Material collected between 1999 and 2011 in Papua New Guinea and the Papua Province of Indonesia unveiled the enormous diversity of Labiobaetis on this island. Twenty-six new species were identified and delimited by integrative taxonomy using genetic distance (COI, Kimura-2-parameter) and morphology. These new species are described and illustrated based on larvae, augmenting the total number of Labiobaetis species on the island of New Guinea to 32. Seven morpho-groups of species are proposed based on morphological characters and a key to all New Guinea species is provided. The generic attributes of the larvae are summarised and slightly modified based on the examinations of the new species. Results on the genetics of most species (COI) are also provided. The interspecific K2P distances are between 13% and 32%, the intraspecific distances usually between 0% and 2%. Possible reasons for the remarkable richness of this genus in New Guinea are discussed.
Keywords: COI; Indonesia; Papua New Guinea; morphology; new species; species delimitation.