Taxonomic notes on the crab-spider genera Nyctimus Thorell, 1877 and Zametopina Simon, 1909 (Araneae, Thomisidae) with descriptions of six new species from Southeast Asia

The crab-spider genera <i>Zametopina</i> Simon, 1909 and <i>Nyctimus</i> Thorell, 1877 remain poorly studied, with significant gaps in their taxonomic understanding. <i>Nyctimus</i> has seen little study since its original description, and species assignments remain uncertain due to a lack of modern diagnostic data. By contrast, <i>Zametopina</i>, historically monotypic, was recently expanded with a second species (<i>Z. wanliae</i> Lin & Li, 2023) following a redescription of the type species, <i>Z. calceata</i> Simon, 1909. Our study presents a review of these genera, primarily based on specimens collected from tropical Asia by the late Christa L. Deeleman-Reinhold as well as from the EFForTS project in the lowlands of Sumatra, Indonesia. The review includes the description of the following six new species: <i>Nyctimus falcatus</i> Benjamin & Dhiya'ulhaq, <b>sp. nov.</b> (♂), <i>Nyctimus kinabaluensis</i> Benjamin & Dhiya'ulhaq, <b>sp. nov.</b> (♂♀), <i>Nyctimus mutilloides</i> Benjamin & Dhiya'ulhaq, <b>sp. nov.</b> (♂), <i>Nyctimus quadripunctatus</i> Dhiya'ulhaq & Benjamin, <b>sp. nov.</b> (♂♀), <i>Nyctimus rendang</i> Dhiya'ulhaq & Benjamin, <b>sp. nov.</b> (♂♀), and <i>Nyctimus saksang</i> Dhiya'ulhaq & Benjamin, <b>sp. nov.</b> (♂). <i>Nyctimus bistriatus</i> Thorell, 1877 is redescribed and new locality records are provided. <i>Zametopina wanliae</i> is recorded for the first time outside of Vietnam. Further, updated species descriptions of <i>Nyctimus</i> and <i>Zametopina</i> are provided, along with taxonomic clarifications of the genera. This study emphasises the fundamental importance of well-curated, historical collections and ongoing fieldwork in resolving the systematics of lesser-known arachnid lineages.