Key to the species of Arocatus occurring in Taiwan 1 Dorsum almost uniformly red (except for the brownish membrane), without contrasting dark markings (Figs. 26–27)......................................................................................... A. nanus Breddin, 1909 - Body contrastingly bicolorous, red and black...............................................................2 2 Head with a large black median patch between eyes; pronotum black with red lateral margins and with a red median vitta, distinctly carinate along midline; body with long, semierect to erect pilosity (Figs. Figs. 28–31).......................................................................................... A. pseudosericans Gao, Kondorosy & Bu, 2013 - Head without dark interocular patch; pronotum black with red lateral margins but without red medial vitta, without trace of carina along midline; body with short, adpressed pilosity (Figs. 1–6).......................... A. elegantulus sp. nov.

Published as part of Tsai, Jing-Fu & Rédei, Dávid, 2017, The genus Arocatus in Taiwan (Hemiptera: Heteroptera: Lygaeidae), pp. 238-252 in Zootaxa 4299 (2) on page 250, DOI: 10.11646/zootaxa.4299.2.4, http://zenodo.org/record/835938