Diochus Erichson 1839

Key to species of the genus Diochus of Thailand and Myanmar (Figs 1 −9) 1 Antennomeres shorter; antennomere 3 less elongate, nearly equal to antennomere 2................................. 2 - Antennomeres longer; antennomere 3 more elongate, distinctly longer than antennomere 2........................... 8 2 Antennomeres extremely short, antennomeres 6−10 transverse............................. D. umphangensis sp. nov. - Antennomeres longer, antennomeres 6−10 not transverse...................................................... 3 3 Posterior margin of male sternite VIII emarginate medially and on both sides...................................... 4 - Posterior margin of male sternite VIII emarginate only medially................................................ 5 4 Posterior margin of male sternite VIII with numerous short setae in medial emargination, and with fascicular setae in emarginations on both sides........................................... D. emarginatus Huang, Janák & Zhou, 2024 - Posterior margin of male sternite VIII without numerous setae in each emargination.................. D. crispus sp. nov. 5 Male sternite VIII distinctly projecting medially, well beyond lateral margin; basal margin of male sternite IX deeply emarginate; male aedeagus without several small irregular sclerites on upper middle.......................................... 6 - Male sternite VIII not distinctly projecting medially, only slightly beyond lateral margin; basal margin of male sternite IX straight; male aedeagus with several small irregular sclerites on upper middle................... D. balangensis sp. nov. 6 Pronotum less elongate. Male aedeagus with bilobate sclerites distally; parameres relatively shorter, not reaching apex of median lobe......................................................................... D. bilobatus sp. nov. - Pronotum distinctly more elongate. Male aedeagus without bilobate sclerites distally; parameres relatively longer, reaching beyond apex of median lobe............................................................................. 7 7 Head without elevation between eyes in males; basal furrow of male sternite VIII slightly emarginate in middle; male aedeagus with transverse sclerite distally and irregular sclerites in middle...................... D. antennatus (Motschulsky, 1858) - Head with a round elevation between eyes in males; basal furrow of male sternite VIII deeply emarginate in middle; male aedeagus with triangular sclerite distally and paired sclerites in middle.............. D. bisegmentatus Zhou & Zhou, 2016 8 Male sternite VIII with numerous setae on posterior margin.................................................... 9 - Male sternite VIII without numerous setae on posterior margin................................................ 10 9 Posterior margin of male sternite VIII shallowly emarginate, setae not so dense; aedeagus with paired horn-like sclerites............................................................................. D. conicollis (Motschulsky, 1858) - Posterior margin of male sternite VIII deeply emarginate, setae distinctly denser; aedeagus without paired horn-like sclerites..................................................................... D. setatus Huang, Janák & Zhou, 2024 10 Body larger, ca. 7.6 mm; posterior margin of male sternite VIII nearly straight; male sternite IX with width of apical margin about twice that of basal margin; male aedeagus long and slender, with parameres extremely short; tube of female spermatheca longer, with more than three bends........................................................ D. robustus sp. nov. - Body smaller, shorter than 6.0 mm; posterior margin of male sternite VIII not straight; width of apical margin of male sternite IX distinctly shorter than that of basal margin; male aedeagus shorter and wider, parameres longer; tube of female spermatheca shorter, with one or three bends......................................................................... 11 11 Eye large-sized, longitudinal diameter slightly longer than half the length of tempora........... D. myanmarensis sp. nov. - Eye small to medium sized, longitudinal diameter shorter than half the length of tempora........................... 12 12 Body smaller, ca. 4.0 mm, forebody ca. 2.4 mm, with lighter coloration; male sternite IX with largest point at basal 1/3; male aedeagus with a round sclerite at base........................................ D. punctipennis (Motschulsky, 1858) - Body larger, ca. 5.0 mm, forebody ca. 2.9 mm, with darker coloration; male sternite IX with largest point at basal half; male aedeagus without round sclerite......................................................................... 13 13 Male sternite VIII with posterior angles distinctly produced; male sternite IX more elongate; aedeagus with parameres relatively shorter; female spermatheca with tube bends relatively shorter............... D. caudapiscis Shuai, Nozaki & Tang, 2021 - Male sternite VIII with posterior angles not produced; male sternite IX less elongate; aedeagus with parameres relatively longer; female spermatheca with tube bends relatively longer............... D. guizhouensis Shuai, Nozaki & Tang, 2021