Two new Margarinotus Marseul, 1853 from Jiangxi, Guangxi, and Guangdong provinces (China), with an updated key to all Chinese species (Coleoptera, Histeridae, Histerinae, Histerini)

Two new species of <i>Margarinotus</i> Marseul, 1854 from southern China are described herein: Margarinotus (Grammostethus) mazuri<b>sp. nov</b>. and Margarinotus (Ptomister) deficiens<b>sp. nov</b>. Subgeneric placement of new taxa is only tentative, pending the phylogeny of the taxon. Almost all specimens were collected using flight interception or pitfall traps. The species Margarinotus (Grammostethus) arrosor (Bickhardt, 1920), <b>comb. nov</b>. and Margarinotus (Grammostethus) birmanus Lundgren, 1992 are herein re-described and figured. <i>Margarinotus arrosor</i> (Bickhardt, 1920) is transferred into subgenus <i>Grammostethus</i> Lewis, 1906 based on the structure of the aedeagus. The taxonomic status of the subgenus <i>Grammostethus</i> Lewis, 1906 is briefly discussed, and an updated key to all Chinese species is given. Lectotype and paralectotypes of <i>Hister gentilis</i> Lewis, 1891 (= Margarinotus (Grammostethus) birmanus)) are designated.