Syzeuctus Forster 1869
Creators: name: Watanabe, Kyohei
name: Riedel, Matthias
Publisher: name: Zenodo
Year: 2024
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Hymenoptera
Ichneumonidae
Syzeuctus

description: Key to Japanese species of Syzeuctus
(Males of S. brevicaudus sp. nov., S. laoticus and S. takaozanus unknown)
1. Females............................................................................................. 2
-. Males.............................................................................................. 13
2. Ovipositor shorter than hind tibia (Fig. 5 A); ovipositor sheath 0.85 × as long as hind tibia. Mesosoma and metasoma reddish-yellow except for blackish-brown median lobe of mesoscutum (Figs 5 A, B). Frons with a pair of convexities. Posterior transverse carina of propodeum absent.................................................... S. brevicaudus sp. nov.
-. Ovipositor longer than hind tibia (e.g. Fig. 1 A), ovipositor sheath at least 1.2 × as long as hind tibia. Mesosoma and metasoma largely black and/or yellow. Frons without a pair of conspicuous convexities. Posterior transverse carina of propodeum present (e.g. Fig. 15 F) or absent................................................................................ 3
3. Ovipositor sheath 1.25–1.4 × as long as hind tibia. Mesosoma and metasoma largely black (Figs 19 A, B). Large species: body length longer than 11 mm. Clouded area of fore wing weak and not defined as a restricted spot (Figs 19 A, B)............................................................................................ S. sambonis Uchida, 1928
-. Ovipositor sheath more than 1.9 × as long as hind tibia. Mesosoma and metasoma sometimes with large yellow spot(s)..... 4
4. Mesosoma, hind coxa, hind femur, and metasomal tergites entirely black (Figs 21 A, B). Ovipositor very long (Fig. 21 A); ovipositor sheath as long as or longer than body length and 3.35–3.7 × as long as hind tibia. Clouded area of fore wing weak and not defined as a restricted spot (Fig. 21 F).......................................... S. takaozanus Uchida, 1928
-. Mesosoma and metasomal tergites with yellow or red areas. Colouration of hind leg various. Ovipositor sheath slightly or distinctly shorter than body length........................................................................ 5
5. First to third hind tarsomeres each with clearly defined bicolour with black and yellow (Figs 10 A, F). First hind tarsomere yellow except for black base and apex. Second and third hind tarsomeres yellow basally and black apically. Hind fourth tarsomere yellow. Fifth hind tarsomere black. T I 1.5 × as long as maximum width. Face with a pair of distinct weak convexities above anterior tentorial pits. Hind femur reddish-yellow (Fig. 10 A). Posterior transverse carina present. Clouded area of fore wing weak and not defined as a restricted spot (Fig. 10 E)............................ S. flavofacialis Kang & Lee, 2020
-. Hind tarsus nearly almost unicolour or if bicolour, without clearly defined border (e.g. Figs 22 A, F). T I usually longer than 1.6 × as long as maximum width. Face with or without a pair of distinct convexities above anterior tentorial pits. Other character states various......................................................................................... 6
6. Clouded area of fore wing strong and defined as a restricted spot (Figs 3 B, 13 A, F). Metasomal tergites usually largely red or reddish-yellow (Figs 3 A, B, 13 A, B)...................................................................... 7
-. Clouded area of fore wing weak and not defined as a restricted spot (e.g. Fig. 6 B). Metasomal tergites usually without large reddish area.......................................................................................... 8
7. Apex of metasoma black (Figs 3 A, B). Small species: body length 7.0– 10.5 mm. T I 2.0–2.35 × as long as maximum width. Ovipositor sheath 2.5–2.8 × as long as hind tibia. Flagellum with 42–44 segments. Malar space 0.65–0.7 × as long as basal width of mandible................................................................. S. apicifer (Walker, 1874)
-. Apex of metasoma reddish-yellow (Figs 13 A, B). Large species: body length 11.7–15.0 mm. T I 2.3–2.6 × as long as maximum width. Ovipositor sheath 2.1–2.2 × as long as hind tibia. Flagellum with 46–49 segments. Malar space 0.55–0.6 × as long as basal width of mandible............................................................. S. maculatus Sheng, 2009
8. Body and legs largely yellow (Figs 6 A–D). Yellow areas of mesosoma and hind coxa distinctly larger than black areas respectively (Figs 6 A, B). Ovipositor sheath 2.35–2.55 × as long as hind tibia.................. S. coreanus Uchida, 1928
-. Body and legs largely black with smaller yellow areas. Yellow areas of mesosoma and hind coxa smaller than black areas respectively. Ovipositor sheath various in length............................................................. 9
9. Posterior transverse carina of propodeum present and complete (Fig. 15 F). Propodeum without a pair of antero-lateral yellow spots (Figs 15 B, F). T I 1.6–2.0 × as long as maximum width. Flagellum with 38–40 segments. Malar space 0.6–0.7 × as long as basal width of mandible. Ovipositor sheath 2.55–3.0 × as long as hind tibia. Hind femur black. Face with large black area (Fig. 15 C).............................................................................. S. nigrus sp. nov.
-. Posterior transverse carina of propodeum largely absent medially. Propodeum with a pair of antero-lateral yellow spots (Fig. 22 B). Other characteristics various......................................................................... 10
10. Ovipositor sheath distinctly longer than metasoma (Fig. 12 A) and 3.35–3.5 × as long as hind tibia. T I 2.0–2.6 × as long as maximum width. Face yellow except for a small median black area below antennal sockets, which black area not reaching ventral margin of face (Fig. 12 C)....................................................... S. laoticus Riedel, 2022
-. Ovipositor sheath shorter than 2.4 × as long as hind tibia. T I longer than 2.2 × as long as maximum width. Face various in colouration.......................................................................................... 11
11. Malar space 0.75–0.8 × as long as basal width of mandible. Metasomal tergites with red area on posterior parts (Figs 17 A, B). Face largely yellow (Figs 17 C, D). T I 2.55–2.95 × as long as maximum width. Mesopleuron sometimes without yellow markings except for subtegular ridge (Figs 17 F, G).......................................... S. rufiapicalis sp. nov.
-. Malar space 0.5–0.6 × as long as basal width of mandible. Metasomal tergites without red area (Figs 8 A, B, 22 A, B). Face black except for a pair of lateral yellow stripes (sometimes reduced) and a pair of yellow markings along eye margins (Figs 8 C, D, 22 C). T1 at most 2.4 × as long as maximum width. Mesopleuron with more than two yellow markings (including a marking on subtegular ridge) (Figs 8 F, 22 A, E)................................................................... 12
12. First to fourth hind tarsomeres ivory (Figs 8 A, H). Punctures on upper part of mesopleuron irregular and sparser than on lower part (Fig. 8 F). Posterior margin of T IV always yellow (Fig. 8 B)................................ S. flavitarsis sp. nov.
-. First to fourth hind tarsomeres at least partly blackish-brown (Figs 22 A, F). Punctures on upper part of mesopleuron as dense as on lower part (Fig. 22 E). Posterior margin of T IV usually black.............................. S. yamatonis sp. nov.
13. Spiracles of metasomal tergites enlarged and with circular felt-like area (Figs 2 P–S, 18 A, C, 23 D)................... 14
-. Spiracles of metasomal tergites not enlarged and with normal shape (Fig. 2 O).................................... 15
14. Body length 10.0– 12.2 mm. T I 2.7–2.8 × as long as maximum width. Enlarged spiracle of T I more than 0.2× as long as T I (Figs 2 P, Q). Posterior transverse carina of propodeum complete............................... S. rufiapicalis sp. nov.
-. Body length 8.5–10.0 mm. T I 2.4–2.65 × as long as maximum width. Enlarged spiracle of T I less than 0.2× as long as T I (Figs 2 R, S). Posterior transverse carina of propodeum largely absent medially......................... S. yamatonis sp. nov.
15. Flagellum with more than 50 segments. Body length longer than 11.0 mm........................................ 16
-. Flagellum with less than 46 segments. Body length shorter than 9.1 mm ......................................... 17
16. T I 2.0 × as long as maximum width. Malar space 0.35–0.4 × as long as basal width of mandible. Metasomal tergites and hind leg largely black to blackish-brown (Figs 20 A, B)........................................ S. sambonis Uchida, 1928
-. T I 2.75–3.05 × as long as maximum width. Malar space 0.6 × as long as basal width of mandible. Metasomal tergites and hind leg largely reddish-yellow (Figs 14 A, B)............................................... S. maculatus Sheng, 2009
17. First to third hind tarsomeres each clearly defined bicoloured with black and yellow (Fig. 11 A). First hind tarsomere yellow except for black base and apex. Second hind tarsomere yellow basally and black apically. Fourth hind tarsomere entirely yellow. Hind fifth tarsomere black. T I 2.05 × as long as maximum width. Malar space 0.65 × as long as basal width of mandible............................................................................. S. flavofacialis Kang & Lee, 2020
-. Hind tarsus nearly unicoloured or, if bicoloured, without clearly defined border. T I more than 2.1 × as long as maximum width. Malar space more than 0.75 × as long as basal width of mandible............................................... 18
18. Propodeum without a pair of antero-lateral yellow spots and with a posterior transverse carina (Fig. 16 B)... S. nigrus sp. nov.
-. Propodeum with a pair of antero-lateral yellow spots (e.g. Fig. 23 B). Propodeum with or without a posterior transverse carina.............................................................................................. 19
19. Propodeum with posterior transverse carina (Fig. 7 D). Body and legs largely yellow (Figs 7 A–D). Yellow areas of mesosoma and hind coxa distinctly larger than each black area respectively (Figs 7 A, B)................... S. coreanus Uchida, 1928
-. Propodeum without posterior transverse carina. Yellow areas of mesosoma and hind coxa as extended as or smaller than each black area respectively (Figs 4 A, B, 9 A, B)............................................................... 20
20. Metasomal tergites with a conspicuous large red area (sometimes reduced into base and apex of T II) (Figs 4 A, B). Fore wing clouded along apical margin (Figs 4 A, B). Hind tibia not darkened (Figs 4 A, B) or only slightly darkened near apex. Malar space 0.9–1.0 × as long as basal width of mandible....................................... S. apicifer (Walker, 1874)
-. Metasomal tergites without a conspicuous red area (Figs 4 A, B). Fore wing almost entirely hyaline (Figs 9 A, B). Hind tibia distinctly darkened apically (Fig. 9 A). Malar space 0.8 × as long as basal width of mandible.......... S. flavitarsis sp. nov.
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 36-38, DOI: 10.11646/zootaxa.5496.1.2, http://zenodo.org/record/13331013