The success story of Labiobaetis Novikova & Kluge in the Philippines (Ephemeroptera, Baetidae), with description of 18 new species.

Material collected between 1994 and 2020 in the Philippines, covering most main islands like Luzon, Mindoro, Palawan, Negros, Cebu, Leyte, and Mindanao and some smaller islands, substantially increased our knowledge of Labiobaetis Novikova & Kluge in this archipelago. Only three species were previously reported: L. molawinensis (Müller-Liebenau, 1982) and L. sumigarensis (Müller-Liebenau, 1982) from larvae and L. boettgeri (Ulmer, 1924) from adults. Eighteen new species have been identified using a combination of morphology and genetic distance (COI, Kimura 2-parameter). They are described and illustrated based on their larvae and a key to all species in the Philippines is provided. The total number of Labiobaetis in the Philippines has increased to 21 species. Additional diversity of Labiobaetis based on molecular evidence only is presented as Molecular Operational Taxonomic Units (MOTUs) without description. The interspecific K2P distances in the Philippines are between 15% and 27%, the intraspecific distances are usually between 0% and 3%. The total number of Labiobaetis species worldwide is augmented to 144. Thomas Kaltenbach, Jhoana Garces, Jean-Luc Gattolliat.