Key to species of Synapsis recorded from Vietnam The key is based on the specimens examined by us in NMPC and VNUF as well as on literature data (ARROW 1931, BALTHASAR 1963, KRÁL & REJSEK 2000, KRÁL 2002, HANBOONSONG & MASUMOTO 1999, OCHI & KON 2007, OCHI et al. 2008, ZÍDEK & POKORNÝ 2010). 1(6) Hypomeral cavities present (Figs 2 E–F). 2(3) Elytral interval 2 near base not swollen (Fig. 2A). .......................................... S. puluongensis sp. nov. 3(2) Elytral interval 2 near base swollen (Fig. 2B). 4(5) Metafemora in ventral view densely punctate, body length 17.5–24.0 mm. ...................................... ............................ S. horaki Zídek & Pokorný, 2010 5(4) Metafemora in ventral view not punctate, body length 27.0–29.0 mm (Fig. 2D). ............................... .................................................. S. yama Gillet, 1911 6(7) Hypomeral cavities absent. 7(10) Frons with minor horn or medial tubercle; mesepisternal cavities absent. 8(9) Genae not expanded, anterolateral angle of pronotum not dentate (Fig. 5A). ........................................ .............................................. S. simplex Sharp, 1875 9(8) Genae expanded; anterolateral angle of pronotum tridentate (Fig. 5B). ............ S. tridens Sharp, 1881 10(11) Frons without minor horn or only with medial tubercle; mesepisternal cavities present and covered with red setae (Figs 6 A–C, F). 11(12) Anterolateral angles of pronotum nearly rectangular (90°). Lateral angles of genae obtuse, rounded. Metafemora in ventral view sparsely punctate (Figs 6A, D). ................ S. ovalis Boucomont, 1920 12(11) Anterolateral angles of pronotum about 135°. Lateral angles of genae rather sharp, metafemora in ventral view densely punctate (Figs 6B, E). ............ ................................................. S. strnadi Král, 2002

Published as part of Bui, Van Bac & Bonkowski, Michael, 2018, Synapsis puluongensis sp. nov. and redescription of S. horaki (Coleoptera: Scarabaeidae), with a key to Vietnamese species, pp. 407-418 in Acta Entomologica Musei Nationalis Pragae (Acta. Ent. Mus. Natl. Pragae) (Acta. Ent. Mus. Natl. Pragae) 58 (2) on pages 416-417, DOI: 10.2478/aemnp-2018-0032, http://zenodo.org/record/4504894