Tremex bicinctus Shinohara 2023, n. sp.
Creators: name: Shinohara, Akihiko
Publisher: name: Zenodo
Year: 2023
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Hymenoptera
Siricidae
Tremex
Tremex bicinctus

description: Tremex bicinctus Shinohara, n. sp.
(Figs 3B, 5B, 7B–D, 10B, 11A, 13; Tables 1, 2, 4)
Tremex sp., Kawamoto, 2010: 168; Sugimoto & Sono, 2013: 114; Tanaka, 2015: 38; Saito & Shirota, 2016: 78.
Description. Female (holotype: Figs 3B, 5B, 7B, 10B, 11A). Length without ovipositor about 21 mm. Head black, with large brown spot on gena. Mandible black. Antenna black, with scape, pedicel, basal 3/4 of flagellomere 1, apex of flagellomere 11 and entire flagellomere 12 pale brown. Thorax entirely black. Legs black, with tibiae and tarsi dark reddish brown to black; basal half of each tibia and hind tarsomere 1 creamy white. Wings distinctly infuscated with blackish brown; forewing with small parts of cells 1Rs, 1M, 2M and posterior parts of cells 1Cu and 2Cu almost clear hyaline (Fig. 7B); hindwing with basal half (except for its narrow base) almost hyaline. Abdomen black, with following pale brown: tergum 2 (except very narrow anterior and rather broad posterior margins), narrow anterior margin of tergum 3, mark near anterior lateral margin (but not including spiracle) of terga 4–7, anterior half (but not including narrow anterolateral area around spiracle), small elongate spot on lateral surface of tergum 9, and cornus (apically blackish); sterna creamy white, except for posterolateral parts; ovipositor sheath blackish reddish brown.
Antenna (Fig. 5B) with 14 antennomeres, flagellomere 6 about 0.79 times as long as wide. Pronotum (Fig. 3B) with MPL about 0.75 times as long as OOCL. Hind tibia about 1.01 times as long as hind tarsomere 1; dorsal margin of hind tibia straight or very shallowly concave. Forewing about 1.4 times as long as ovipositor sheath. Abdominal tergum 8 about 1.18 times as long as terga 5–7 combined; precornal basin short, its length about 0.67 times as long as wide, widest at middle (Fig. 11A); ovipositor sheath about 2.59 times as long as apical sheath.
Male. Unknown.
Variation. The six specimens examined vary from 20 to 24 mm in length without ovipositor and show the following variation in color pattern. In pale specimens, the tergum 7 has the narrow anterior margin pale brown, the tergum 9 has a large pale brown spot laterally and in the anterior part of the precornal basin, and the apical ovipositor sheath is pale yellowish brown basally, blackish medially and reddish brown apically. The structural characters vary as follows: Antenna with 14 or 15 antennomeres. Pronotum with MPL 0.69–0.83 (average 0.76) times as long as OOCL. Hind tibia 1.01–1.06 (average 1.04) times as long as hind tarsomere 1. Forewing 1.33–1.40 (average 1.36) times as long as ovipositor sheath. Abdominal tergum 8 0.92–1.27 (average 1.10) times as long as terga 5–7 combined; precornal basin 0.62–0.72 (average 0.67) times as long as wide; ovipositor sheath 2.59–2.73 (average 2.67) times as long as apical sheath.
Type material. Holotype: ♀, Japan, Honshu, Yamaguchi Pref., Daido, Hôfu-shi, 19–26. V. 2009, H. Sugimoto (NSMT, cited by Kawamoto 2010). Paratypes: JAPAN: HONSHU: Chiba Pref.: 1♀, Bôsônomura, Ryûkakuji, Sakae-machi, Inba-gun, 18. VI. 2016, C. Shirota (YS, cited by Saito & Shirota 2016). Yamaguchi Pref.: 1♀, same data as holotype (NSMT, cited by Kawamoto 2010); 1♀, Hara, Daido, Hôfu-shi, 29. V. –5. VI. 2012, H. Sugimoto (NSMT, cited by Sugimoto & Sono 2013); 1♀, Hekinaka, Nagato-shi, 1–12. VI. 2012, H. Sugimoto (NSMT, cited by Sugimoto & Sono 2013). KYUSHU: Fukuoka Pref.: 1♀, Kanetsukiyama, 33.563N 130.265E, 200m, Myôbaru, Nishi-ku, Fukuoka-shi, 9. VI. 2020, K. Nishiya (NSMT).
Distribution (Fig. 13). Japan (Honshu, Kyushu).
Host plant. Fagaceae: Quercus serrata Murray (Saito & Shirota 2016).
Etymology. The new specific epithet refers to the two banded abdomen of the new species.
Remarks. This new species is well characterized by the dark color pattern as described above and will be distinguished from the other Japanese congeners by the characters given in the key.
In Maa’s (1949) key to the Old World species, this species runs to Tremex temporalis Maa, 1949, which was described from a female specimen from “Chekiang: W. Tien-Mu-Shan”, eastern China. It differs from T. bicinctus in the following features (abstracted from the original description by Maa (1949), who used different terminology): antenna “13 segmented”; relative lengths of antennomeres 3 and 5 as 9:10; scutellum [=mesoscutellum] with two lateral yellow streaks; femora III [=hind femur] chestnut brown; forewing hyaline, infuscated in apical portion of cell bm [=cell R], basal portions of cell lm [=cell 1Rs] and apex of the forewing; cell 2r [=cell 2R1] tinted with brownish; cell Ir [=cell 1R1] and “stigmata” yellow; abdominal tergite VIII [=tergum 8] subapically with a narrow, transverse, yellow band crossing the precornal basin; forewing/ovipositor [ovipositor sheath] ratio 1.27; ovipositor [ovipositor sheath]/sawsheath [apical sheath] ratio 2.59. In T. bicinctus, the antenna (Fig. 5B) has 14 or 15 antennomeres, the relative lengths of the antennomeres 3 and 5 are as 13–15:10 (n=6), the mesoscutellum is entirely black (Fig. 3B), the hind femur is black, the forewing is dark infuscated, with parts of the cells 1M, 1Rs, 2M, 1Cu and 2Cu hyaline and the stigma is pale brown or dark brown (Fig. 7B–D), the abdominal tergum 8 is all black in apical half (Fig. 10K, L), the forewing/ovipositor sheath ratio is 1.33–1.40 (average 1.36) and the ovipositor sheath/apical sheath ratio is 2.59–2.73 (average 2.67).
In the key to the Chinese species by Xiao & Wu (1983) and Xiao et al. (1992), T. bicinctus may go to T. abei Togashi, 1980, though the body length, which is used to separate the two species in the couplet 11 (couplet 12 in Xiao et al. 1992), is subject to large variation. From T. abei, T. bicinctus differs in the much darker color pattern (namely, mostly black head and entirely black mesoscutellum and precornal basin, largely dark infuscated forewing, Figs 3B, 7B–D, 10B) and the antenna with 14 or 15 antennomeres (Fig. 5B). Tremex gongliuensis Xiao & Wu, 1983, from Xinjiang may also resemble T. bicinctus in general color pattern, but the former species has the pronotum very short (MPL about 1/2 as long as OOCL) and the pronotum and the mesoscutellum marked with reddish brown.
Judging from the description and figures in Lee et al. (1998), T. nigrocephalus from Korea, looks similar to T. bicinctus in color pattern, but T. nigrocephalus has the pronotum long (MPL subequal to OOCL, as in T. contractus), the forewing with more hyaline areas (fig. 3K in Lee et al. 1998), the tergum 8 “excessively long, about as long as four preceding segments combined”, and the precornal basin 0.55–0.59 times as long as wide. Tremex bicinctus has the pronotum short (MPL 0.69–0.83 (average 0.76) times as long as OOCL), the forewing largely dark infuscated (Fig. 7B–D), the tergum 8 0.92–1.27 (average 1.10) times as long as the preceding three segments combined and the precornal basin (Fig. 11A) 0.62–0.72 (average 0.67) times as long as wide.
Tremex incognitus Háva, 2021, recently described from Vietnam, also resembles T. bicinctus. The former species has brownish areas on the head, thorax and anterior part of precornal basin and pale orange area in the anterior part of the cell 3R 1 in the forewing (Háva 2021). In T. bicinctus, the head, thorax and the precornal basin are all black (Figs 3B, 10B), except for a spot on the gena, and the cell 3R1 is entirely dark infuscated (Fig. 7B–D).
E: early, or 1 to 10. M: middle, or 11 to 20. L: late, or 21 to 30 or 31. *Reared specimens are not included.
It should be noted that each of the five species discussed above is known only from one or a few specimens from distant localities in East Asia and the specimens of these species were never directly compared. We need more material and studies of the type material to clarify the relationships of these seemingly closely related taxa.
description: Published as part of Shinohara, Akihiko, 2023, The woodwasp genus Tremex (Hymenoptera, Siricidae) of Japan, pp. 1-40 in Zootaxa 5239 (1) on pages 14-22, DOI: 10.11646/zootaxa.5239.1.1, http://zenodo.org/record/7621749