A review of Thysanarthria with description of seven new species and comments on its relationship to Chaetarthria (Hydrophilidae: Chaetarthriini) Author Fikáček, Martin Department of Entomology, National Museum, Cirkusová 1740, CZ- 19100 Praha 9 – Horní Počernice, Czech Republic & Department of Zoology, Faculty of Science, Charles University, Viničná 7, CZ- 12844 Praha 2, Czech Republic mfikacek@gmail.com Author Liu, Hsing-Che Department of Environmental Engineering and Management, Chaoyang University of Technology, No. 168, Jifeng E. Rd., Taichung City 413, Taiwan td965771@gmail.com text Acta Entomologica Musei Nationalis Pragae 2019 2019-06-20 59 1 229 252 journal article 8143 10.2478/aemnp-2019-0020 a03ecce2-b526-4f94-aa65-620016956099 1804-6487 4488918 9F309FCC-A2ED-47B9-BC37-D0C4A3B482E5 Thysanarthria chui sp. nov. ( Figs 8 A–E, 11 ) Type material. HOLOTYPE : ♂ ( NMNS ), TAIWAN : Kaohsiung , Shanpin [= Shan Ping Forest Ecological Garden ], at light , 22.-23.iv.2003 , lgt. C. S. Lin . PARATYPES : 20 spec. ( NMNS , TARI , NMPC , NHMW , BMNH ): TAIWAN : Taichung City ,Wufeng district,Zhongkeng Industry Road, 4.3 km SEE of Chaoyang Univ. of Technology, 24.054983N 120.755433E , 180 m , 25.iv.–14.v.2019 , H.-C. Liu lgt., on sandy banks of of small slowly running lowland stream. Additional material examined. TAIWAN : LANYU ISLAND: 1 ♀ ( TARI ): Lanyu, 27.vii.2015 , lgt.Y.-T. Wang. The specimen corresponds with the holotype in all extrernal characters and we are hence assigning it to T.chui . However, since male genitalia are needed for reliable identification, I am not including this specimen among the types. Description. Body length 1.3–1.6 mm ( holotype 1.6 mm ), maximum body width 0.9–1.0 mm ( holotype 1.0 mm). Head and labrum black; pronotum brown in the middle, becoming weakly paler towards margins; elytra uniformly dark brown; legs brown. Head without microsculpture on interstices; punctation sparse, each puncture bearing pointed seta. Eyes separated by 3.8× the width of one eye in dorsal view. Pronotum with sparse setiferous punctation similar to that on head; interstices without microsculpture. Elytra with 10 striae sharply impressed except anteromedially (near scutellar shield) where neither striae nor serial punctures are visible; intervals weakly convex at midlength and near apex; interval punctation sparse, setiferous; interstices without microsculpture. Aedeagus ( Figs 8 A–E) 0.5 mm long. Phallobase indistinctly wider at base of parameres, only very weakly constricted more basally, arcuate in lateral view. Parameres wide basally, gradually narrowing towards apex, outer face subrectangular in basal two thirds, apex projecting into narrow rounded lobe. Median lobe narrow apically, rounded and membranous at apex, reaching to the level of parameral apices, pair of subapical projections missing; gonopore transversely oval, situated in apical fourth. Differential diagnosis. Thysanarthria chui externally differs from part of the remaining species in the total absence of dorsal microsculpture and rather dark (brown rather than yellowish) coloration. In the genital morphology it resembles T. championi , T. bifida , and T. trifida in the form of the parameres; T. bifida and T. trifida differ in the presence of a pair of subapically situated membranous lobes (absent in T. chui and T. championi ). For differences from T. championi see under that species. Etymology. The first author dedicates this new species to Isaac Chu as thanks for introducing him to Taiwan and its culture. The first known specimen of the new species was moreover collected in Mr. Chu’s home city of Kaohsiung . Biology. Paratypes were collected on a sandy bank of a slowly running lowland stream; they were actively crawling on the wet sand out of the water during the day ( Figs 11 F–G). The holotype was collected at light. Distribution. The species is known from the lowland localities in western and southern Taiwan . The occurrence on Lanyu (= Orchid Island) needs to be confirmed by examination of a male specimen.