New species of Labiobaetis Novikova & Kluge from Thailand (Ephemeroptera, Baetidae)

Investigations of material collected by one of us (CS) between May 2017 and November 2023 from 70 localities in Thailand further increases our knowledge of the diversity of the genus <i>Labiobaetis</i> Novikova & Kluge, 1987 in Thailand and Southeast Asia in general. Eleven species have been identified using a combination of morphological and molecular analysis (COI). Nine are new to science, they are described and illustrated based on their larvae, and in one case, complemented by the male imago. Two of the new species belong to the <i>L. batakorum</i> species group, <i>L. mon</i> <b>sp. nov.</b>, <i>L. lahu</i> <b>sp. nov.</b>; three to the <i>L. numeratus</i> species group, <i>L. tenasserimensis</i> <b>sp. nov.</b>, <i>L. angularis</i> <b>sp. nov.</b>, <i>L. tonsator</i> <b>sp. nov.</b>; one to the <i>L. operosus</i> species group, <i>L. nisaratae</i> <b>sp. nov.</b>, and three to the <i>L. sumigarensis</i> species group, <i>L. karen</i> <b>sp. nov.</b>, <i>L. septem</i> <b>sp. nov.</b>, <i>L. ranongensis</i> <b>sp. nov.</b> A key to all species of <i>Labiobaetis</i> from continental Southeast Asia is provided. Additionally, the genetic distances (COI; Kimura-2 parameter) including all species treated in this study are discussed. The total number of <i>Labiobaetis</i> species worldwide is augmented to approximately 170.