Homotropus Forster 1869
Creators: name: Morishita, Shunsuke
name: Watanabe, Kyohei
Publisher: name: Zenodo
Year: 2025
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Hymenoptera
Ichneumonidae
Homotropus

description: Genus Homotropus Förster, 1869
Homotropus Förster, 1869: 162.
Type species: Bassus elegans Gravenhorst, 1829. Designated by Viereck (1912).
Homoporus Thomson, 1890: 1488. Lapsus for Homotropus.
Homocidus Morley, 1911: 87. New name for Homoporus.
Diagnosis. According to Klopfstein (2014b), this genus can be distinguished from other genera by the following combination of character states. Face coriaceous and matt; without vertical impressions; entirely black or black with yellow central marking in female (Figs 2 B, 3 B, 4 B, 5 B, 6 B, 7 B, 9 B, 10 B, 11 B, 12 B, 13 B); entirely yellow or black with yellow inner orbits and yellow central marking in male (Figs 2 E, 3 E, 4 D, 6 F, 8 B, 10 E, 11 F, 12 F, 13 D). Clypeus usually with thin apical margin; impressed along apical margin; resulting in central area being convex. Antenna with apical flagellomeres usually longer than wide. Tyloids always present in male; linear and narrow and without long setae in most species (exceptions: H. tauriscorium and H. venustus). Mesoscutum without notaulus; variously sculptured, ranging from entirely smooth and shining, with or without punctures, to being strongly coriaceous and matt; yellow shoulder markings present or absent; inner corners of markings (if present) sometimes extended into two parallel lines on mesoscutum. Scutellum only carinate basally. Mesopleuron sometimes entirely smooth and shining; often punctate and/or coriaceous at least on lower half; epicnemial carina complete ventrally. Propodeum sometimes with full set of carinae enclosing basal, petiolar, and lateral areas; carinae usually partly or fully reduced; spiracle inconspicuous. Areolet present or absent, if present, vein 3rs-m often interrupted or unpigmented. Hind wing with 2–4 basal hamuli. Hind tibia with various colouration, i.e., orange, yellow, or white with dark apex and subbasal spot, very rarely (H. venustus) even black-white-black banded. Female metasoma usually evenly tapered to apex (Figs 3 D, 6 D); sometimes strongly compressed posterior to third segment (Fig. 12 D); posterior margins never concave; without transverse impressions. T I usually without latero-median carina, but if carina present, its two carinae converge over basal half, parallel, and widely separated on apical half (Fig. 1 B). T II with spiracle above lateral fold. T III with spiracle usually above (but rarely below) or behind lateral fold. Metasoma black (Fig. 3 D); sometimes with yellow markings, or marked with orange (Figs 6 D, G, 11 G, 12 D). Ovipositor sheaths 0.3 × as long as hind tibia; either parallel-sided and fully enclosing ovipositor or tapered and diagonally truncate; with inconspicuous setae ventrally and apically. T VIII and T IX of male present as separate sclerites; hypopygium about 2.0 × wider than long, emarginated apically and forming two lobes; outer corners of lobes rounded.
Distribution. Holarctic, Neotropical, and Oriental regions (Yu et al., 2016).
Key to the Japanese species of the genus Homotropus
(males of H. kuroashii and H. japonicum are unknown)
1. Face black with pair of yellow markings along each inner orbit (Fig. 8 B). Propodeum with petiolar area surrounded by carinae (Fig. 1 C).......................................................... Homotropus klopfsteinae Johansson, 2020
-. Face without pair of yellow markings along each inner orbit (Figs 2 B, E, 3 B, E, 4 B, D, 5 B, 6 B, F, 7 B, 9 B, 10 B, E, 11 B, F, 12 B, F, 13 B, D). Character states of propodeum various.................................................... 2
3. Female............................................................................................. 3
-. Male.............................................................................................. 14
3. Fore and mid coxae mainly yellow to orange (Figs 2 A, 10 A). Metasoma entirely black (e.g., Fig. 3 D)................. 4
-. Coloration of fore and mid coxae mainly black, at most with yellow apices (Figs 3 A, 4 A, 5 A, 6 A, 7 A, 9 A, 13 A). If fore and mid coxae mainly yellow to orange, T II to T IV with orange markings (e.g., Fig. 12 D)............................. 5
4. Face entirely black or black with small median marking (Fig. 2 B). Scutellum black with yellow apical marking (Fig. 2 C)......................................................................... Homotropus areolaris (Uchida, 1957)
-. Face with yellow marking confluent with yellow clypeus (Fig. 10 B). Scutellum yellow with black basomedian marking which sometimes reduced (Fig. 10 C)............................................. Homotropus megaspis Thomson, 1890
5. Scutellum entirely black (e.g., Fig. 12 C)................................................................... 6
-. Scutellum black with yellow marking (e.g., Figs 2C, 10 C, 11 C)............................................... 10
6. Metasoma compressed apically (Fig. 12 D). T II to T IV entirely orange (Fig. 12 D)................................................................................................... Homotropus signatus (Gravenhorst, 1829)
-. Metasoma dorsoventrally depressed (e.g., Figs 3 D, 6 D). Coloration of T II to T IV various.......................... 7
7. T II to T IV with brown markings (Fig. 6 D). Punctures of mesopleuron usually absent, at most very sparsely punctate anteriorly and ventrally (Fig. 6 C).................................................. Homotropus infuscatus (Uchida, 1957)
-. Metasoma entirely black (e.g., Fig 3 D). Mesopleuron densely punctate (Figs 3 C, 5 C, 9 C).......................... 8
8. Yellow shoulder markings of mesoscutum absent (Fig. 3 A). Areolet usually absent (Fig. 3 A). Latero-median carina present basal 0.7–0.9 of T I (e.g., Fig. 1 B). T II less than 0.65 × as long as maximum width.................................................................................................... Homotropus crassicornis Thomson, 1890
-. Yellow shoulder markings of mesoscutum present (Figs 5 A, 9 A). Areolet present (e.g., Fig. 13 C). Latero-median carina usually indistinct, at most present on less than basal 0.4 of T I (e.g., Fig. 1 A). T II more than 0.8 × as long as maximum width ................................................................................................... 9
9. Mesopleuron coriaceous and matt over entire surface; densely punctate except for small smooth area around speculum (Fig. 5 C). Mesoscutum coriaceous and matt between punctures....................... Homotropus formosus Klopfstein, 2014
-. Mesopleuron smooth and polished except for coriaceous area on lower half of mesopleuron; densely punctate except for on and below speculum (Fig. 9 C). Mesoscutum weakly coriaceous and polished between punctures........................................................................................... Homotropus kuroashii (Uchida, 1957) (part)
10. Latero-median carina present basal 0.7–0.9 of T I (Fig. 1 B). Propodeum coarsely rugulose (Fig. 13 E)..................................................................................... Homotropus sundevalli (Holmgren, 1858)
-. Latero-median carina usually indistinct, at most present on less than basal 0.4 of T I (e.g., Fig. 1 A). Propodeum at most finely rugulose (e.g., Fig. 11 D).............................................................................. 11
11. T II to T IV entirely or largely orange (e.g., Fig. 12 D)....................................................... 12
-. T II to T IV entirely black (e.g., Fig. 3 D)................................................................. 13
12. Mesopleuron densely punctate except for on and below speculum (e.g., Fig. 9 C). Scutellum black with yellow apical marking (e.g., Fig. 2 C). Propodeum sometimes with some rugae centrally............... Homotropus elegans (Gravenhorst, 1829)
-. Punctures on mesopleuron usually absent; at most with very sparse punctures anteriorly and ventrally (e.g., Fig. 6 C). Scutellum black with largely yellow marking (Fig. 11 C). Propodeum without rugae......... Homotropus pallipes (Gravenhorst, 1829)
13. Hind tibia black with subbasal white marking (Fig. 7 C). Fore wing length 6.5–8.5 mm. T I 0.9–1.1 × as long as maximum width. T II 0.6–0.7 × as long as maximum width. T II 0.9–0.95 × as long as T I........... Homotropus japonicum sp. nov.
-. Hind tibia white; darkened basally and apically (Fig. 9 D). Fore wing length 4.5–6.0 mm. T I 1.05–1.25 × as long as maximum width. T II 0.85–1.1 × as long as maximum width. T II 1.0–1.05 × as long as T I...... Homotropus kuroashii (Uchida, 1957)
14. T III entirely or largely orange (e.g., Fig. 9 D).............................................................. 15
-. T III entirely or largely black (e.g., Figs 6 G, 11 G).......................................................... 16
15. Malar space entirely yellow (Fig. 4 D). Scutellum black with yellow apical marking (e.g., Fig. 2 C). Mesopleuron densely punctate except for on and below speculum (e.g., Fig. 9 C).................... Homotropus elegans (Gravenhorst, 1829)
-. Malar space entirely black (Fig. 12 F). Scutellum entirely black (e.g., Fig. 12 C). Punctures on mesopleuron usually absent, at most with very sparse punctures anteriorly and ventrally (e.g., Fig. 6 C)......... Homotropus signatus (Gravenhorst, 1829)
16. Scutellum entirely black (e.g., Fig. 12 C).................................................................. 17
-. Scutellum black with yellow marking (e.g. Figs 2C, 10 C, 11 C)............................................... 19
17. Clypeus bicolour (yellow with basal brown marking) (Fig. 6 F). Metasoma black with yellow to brown marking (Fig. 6 G)....................................................................... Homotropus infuscatus (Uchida, 1957)
-. Clypeus unicolour (entirely yellow) (Fig. 2 E, 3 F, 10 E, 11F) Metasoma entirely black (e.g., Fig. 3 D)................. 18
18. Areolet absent (Fig. 3 A). Latero-median carina present basal 0.7–0.9 of T I (e.g., Fig. 1 B). Antenna with 20 flagellomeres..................................................................... Homotropus crassicornis Thomson, 1890
-. Areolet present (e.g., Fig. 13 C). Latero-median carina of T I usually indistinct, at most present on less than basal 0.4 of T I (Fig. 1 A). Antenna with 23 flagellomeres....................................... Homotropus formosus Klopfstein, 2014
19. Latero-median carina present basal 0.7–0.9 of T I (Fig. 1 B). Hind coxa entirely black (Fig. 13 C). Propodeum coarsely rugulose (Fig. 13 E)........................................................... Homotropus sundevalli (Holmgren, 1858)
-. Latero-median carina of T I usually indistinct, at most present on less than basal 0.4 of T I (e.g., Fig. 1 A). Hind coxa black or orange with yellow apex (Figs 2 D, 10 D, 11 E). Propodeum at most finely rugulose (e.g., Fig 11 D).................. 20
20. T II to T IV with irregular orange markings (Fig. 11 G). Mesopleuron punctures usually absent, at most with very sparse punctures anteriorly and ventrally (e.g., Fig. 6 C)............................ Homotropus pallipes (Gravenhorst, 1829)
-. T II to T IV entirely black (e.g., Fig. 3 D). Mesopleuron densely punctate except for on and below speculum (e.g., Fig. 9 C).. .................................................................................................. 21
21. Scutellum black with yellow apical marking (e.g., Fig. 2 C)....................... Homotropus areolaris (Uchida, 1957)
-. Scutellum yellow with black basomedian marking which sometimes reduced (e.g., Fig. 10 C)............................................................................................... Homotropus megaspis Thomson, 1890
description: Published as part of Morishita, Shunsuke & Watanabe, Kyohei, 2025, Review of the genera Homotropus Förster and Syrphoctonus Förster (Hymenoptera, Ichneumonidae, Diplazontinae) from Japan, pp. 49-76 in Zootaxa 5588 (1) on pages 51-52, DOI: 10.11646/zootaxa.5588.1.2, http://zenodo.org/record/14896032