Pleroneura hikosana Togashi, 1972

Shinohara, Akihiko, 2016, The sawfly genus Pleroneura (Hymenoptera, Xyelidae) of Japan: P. itoi n. sp. and a key to species, Zootaxa 4121 (4), pp. 495-500 : 496

Pleroneura hikosana Togashi, 1972

( Figs 1 A, B, 2A, B, G)

Pleroneura hikosana Togashi, 1972: 53 ; Shinohara, 1995: 835; Kurokawa, 1996: 8; Shinohara, 1996: 728. See Shinohara (1995) for more references.

Material examined. ♀, Uchiurayama course, Mt. Kiyosumiyama, Kamogawa, Chiba, 17. IV. 2 0 0 5, K. Kubo.

Distribution. Japan (Honshu, Kyushu).

Host plant. Unknown.

Remarks. Pleroneura hikosana was described from Mt. Hikosan, Fukuoka prefecture, northern Kyushu, Japan, based on a female holotype and a male paratype. Kurokawa (1996, published November 15) and Shinohara (1996, published December 25) independently published “the first record” of P. hikosana from Honshu, the former based on a female from Mt. Asuwayama, Fukui prefecture, and the latter based on a female from Mt. Tokusagamine, Yamaguchi prefecture, both localities in western Honshu. These four are the only specimens of P. hikosana recorded so far. The present discovery of P. hikosana in Chiba prefecture expanded the known distributional range of the species by about 370 km eastwards.

The collection sites of this species, as understood from the label data, are lower mountains. The altitude of the highest peak of Mt. Hikosan is 1199 meters, that of Mt. Tokusagamine is 989 meters, whereas that of Mt. Asuwayama is only 116 meters and that of Mt. Kiyosumiyama is 377 meters. The host plants of the Pleroneura species are Abies spp. (Ohmart & Dahlsten 1977; Blank 2002), while one exceptional species, P. piceae , is known to feed on Picea glehnii (F.Schmidt) Mast. in Japan ( Shinohara 1995). Although we still have no direct evidence, the almost only candidate for the host plant of P. hikosana is Abies firma Siebold et Zucc. This fir species is widely spread on lower mountains of Honshu, Shikoku and Kyushu ( Liu 1971) and is the only Abies species occurring at lower altitudes including both Mt. Asuwayama (Nakamura, personal communication) and Mt. Kiyosumiyama ( Kasuya & Sakura 1974). Pleroneura hikosana should probably be distributed in association with A. firma on lower mountains in Honshu, Kyushu, and probably also in Shikoku.

The Chiba female specimen ( Figs 1 A, B, 2A, G) is the largest (about 6.8 mm, excluding the valvula 3) and the darkest specimen ever known. It has most of the dorsal surface of the head black, without a reddish brown marking on the lateral part of the vertex, which is conspicuous in the previously known specimens (e.g. a specimen from Mt. Tokusagamine, Fig. 2 B).

Figures

FIGURE 1. Pleroneura spp., ♀. A, B, P. hi k o s an a, Mt. Kiyosumiyama, Chiba; C, D, P. itoi, holotype; E, F, P. piceae, Asahidake-onsen, Hokkaido; G, H, P. subulata, paratype, Meotobuchi-onsen, Tochigi.

FIGURE 2. Pleroneura spp., ♀, heads (A – F) and ovipositor sheaths (G – J). A, G, P. hi k o s an a, Mt. Kiyosumiyama, Chiba; B, same species, Mt. Tokusagamine, Yamaguchi; C, D, H, P. itoi, holotype; E, I, P. piceae, Asahidake-onsen, Hokkaido; F, J, P. subulata, paratype, Meotobuchi-onsen, Tochigi.