; third, the root generations collected from grass roots in India and Indonesia; and fourth, the root generations collected from grass roots in Africa and America. Eastop & Blackman (2005) pointed out that all African records of T. nigriabdominalis as well as many of those from Asia should be referred to T. fusiformis , although a Tetraneura species collected on upland rice in East Asia was of the true nigriabdominalis .

Later, Sasaki (1904) described an aphid species that induces galls on the leaves of U. parvifolia under the name T. akinire (“ akinire ” refers to U. parvifolia in Japanese). The locality is not mentioned, but Tokyo is most likely. The type specimens also considered to be lost. Therefore, nigriabdominalis is a specific epithet of root generation, whereas akinire is for gall generation. Hille Ris Lambers (1970) treated T. akinire as a distinct species from T. nigriabdominalis based on tarsal characters of first instar nymphs of the root generations, and designated a neotype for T. akinire based on a specimen collected from a gall on U. parvifolia in Osaka, Japan. Hille Ris Lambers (1970) indicated that it is very difficult to distinguish T. nigriabdominalis from T. akinire , and that the only distinction is whether the tarsi of first instar nymphs of the root generations are either spinulose (in nigriabdominalis ) or smooth (in akinire ). However, the tarsal character is variable and does not constitute a diagnostic character (see Results and Discussion). Tetraneura akinire is currently recognized as a junior synonym of T. nigriabdominalis ( Blackman & Eastop 2021; Favret 2021).

Although the name T. nigriabdominalis has been used by many authors for a long time when referring to gall and root generations, the original description has rarely been checked by researchers. In this study, we examined the original description written in Japanese, and concluded that Schizoneura nigriabdominalis Sasaki, 1899 does not belong to Tetraneura , but probably to Anoecia .

The original description of S. nigriabdominalis indicates that nymphs produced by apterous adults have red compound eyes and 6-segmented antennae, and that the alate adults have the third “oblique veins” (= media) forked in the fore wings. None of these characters were consistent with those of Tetraneura spp. ( Hille Ris Lambers 1970; Heie 1980; Foottit & Richards 1993). In addition, the proportions of the antennal segments in apterous and alate adults in the figure are different from those of Tetraneura spp. An alate female depicted in the figure has a blackish posterodorsal abdominal patch, which is usually seen in the alate females of Anoecia spp. (“ nigriabdominalis ” is probably named after the blackish abdominal patch). The figure shows that the apterous adult has a pleural transverse dark band on each thoracic and abdominal segment, which is not seen in exule adults of Tetraneura spp. Furthermore, in Tetraneura species, it is difficult to collect a number of alate females from the roots of the secondary host in August. These lines of information clearly indicate that Schizoneura nigriabdominalis Sasaki, 1899 does not belong to Tetraneura , so the name T. nigriabdominalis should be discarded as an incorrect combination. Matsumura (1917a) treated Schizoneura nigriabdominalis Sasaki, 1899 and S. fulviabdominalis Sasaki, 1899 as synonyms of Anoecia corni , which was later treated as A. fulviabdominalis . Tanaka (1957), however, stated that Schizoneura nigriabdominalis Sasaki, 1899 appears to be the same species as Byrsocrypta ulmi L., and then in Tanaka (1961) nigriabdominalis was erroneously transferred to Tetraneura .

Therefore, the name T. akinire Sasaki 1904 was revived for the species that induces galls on U. parvifolia . Tetraneura akinire Sasaki, 1904 is a valid name and a senior synonym of T. fusiformis Matsumura , T. hirsuta (Baker) , and T. chinensis Mordvilko. However , it is still unknown whether a Tetraneura species that induces galls on U. davidiana and attacks the roots of upland rice and other gramineous species is T. akinire , and this problem is dealt with in the next section.

Tetraneura hirsuta was described based on specimens from the roots of rice in the Philippine Islands, while T. chinensis was described from galls on an Ulmus species in China. Mordvilko (1935) treated T. chinensis as a synonym of T. hirsuta , which was later treated as a synonym of T. nigriabdominalis (= T. akinire sensu novo) by Eastop & Hille Ris Lambers (1976).