Two new species, Oia probosciella, new species and Nasoonaria annam, new species, are described from northern and southern Vietnam, respectively. Enguterothrix simpulum (Tanasevitch, 2014) and Nematogmus digitatus Fei & Zhu, 1994, are recorded from Vietnam for the first time. Considering the above novelties, the linyphiid spider fauna of Vietnam presently comprises 27 species.

Two new species of the genus Acutigebia (Decapoda: Gebiidae: Upogebiidae) collected from Xisha (Spratly) Islands are described. Acutigebia serrifera, new species, most closely resembles Acutigebia simsoni (Thomson, 1893), but differs markedly in the propodus of pereopod 1 with lower teeth. Acutigebia laticauda, new species, most closely resembles Acutigebia trypeta (Sakai, 1970), but differs markedly in the proportionally wider telson. This is the fi rst record of the genus Acutigebia from the South China Sea. An updated key to the species of Acutigebia is provided.

Two new species of the thread-legged bug genus Ademula McAtee & Malloch, 1926 (Hemiptera: Reduviidae: Emesinae: Emesini, formerly Ploiariolini) from China, A. callipennis, new species, and A. corniculata, new species, are described and illustrated in the present paper. COI barcodes of these two new species and an updated key to the Oriental species of Ademula are provided. The distribution of Ademula in East and Southeast Asia is briefly discussed.

Barbodes sellifer, new species, is described from Singapore, the southern Malay Peninsula and Riau (Sumatra). It is distinguished by having, among others, a large triangular to rectangular blotch between the dorsal fin and the midlateral row of scales (+1). Barbodes zakariaismaili, new species, is described from the Jelai watershed of the Pahang drainage. It is distinguished, among others, by having an elongated blotch on the anterior third of scale rows 0 and +1, and a narrow, faint bar between dorsal-fin origin and scale row +1. The existence of the supposed B. binotatus cryptic species is discussed; it does not satisfy any of the criteria under different concepts and this terminology should not be used. Among others, it is made of diagnosable units, and the morphological disparity among the supposed ‘cryptic’ taxa is not substantially lower than among non-‘cryptic’ relatives. It is simply a taxonomically difficult group.

Two new species of blackwater catfishes are described from Pulau Natuna Besar of the Natuna Archipelago, Indonesia. Silurichthys insulanus (Siluridae), new species, differs from all congeners in having a combination of characters: eye diameter 8% HL; pectoral-fin length 16.0% SL; distinctly humped nuchal profile; 1 branched dorsal-fin ray; body depth at anus 16.0% SL; 54 anal-fin rays; caudal peduncle depth 5.7% SL; caudal fin asymmetrically forked, with 12 principal rays and upper lobe 1.1 times longer than lower lobe; and 50 vertebrae. Clarias rennyae (Clariidae), new species, is distinguished from all Southeast Asian congeners in having a combination of characters: anal-fin length 51.3–56.3% SL; body depth at anus 13.1–13.7% SL; head width 17.9–18.9% SL; distance between occipital process and dorsal-fin origin 6.8–8.9% SL; frontal fontanelle length 17.7–22.5% HL; anterior edge of pectoral spine with 19–31 irregular tiny asperities; and 65–68 total vertebrae. Both new species appear to be endemic to blackwater streams along the western coast of Pulau Natuna Besar.

Two new camaenid species, Entadella concava, new species, and Entadella kilchomani Páll-Gergely, new species, are described from northern Vietnam. Both are known from their respective type localities only. The reproductive anatomy of the latter species is described and illustrated, with special attention on the inner structures of genital organs. This species is anatomically characterised by a strongly developed flagellum with a pointed tip and a blunt, caecum-like tip.