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.