Trigonotoma Dejean 1828
Creators: name: Fedorenko, D. N.
Publisher: name: Zenodo
Year: 2024
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Coleoptera
Carabidae
Trigonotoma

description: Trigonotoma Dejean, 1828
Dejean, 1828: 182; Chaudoir, 1852: 71; Chaudoir, 1868: 158; Tschitschérine, 1900: 180; Andrewes, 1930: 352; Dubault et al., 2008a: 240; Roux et al., 2016: 22, 92; Zhu et al., 2020: 49.
Type species: Trigonotoma viridicollis (non Omaseus viridicollis Macleay, 1825): Dejean, 1828 = T. indica Brullé, 1834 (subsequent designation by Hope, 1838: 111).
DIAGNOSIS. A member of the ‘Trigonotomi’ group. Head more or less incrassate, with gula very wide, increasingly so toward base. Antennae geniculate, with scape long, from barely shorter to longer than antennomeres 2 to 4 combined; pedicel with seta; clypeus and labrum deeply sinuate at apical margins, usually leaving labral membrane widely exposed; labral setae evenly spaced; mentum short, with median tooth on a level with lateral lobes. Elytra without setigerous pores (except two species), stria 7 with three preapical setae. Mesoventrite mostly with a precoxal tooth on each side. Meso- and metatatarsomere 1 with at least anterior (outer) lateral setae. Terminal labial palpomere very widely triangular to (mostly) securiform in male. Median lobe of aedeagus with apex mostly lamellate, curved to the right, quadrate or trapezoidal.
Other characters as for the group: abdominal sternites transversely sulcate; mentum with deep labial pits; elytral umbilical seta series (USS) continuous. Leg setation: metacoxa bisetose (inner seta missing), metatrochanter asetose, metafemur with one seta (basal), metatibia externally and tarsomere 5 ventrally setose; metatarsomeres 1 and 2 with dorso-apical setae.
Aedeagus with median lobe slightly dorsoventrally flattened; right paramere short; internal sac dorsal or almost so; right paramere short. Female gonocoxite IX falcate, narrow, with indistinct nematiform seta and no ensiform setae.
REDESCRIPTION. Body mostly macropterous, BL 13– 32 mm dependent on species, shiny black to bright metallic. Eyes (Figs 1–6) medium-sized, convex, gena rather distinct, neck constriction shallow yet distinct. Mandibles moderate in length, with apex very pointed and strongly incurved. Frontal sulci mostly long.
Pronotum cordiform through subquadrate to nearly circular. Lateral bead rather thick, broadened and flattened toward base. Basal foveae moderately deep, rather flat at bottom, smooth to densely punctate or rugose; inner basal sulcus mostly deep, outer one more shallow, curved slightly outside and more or less distinctly extended into lateral groove inside lateral bead. Base without bead; apex laterally beaded.
Elytra oblong, with sides slightly rounded, humeri rather widely rounded yet distinct, and apices rounded combined. Basal ridge almost complete, inwardly reaching stria 1 or 2, or 3. Striae mostly deep and distinctly punctate or crenulate; parascutellar striole long; stria 1 adjoining parascutellar seta. Intervals mostly convex and more so toward apex. USS: 20–23 (for species from Vietnam).
Leg setation: profemur posterior face bisetose (basal seta missing); metatarsomeres 1 and 2 with a few or no posterolateral setae; ventral setae strong, spiniform, arranged in two rows, tarsomeres 2 and 3 with dorso-apical setae. Meso- and metatarsomeres 1–3 with anterolateral (outer) carina long and sharp to missing, with ventrolateral sulcus only traceable in the latter case.
Venter rather coarsely and densely punctate along sides, including propleura, meso- and metathorax, and abdominal sternites II–IV. Prosternal process not beaded, its posterior inclination wide and flat to sharply carinate. Mesoventrite with a distinct precoxal tooth on each side. Metepisternum mostly long (following macropterous condition) to short.
Secondary sexual characters. Protarsomeres 1–3 dilated and biserially squamose on ventral side in male. Labial palpomere 3 securiform in male, subtriangular, very slightly dilated toward apex, in female. Elytra barely shorter in female than in male (Tab. 1), with apices rounded or subtruncate (vs. angulate) combined. Mesotibia rugulose in apical half of anterolateral face, with a small latero-apical tooth just above longer movable apical spur, in male, smooth and without tooth in female.
Internal sac of aedeagus very different in shape, mostly either simple, more or less tubiform (Figs 59–76), or with additional, separate, dorsobasal bulb (Figs 77–80); this latter type of the internal sac is also characteristic of Pareuryaptus and Trigonaptus.
In species examined, female pregenital segments, genitalia and reproductive tract are similar to those of Lesticus (Figs 7–26, 31, 36–38), except chiefly for tergite VIII convex (vs. truncate or concave) at apical margin and spermatheca more robust, being shorter, wider and thence more differentiated. Spermathecal duct rather short and directly extended into receptacle, spermatheca proper; spermathecal gland short to very long, spermathecal gland duct rather short. Bursa copulatrix short, i.e., normal in length, to very elongated. No distinct sphincter at bases of spermathecal duct and common oviduct.
GEOGRAPHIC DISTRIBUTION. Throughout the Oriental region and the adjacent parts of southernmost Palearctic subregion within China to Japan.
Seven species have hitherto been reported or described from Vietnam: T. dohrnii Chaudoir, 1852; T. perraudieri Bates, 1889; T. nitidicollis Chaudoir, 1868; T. chrysites Bates, 1892 (as T. bhamoensis: Kuntzen, 1911); T. aurifera Tschitschérine, 1900; T. ledouxi Dubault et al., 2010; and T. stricta Dubault et al., 2011.
HABITATS AND HABITS. The adults of the species reviewed were collected in various habitats at lower altitudes, along forests trails and forest edges, as well as in fields. Many specimens were taken at light at night.
COMMENTS. The genus was revised recently [Roux et al., 2016], with key to the species provided and additional keys for particular regions such as India or Indochina, or Indonesia. In course of the revision, many new species were contributed to the genus, including those of the T. lewisii species group and of the T. nitidicollis species group [Dubault et al., 2010a, b]. Other results obtained included recognition of T. aurifera as a synonym of T. nitidicollis, and T. lewisii Bates, 1873, as a widespread polytypic species.
The groups discussed include altogether to ten species in Indochina. These all are very similar in appearance, except that the species of the the lewisii -group by comparison have the body slightly smaller, the meso- and metatarsi with (vs. without) longitudinal anterolateral carina (and sulcus above), and the metatarsi with a few or no posterolateral setae, respectively.
KEY TO SPECIES OF TRIGONOTOMA FROM VIETNAM
1(2) Pronotum densely punctate along base (Fig. 6). Body dorsum more or less unicoloured, deep green to nearly black, elytra rather shiny in male, dull in female. BL 19–22.5 mm. Elytra long, abouth three fourths longer than wide. Pronotum with base wide and posterolateral seta inserted much inside almost indistinct basal angle. — Indochina and southern China ..............6. T. dohrnii Chaudoir, 1852
2(1) Pronotum impunctate at least in middle of base (Figs 1–5).
3(4) Body dorsum uniform metallic green or bronzed. BL 21–28 mm. Tarsi neither laterally carinate nor sulcate. Mesoventrite without precoxal tooth. — Thailand to Vietnam. ........................................................7. T. perraudieri Bates, 1889
4(3) Dorsum contrastingly bicoloured, with forebody bright metallic green, golden green or cupreous green and elytra black to very deep violaceous. Mesoventrite in lateral view with a distinct precoxal tooth.
5(6) Pronotum impunctate, with basal foveae very shallow and sides subconvex in front of basal angles (Fig. 95). Metepisternum short, about as long at outer margin as wide at nterior margin. BL 21–24 mm. — Tam Dao, northern Vietnam. ....................... 5. T. ledouxi Dubault et al., 2010
6(5) Pronotal base punctate in basal foveae or except middle, if impunctate, then basal foveae deep. Metepisternum distincly longer than wide.
7(10) Body large, BL 23.7–27 mm. Tarsi without lateral carina or sulcus, metatarsomere 1 without posterolateral (inner) setae. Pronotal base impunctate between inner basal sulci. Aedeagus smooth ventrally. ...........The nitidicollis -group
8(9) Elytra black or with almost indistinct violaceous luster along reflexed lateral margin. Sides of pronotum mostly straight in front of obtuse and rounded basal angles (Fig. 2). Internal sac of aedeagus with no sclerites (Figs 62–64). — Indochina, mostly Laos and Vietnam. ......................... ........................................ 1. T. nitidicollis Chaudoir, 1868
9(8) Elytra with slight yet distinct violaceous luster, more so along reflexed lateral margin. Sides of pronotum mostly subsinuate in front of more distinct basal angles (Fig. 1). Internal sac of aedeagus with a large dorsal sclerite (Figs 59–61). — Throughout Indochina, no records in Vietnam. ................................ [2. T. aurifera Tschitschérine, 1900]
10(7) Body smaller, BL 16.7–22 mm. Tarsi mostly with a distinct lateral carina, metatarsomere 1 with 1–4 posterolateral setae. Pronotal base mostly distinctly punctate between inner basal sulci except medially. Aedeagus more or less densely striated on ventral side. ........... The lewisii -group
11(14) Apex of median lobe of aedeagus in right dorsolateral view quadrate (Figs 51–52).
12(13) Aedeagus in about middle third of ventral side densely striated throughout its width (Fig. 57); internal sac very transverse at base, with well-differentiated bulbs (Figs 65–72). BL 16.7–22 mm (19–22 mm in populations from Vietnam). — Myanmar to Vietnam; southern China (Yunnan). ....................................... 4. T. chrysites Bates, 1892
13(12) Aedeagus vaguely to rather distinctly striated along left lateral third to half of ventral side (Fig. 56); internal sac tubiform, slightly transverse at base, with bulbs not or barely differentiated (Figs 73–74). BL 17–18.5 mm [3. T. lewisii Bates, 1873]
14(11) Apex of median lobe of aedeagus in right dorsolateral view trapezoidal and longer. ............ [T. bhamoensis Bates, 1890]
description: Published as part of Fedorenko, D. N., 2024, Notes on Trigonotoma and Pareuryaptus (Coleoptera: Carabidae: Pterostichini) from Vietnam, pp. 43-71 in Russian Entomological Journal 33 (1) on pages 44-45, DOI: 10.15298/rusentj.33.1.05, http://zenodo.org/record/14162968