Hexachaetus Chaudoir, 1871

Tian, Mingyi & Deuve, Thierry, 2016, Re-definition and review of the Oriental genus Hexachaetus Chaudoir, 1871 (Coleoptera: Carabidae: Orthogoniini), Zootaxa 4169 (3), pp. 540-554 : 541-542

Genus Hexachaetus Chaudoir, 1871

Chaudoir, 1871: 98; Andrewes, 1930: 179; Csiki, 1932: 1592; Jedlička, 1963: 523 Type species: Orthogonius lateralis Guérin, 1843

Diagnosis. Combination of following characteristics are identical for members of the genus Hexachaetus : middle to large sized, glabrous and smooth, impunctate, yellowish to brown in most species; eyes very large and prominent, labrum emarginated, arcuate, or straight at front, clypeus bisetose in most species (but 6-setose in H. vietnamensis and H. prodigus ); ligula distinctly dilated, 4- or 6-setose at apex in most of species (but 12-setose in H. vietnamensis n. sp.); palps normal for most species (but stout in H. vietnamensis ); mentum edentate, bisetose at base, submentum bisetose, palpiger asetose; antennae moderate or long, extending over shoulders or at middle of elytra; pronotum strongly transverse in most species (moderately transverse or quadrate in others), fore angle always broadly rounded, hind angles obtuse, broadly round off in most species, or somewhat angular in others; elytral elongate-ovate, with base completely bordered, parallel-sided, odd and even intervals subequal in width; striae deep or shallow, punctate-striate, elytra with or without well-shaped black marking, apex of elytra obliquely truncated, making outer angles distinct or not, inner angle sharply pointed and denticulate in most species; interval 3 with only anterior and posterior setiferous pores, the median one always wanted, interval 7 simple; legs moderate or rather slender, middle and hind coxae asetose in median portion, femora quite slender, hind femora with two setae posteriorly; fore tibia slender, enlarged at apex, outer angles obtuse, rectangular or not, outer margin more or less serrated, middle tibiae inflated or not in male; hind tibiae slender, hardly dilated at apex, with apical tibial spurs long and sharp in most species (stout and broadly sword-like in H. vietnamensis n. sp. and H. mulan n. sp.), tarsomere 4 deeply emarginated and bilobed; all tarsal claws pectinate; prosternal process unbordered at apex; abdominal ventrite VII deeply emarginated medially at apical margin in male; male genitalia short and stout, various shaped, the apical lamella very short and broad, parameres normal for orthogoniines.

Sexual dimorphism. In male, protarsomeres 1-3 bearing two rows of spongy setae ventrally, middle tibiae distinctly inflated in most species, the abdominal ventrite VII narrowly but deeply emarginated at apical margin, and aedeagus are more or less exposed.

Generic range. Oriental Region (still not recorded from India, Sri Lanka, Nepal, Cambodia and the Philippines) ( Fig. 20 ).

Biological characteristics. There is still unknown the life cycle and biological characters of Hexachaetus species. Probably like Orthogonius species, they are also termitophilous.

Members of Hexachaetus can be provisionally divided into six species groups, viz. lateralis species group, laevissimus species group, vietnamensis species group, prodigus species group, mulan species group and angulatus species group. The former five species groups are dealt with in the present paper. The angulatus group is composed of more than ten species for which still remains some confusion and will be treated in a later paper.

Figures

FIGURE 20. Distribution of Hexachaetus species (square: angulatus species group; round: lateralis species group; star: laevissimus species group; heart: vietnamensis species group; triangle: mulan species group; a. H. lateralis lateralis; b. H. lateralis maindroni; c. H. maculatus; d. H. kirschenhoferi n. sp.; e. H. brunki n. sp.; f. H. laevissimus; g. H. vietnamensis n. sp.; h. H. prodigus; i. H. mulan n. sp.)