Syzeuctus nigrus Watanabe & Riedel, 2024, sp. nov.
Creators: name: Watanabe, Kyohei
name: Riedel, Matthias
Publisher: name: Zenodo
Year: 2024
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Hymenoptera
Ichneumonidae
Syzeuctus
Syzeuctus nigrus

description: Syzeuctus nigrus sp. nov.
(Figs 1 H, 2 J, 15 A–G, 16 A–C)
Type series. Holotype: F, JAPAN, Amamioshima Is., Kagoshima Pref., Mt. Yui-dake, 15. VII. 2004, H. Makihara leg., MsT (KPMNH). Paratypes: JAPAN: [Honshu] 1 F, Chiba Pref., Shiroi City, Shiroishi-undou-koen, 30. IX. 2012, Y. Saito leg. (KPMNH); 1 M, Kanagawa Pref., Yokohama City, Enkaizan, 5. X. 2008, K. Kubo leg. (KPMNH); [Izu Isls.] 1 F, Tokyo, Izuoshima Is., Motomachi, Mt. Omaru-yama, 17. VIII.–5. X. 2012, K. Tsujii leg., MsT (KPMNH); [Awajishima Is.] 1 M, Hyogo Pref., Sumoto, Uchida, 22. IX. 2002, S. Ohkusa leg. (KPMNH); [Shikoku] 1 F, Ehime Pref., Kumakogen, Yurano, 20. VIII. 2007, E. Yamamoto leg., MsT (EUM); 1 F, Ehime Pref., Kihoku Town, Narukawa valley, 15. VII. 2006, M. Nishikawa leg., at light (EUM); [Tsushima Is.] 1 F, Nagasaki Pref., Izuhara Town, Mt. Ariake, 22–23. VII. 1979, I. Kanazawa leg. (NARO); [Amamioshima Is.] 1 F, Kagoshima Pref., Sumiyou Town, Nr. Santaro-toge, 4. VI. 2007, K. Watanabe leg. (KPMNH); [Okinawajima Is.] 2 F, Okinawa Pref., Kunigami Vil., Oku, 13. VI. 2003, H. Makihara leg., MsT (1 F: KPMNH; 1 F: ZSM); 1 F, ditto, 10. VII. 2003 (KPMNH).
Description. Female (n = 10). Body polished and covered with punctures and silvery setae; length 8.5–10.5 (HT: 10.4) mm. Setae on head and mesosoma not exceptionally long and erect.
Head 0.55 × as long as wide. Combined length of clypeus and face 1.05–1.15 (HT: 1.05) × facial width. Clypeus sparsely punctate ventrally, densely punctate dorsally, slightly convex in lateral view, without central transverse ridge. Face densely punctate, slightly convex medially in lateral view, without a pair of convexities just above of each anterior tentorial pit. Frons slightly concave, without horns or convexities. Malar space 0.6–0.7 (HT: 0.7) × as long as basal mandibular width. Genal carina lamella-like ventrally, reaching mandibular base. POL 1.2–1.5 (HT: 1.3) × as long as OD. OOL 1.0–1.1 (HT: 1.0) × as long as OD. Temple weakly roundly narrowed behind eye in dorsal view (Fig. 15 D). Antenna with 38–40 (HT: 40) flagellomeres. FL I 4.0–4.25 (HT: 4.1) × as long as maximum depth in lateral view and 1.8–1.85 (HT: 1.85) × as long as FL II. Preapical flagellomere 1.0 × as long as maximum width.
Mesosoma coarsely and densely punctate, 1.4–1.45 (HT: 1.45) × as long as maximum height. Pronotum with small smooth area just behind of epomia. Epomia present, its dorsal end not reaching dorsal margin. Mesopleuron densely punctate ventrally, sparsely punctate dorsally; speculum with a large smooth area, its lower area concave (Fig. 15 E). Epicnemial carina present latero-ventrally and ventrally, its dorsal end remote from anterior margin of mesopleuron, without angulation (Fig. 1 H). Dorsal surface of propodeum with transverse rugae. Posterior transverse carina of propodeum present and complete (Fig. 15 F). Fore wing length 7.0–8.0 (HT: 7.5) mm. Areolet receiving vein 2m-cu slightly basal to the outer angle, petiolated anteriorly; petiole as long as areolet (Fig. 15 G). Fore wing vein 1cu-a subvertical, slightly postfurcal to vein M&RS. Nervellus reclivous, intercepted posterior to the middle. Hind femur 5.25–5.7 (HT: 5.4) × as long as maximum depth in lateral view. Ratio of length of first to fifth hind tarsomeres 4.0–4.2 (HT: 4.2): 2.0: 1.35–1.4 (HT: 1.4): 0.6: 0.7–0.8 (HT: 0.7). Hind tarsal claws pectinate by short teeth, moderately bent apically (less than 90°) (Fig. 2 J).
Metasoma. T I 1.6–2.0 (HT: 2.0) × as long as maximum width, densely punctate laterally, largely smooth medially. T II 1.35–1.5 (HT: 1.5) × as long as maximum width T II and T III coriaceous with dense punctures. T IV to T V coriaceous with fine punctures. Ovipositor sheath 2.55–3.0 (HT: 2.75) × as long as hind tibia, ca. 1.1 × as long as fore wing, and shorter than body length.
Colouration (Figs 15 A–G). Body (excluding wings and legs) black. Lower part of clypeus, mandible except for teeth, malar space, W-shaped marking of face, inner orbit on frons and vertex, palpi, and outer orbit except for dorsal part yellow to ivory. Antenna blackish-brown. Collar and dorsal longitudinal stipe of pronotum yellow to ivory. A pair of antero-lateral markings and a median marking of mesoscutum, subtegular ridge, antero-dorsal and postero-ventral spots of mesopleuron, a pair of lateral spots of scutellum, postscutellum, posterior spot of metapleuron, and a posterior transverse marking of propodeum yellow to ivory. Metasomal tergites black except for a pair of basal spots of T I and posterior margins of T I to T III yellow to ivory. Posterior margins of T IV to T VII usually narrowly tinged with reddish-brown. Membranous parts of metasomal sternites ivory. Subgenital plate sometimes reddish-brown. Ovipositor reddish-brown. Wings hyaline. Apical clouded area of fore wing weakly present. Veins and pterostigma blackish-brown except for yellowish-brown wing base. Fore and mid coxae ivory apically, blackish-brown basally. Fore and mid trochanters ivory. Fore and mid legs except for coxae and trochanters reddish-brown to reddish-yellow. Mid trochantellus and tarsus more or less darkened. Hind leg blackish-brown to dark reddish-brown.Apices of coxa, trochanter, trochantellus, and femur tinged with yellowish-brown. Basal part of hind tibia and tibial spurs yellowish-brown. Apex of hind coxa sometimes with a yellow marking.
Male (n = 2). Similar to female (Figs 16 A–C). Malar space 0.8–0.9 × as long as basal mandibular width. POL 1.0–1.5 × as long as OD. OOL 1.0–1.2 × as long as OD. Antenna with 41–42 flagellomeres. FL I 3.55–4.5 × as long as maximum depth in lateral view and 1.6–1.7 × as long as FL II. Hind femur 6.0–6.1× as long as maximum depth in lateral view. Tergal spiracles not enlarged. T I 2.2–2.4 × as long as maximum width. T II 1.4–1.63 × as long as maximum width. Yellow area of body larger than female. Face yellow except for a small median longitudinal black stripe. Antenna reddish-brown apically. Fore and mid legs largely yellow. Yellow area of posterior margins of T I to T III narrower than female.
Distribution. Japan (Honshu, Izuoshima Is., Awajishima Is., Shikoku, Tsushima Is., Amamioshima Is., and Okinawajima Is.).
Etymology. The specific name refers to its black body.
Bionomics. Unknown.
Remarks. This is the first record of this genus from Ryukyu Islands (Oriental part of Japan). In the key provided by Riedel (2021), the female runs to couplet 27 (S. fuscator (Panzer, 1809)), but differs by the mesopleuron with a postero-ventral yellow marking (absent in S. fuscator), the dorsal margin of pronotum with a longitudinal yellow marking (with a triangular yellow marking in S. fuscator), the apical clouded area of fore wing weaker than S. fuscator, and the punctures of T II sparser than S. fuscator. The male of this species also resembles S. fuscator but can be distinguished by the shape of yellow markings of pronotum and mesopleuron as females and the yellow margins of T I to T IV narrower than S. fuscator.
description: Published as part of Watanabe, Kyohei & Riedel, Matthias, 2024, Revision of the genus Syzeuctus Förster, 1869 (Hymenoptera, Ichneumonidae, Banchinae) from Japan, pp. 35-71 in Zootaxa 5496 (1) on pages 57-60, DOI: 10.11646/zootaxa.5496.1.2, http://zenodo.org/record/13331013