The genus Xylocoris found from plant debris in Thailand, with description of a new species of the subgenus Arrostelus (Hemiptera: Heteroptera: Anthocoridae) Author Yamada, Kazutaka Tokushima Prefectural Museum, Bunka-no-Mori Park, Mukôterayama, Hachiman-chô, Tokushima, 770 - 8070 Japan; e-mail: yamada. kaz @ gmail. com Author Yasunaga, Tomohide Research Associate, American Museum of Natural History, New York 10024; e-mail: tyasunaga @ amnh. org Author Artchawakom, Taksin Sakaerat Environmental Research Station (SERS), Sakaerat Biosphere Reserve, Thailand Institute of Scientific & Technological Research (TISTR), Ministry of Science and Technology, 1 Moo 9, A. Udom Sab, Wang Nam Khieo, Nakhon Ratchasima, 30370 Thailand; e-mail: sakaerat @ tistr. or. th Author Sers text Acta Entomologica Musei Nationalis Pragae 2013 2013-11-15 53 2 493 504 journal article 10.5281/zenodo.5740713 0374-1036 5740713 5FF3E23F-454D-41BF-9696-818A8F2B4B6E Key to species of Xylocoris occurring in the Oriental Region The present key is modified from those provided by YAMADA et al. (2006: 532) . 1. Male tibial teeth always absent; ostiolar peritreme smooth, lacking canaliculi; ectospermalege absent. Wing dimorphism present. (Subgen. Arrostelus ) .................................. 2 – Male tibial teeth always present on fore and middle legs; ostiolar peritreme densely covered with canaliculi; ectospermalege always present on right side of anterodorsal area of abdomen. Wing dimorphism absent. (Subgen. Proxylocoris ) ................................... 3 2. Clavus, endocorium, and embolium yellowish-brown; all femora uniformly pale yellow. .................................................................................. X. ( A. ) flavipes (Reuter, 1875) – Clavus widely darkened along inner margin and claval commissure; endocorium narrowly darkened along corium-membrane boundary; embolium widely darkened along outer margin; all femora uniformly black to blackish-brown. .................................................... .................................................................... X. ( A. ) ampoli Yamada & Yasunaga sp. nov. 3. Corium darkened along corium-membrane boundary, and with dark sub-triangular spot at apico-mesial corium; ectospermalege much smaller, extending posteriorly. ................ ....................................................................... X. ( P. ) cerealis Yamada & Yasunaga, 2006 – Corium narrowly darkened along corium-membrane boundary, without dark subtriangular spot; ectospermalege large, broadened anteriorly. ......................................................... 4 4. Body larger (about 3.0 mm long); apex of paramere extending well beyond the tip of laterally produced left side of pygophore; ectospermalege vague, conical. ...................... ........................................................................................... X. ( P. ) clarus (Distant, 1910) – Body smaller (about 2.3 mm long); apex of paramere extending near the tip of laterally produced left side of pygophore; ectospermalege with a complexly folded thin duct on right lateral margin. ............................ X. ( P. ) hyalinipennis Yamada & Yasunaga, 2006