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DNA barcoding was intended as a means to provide species-level identifications through associating DNA sequences from unknown specimens to those from curated reference specimens. Although barcodes were not designed for phylogenetics, they can be beneficial to the completion of the Tree of Life. The barcode database for Trichoptera is relatively comprehensive, with data from every family, approximately two-thirds of the genera, and one-third of the described species. Most Trichoptera, as with most of life's species, have never been subjected to any formal phylogenetic analysis. Here, we present a phylogeny with over 16 000 unique haplotypes as a working hypothesis that can be updated as our estimates improve. We suggest a strategy of implementing constrained tree searches, which allow larger datasets to dictate the backbone phylogeny, while the barcode data fill out the tips of the tree. We also discuss how this phylogeny could be used to focus taxonomic attention on ambiguous species boundaries and hidden biodiversity. We suggest that systematists continue to differentiate between 'Barcode Index Numbers' (BINs) and 'species' that have been formally described. Each has utility, but they are not synonyms. We highlight examples of integrative taxonomy, using both barcodes and morphology for species description.This article is part of the themed issue 'From DNA barcodes to biomes'.

Three new species of Trichosetodes, namely T. carmelae sp. nov., T. katiengensis sp. nov. and T. ratanakiriensis sp. nov. are described and illustrated by male specimens. The male genitalia of T. carmelae sp. nov. can be distinguished from the other 16 species of the genus found in Southeast Asia by the shape of the phallicata. The phallicata of T. carmelae sp. nov. bears a tuft of long hairs in the middle of the dorsal edge. Trichosetodes katiengensis sp. nov. can be distinguished from the other species in Southeast Asia by the shape of the phallicata which is divided into dorsal and ventral branches in lateral view, and T. ratanakiriensis sp. nov. by the characters of the left inferior appendage and the shape of segment IX. The posterior end of the left inferior appendage of T. ratanakiriensis sp. nov. is not forked and the ventral and lateral views of the posteroventral lobes of segment IX are rounded. Illustrations of male genitalia of Trichosetodes kampongspeuensis Malicky & Kong, 2020 are provided for comparison. The molecular diversity of new Trichosetodes species was analyzed using the mitochondrial large subunit ribosomal rRNA gene region (16S rRNA). In terms of their genetic divergence, T. ratanakiriensis sp. nov. and T. kampongspeuensis exhibited remarkable proximity, with only a 1.4% distance. On the contrary, T. carmelae sp. nov. displayed genetic disparity exceeding 6.3% when compared to both T. ratanakiriensis sp. nov. and T. kampongspeuensis. [ABSTRACT FROM AUTHOR]