A review of Thysanarthria with description of seven new species and comments on its relationship to Chaetarthria (Hydrophilidae: Chaetarthriini)

Abstract

Abstract The Old World genus Thysanarthria Orchymont, 1926 is reviewed taxonomically and compared to the related genus Chaetarthria Stephens, 1835. Chaetarthria is considered to consist of three groups differing in the morphology of male genitalia and surrounding sclerites: (1) large Old World Chaetarthria which seems to stand apart of the remaining groups, and (2) European Chaetarthria plus (3) American Chaetarthria which both share the male sternite 8 with a long median projection with Thysanarthria. The reduced mesal part of male sternite 9 is shared by European Chaetarthria and Thysanarthria, supporting their close relationship proposed by previous molecular analyses. Sixteen species are recognized within Thysanarthria which differ in the details of the morphology of the aedeagus illustrated for all species. Seven species are described as new: T. bifida sp. nov. (Thailand), T. cardamona sp. nov. (India: Kerala), T. chui sp. nov. (Taiwan), T. persica sp. nov. (southern Iran), T. saurahana sp. nov. (Nepal), T. trifida (Laos), and T. wadicola sp. nov. (Oman). New records are provided for T. ceylonensis Hebauer, 2001 (new to India: Madhya Pradesh), T. championi (Knisch, 1924) (new to Afghanistan, India: Arunachal Pradesh, China: Yunnan, and Myanmar), T. madurensis Hebauer, 2001 (new to Nepal and India: Kerala), and T. siamensis Hebauer, 2001 (new to India: Uttarkhand, Nepal and Laos). Chaetarthriomorphus sulcatus Chiesa, 1967 is revealed as a junior synonym of Chaetarthria championi Knisch, 1924, and lectotypes are designated for both these taxa. An undescribed species of the American group of Chaetarthria is recorded from Saudi Arabia either as an accidental introduction or due to mislabeling; the species is illustrated but not described.