Coelostoma

Liu, Hsing-Che, Hu, Fang-Shuo & Fikáček, Martin, 2020, Review of the genus Coelostoma of Taiwan with description of a new species (Coleoptera: Hydrophilidae), Acta Entomologica Musei Nationalis Pragae 60 (1), pp. 155-162 : 161

Key to Taiwanese species of Coelostoma

1 Mesofemora densely pubescent except on apex ( Fig. 2E ). Labrum yellowish ( Fig. 2G ). (subgenus Lachnocoelostoma ). ..................................................................... 2

– Mesofemora not densely pubescent, at most with sparse short setae. Labrum black with yellow margins ( Fig. 2H ). ................................................................................... 4

2 Apical part of median lobe trilobate ( Fig. 2C ). .............. ................................... C. phallicum Orchymont, 1940

– Apical part of median lobe simple. .............................. 3

3 Parameres widened apically, apex of median lobe rounded ( Fig. 2D ). ........................ C. wui Orchymont, 1940

– Parameres not distinctly widened apically, apex of median lobe subtriangular (Fig. 1C). ................................... .................................................. C. taiwanense sp. nov.

4 Abdominal ventrite V feebly emarginate posteromesally, bearing stout setae mesally. Gonopore apical (subgenus Holocoelostoma ). ...................................................... 5

– Posterior margin of abdominal ventrite V entire, not emarginate in the middle, without stout setae. Gonopore subapical (subgenus Coelostoma ). ....................... 6

5 Median lobe of aedeagus almost parallel-sided with broadly rounded apex ( Fig. 2E ). ...................................... ..................................... C. bhutanicum Jayaswal, 1972

– Median lobe of aedeagus wide in basal half, narrow in apical half ( Fig. 2F ). ............ C. stultum ( Walker, 1858)

6 Parameres rounded apically, with tuħ of setae at apex. Median lobe gradually narrowing towards apex ( Fig. 2B ). .................................... C. vitalisi Orchymont, 1923

– Parameres pointed apically, without tuħ of setae at apex. Median lobe wide basally and abruptly narrowed at midlength ( Fig. 2A ). ..................................................... ................................ C. fallaciosum Orchymont, 1936

Figures

Fig. 2. male genitalia and front view of the head of Taiwanese Coelostoma species.A–F – genitals in dorsal view:A – C. fallaciosum Orchymont, 1936; B – C. vitalisi Orchymont, 1923; C – C. phallicum Orchymont, 1940; D – C. wui Orchymont, 1940; E – C. bhutanicum Jayaswal, 1972; F – C. stultum (Walker, 1858), specimen from Japan: Iriomote Island; G–H – front view of head with labrum: G – C. taiwanense sp. nov., paratype; H – C. fallaciosum.