Stenothemus Bourgeois, 1907

Ge, Shujuan, Yang, Xingke, Liu, Haoyu & Yang, Yuxia, 2021, Definitions of two species groups of Stenothemus Bourgeois (Coleoptera, Cantharidae), with descriptions of three new species from China, Zootaxa 5047 (2), pp. 139-152 : 150

Key to the species of Stenothemus Bourgeois

1. Female with abdominal tergite VIII curled ventrally on both sides ( Yang et al., 2014: figs 9‒10); male genitalia: ventral process of each paramere elongate and more or less expanded terminally, dorsal plate strongly narrowed apically, ventral process and dorsal plate bent ventrally together ( Yang et al. 2014: figs 21‒41).......................... S. harmandi species-group

- Female with abdominal tergite VIII normal, not as above; male genitalia: ventral process and dorsal plate of each paramere normal, not as above or hardly bent ventrally.............................................................. .. 2

2. Body stout, less than 4.0 × as long as wide; head width across eyes nearly as long as or narrower than anterior margin of pronotum in males; male genitalia: dorsal plates simple and not layered............................................ .. 3

- Body slender or stout, if stout, dorsal plates layered in the middle; if slender, the body more than 4.0 × as long as wide, head width across eyes wider than anterior margin of pronotum in males................................................................................all other species (including dozens of species will be treated in a forthcoming work)

3. Scutellum pitch black; male genitalia: ventral processes of parameres slender and bent inwards at apical part in ventral view, not thickened at apex, laterophyses tilting ventrally at an angle of more than 45° with dorsal plates, compressed and longitudinally divided at apical part ( S. laterophysus species-group)......................................................... 4

- Scutellum yellow; male genitalia: ventral processes of parameres stouter and diverging apically in ventral view, thickened at apex, laterophyses relatively parallel to dorsal plates, expanded apically, divided at apices ( S. notaticollis species-group)... 5

4. Head with a triangular marking on vertex, legs mostly yellow, black at apical part of femora and basal part of tibiae ( Fig. 1A ); male genitalia: ventral processes of parameres nearly as long as dorsal plates, laterophyses stout at basal part and abruptly narrowed apically in ventral view ( Švihla 2004: fig. 146).................................. S. laterophysus Švihla, 2004

- Head with a longitudinal marking on vertex, legs mostly black, yellow at coxae, trochanters and basal part of femora ( Fig. 2A ); male genitalia: ventral processes of parameres longer than dorsal plates, laterophyse slender and evenly narrowed in ventral view ( Figs 3A‒C )..................................................................... S. nigritibius sp. nov.

5. Head and elytra pitch black, pronotum mostly pitch black, yellowish brown or reddish brown at anterior angles.......... 6

- Head and elytra pale-yellow or brown, pronotum pale-yellow with black brown markings on disc...................... 7

6. Male antennae shorter and slightly over elytral half-length, antennomeres II slightly longer than wide at apices, III more longer than II ( Fig. 2C ); male genitalia: strongly swollen laterally at basal part in ventral view, dorsal plates longer than ventral processes of parameres, with outer apical angles acute in dorsal view ( Figs 3G‒I ).................... S. acutiapicis sp. nov.

- Male antennae longer and reaching apical one-third length of elytra, antennomeres II obviously longer than wide at apices, III less longer than II ( Fig. 2B ); male genitalia: moderately swollen laterally at basal part in ventral view, dorsal plates nearly as long as ventral processes of parameres, with outer apical angels subrounded in dorsal view ( Figs. 3D‒F ).................................................................................................. S. parameratus sp. nov.

7. Male genitalia: dorsal plates evenly narrowed apically, ventral processes with apices directing ventrally in ventral view ( Wittmer, 1974: fig. 1)............................................................. S. notaticollis ( Gorham, 1895)

- Male genitalia: dorsal plates abruptly narrowed in the middle, ventral processes with apices directing laterally in ventral view ................................................................................................... 8

8. Head and elytra uniformly pale-yellow, legs mostly yellow, tibiae and tarsi dark brown ( Švihla, 2011: fig. 24); male genitalia: dorsal plates narrower and acute at apices, with nearly straight inner margins ( Švihla, 2011: figs 105‒107).................................................................................................. S. tamil Švihla, 2011

- Head and elytra mostly black brown, with reddish brown marking on vertex, leg black brown, coxae, trochanters and basal part of femora yellowish brown; male genitalia: dorsal plates wider, subrounded at apices and widely emarginate at inner margins ( Wittmer, 1974: fig. 3; Švihla, 2011: figs 108‒109)..................................... S. bourgeoisi Wittmer, 1974

Figures

FIGURE 1. Habitus of Stenothemus, dorsal view (A‒C, holotype, D, specimen identified by Dr.W. Wittmer): A. S. laterophysus Švihla, 2004; B. S. bourgeoisi Wittmer, 1974; C‒D. S. notaticollis (Gorham, 1895).

FIGURE 2. Habitus of Stenothemus, dorsal view: A. S. nigritibius sp. nov.; B. S. parameratus sp. nov.; C. S. acutiapicis sp. nov. Scale bars: 2.0 mm.

FIGURE 3. Male genitalia of Stenothemus (A, D, G. ventral view; B, E, H. dorsal view; C, F, I. lateral view): A‒C. S. nigritibius sp. nov.; D‒F. S. parameratus sp. nov.; G‒I. S. acutiapicis sp. nov. Scale bars: 1.0 mm.