Rarely collected, Collartidini (4 genera, 14 species) are a tribe of Emesinae (Hemiptera: Heteroptera: Reduviidae), the thread legged assassin bugs, that have retained a number of plesiomorphic features within Emesinae. The group has long been believed to be restricted to equatorial Africa, Madagascar, and Sri Lanka, with more recent additions from the Canary Islands, Sudan, Israel, and Taiwan, and a fossil species from Baltic amber. The discovery of two undescribed species from Thailand and Malaysia (Borneo) has created the need for a reassessment of genera within Collartidini. We analysed a morphological matrix of 25 characters and 11 ingroup species that represents the four collartidine genera, finding that while Collartida Villiers, 1949 is recovered as monophyletic, Collarhamphus Putshkov & Popov, 1995 and Stenorhamphus Elkins, 1962 render Mangabea Villiers, 1970 paraphyletic. We here synonymise the fossil genus Collarhamphus and extant genera Mangabea and Stenorhamphus,provide a revised diagnosis and description of Stenorhamphus, and describe Stenorhamphus segerak,new speciesand S. phuphan,new species,from Malaysia (Sarawak) and Thailand, respectively. Lateral and dorsal habitus images as well as images of diagnostic characters are provided. A map showing the known distribution of Stenorhamphus spp.is provided, in addition to images highlighting diagnostic genus and species level characters.

Nemateleotris lavandula, new species, is described on the basis of the holotype from Augulupelu Reef, Palau, and twelve paratypes from across the western and central Pacific Ocean, including Fiji, Guam, Japan, and the Marshall Islands. The new species was previously confused with Nemateleotris helfrichi, but molecular analysis of mitochondrial COI reveals a difference of 1% in sequence data between both species, in addition to differences in morphometric measurements, live, and preserved colouration details. Both species are allopatric and do not overlap in distribution. The new species is readily separated from all congeners based on the following combination of characters: body lavender to lilac in life; maxilla unmarked, bright yellow in life; caudal fin truncate to weakly emarginate, unmarked, pale yellowish green in life; and snout, lower jaw, preopercle, and postorbital region bright yellow in life. We comment on the relationships among species of Nemateleotris, the taxonomic status of N. exquisita, and the doubtful identity of Zagadkogobius ourlazon. A revised key to species of Nemateleotris is provided.