Gene rearrangement of the mitochondrial genome of insects, especially the rearrangement of protein-coding genes, has long been a hot topic for entomologists. Although mitochondrial gene rearrangement is common within Annulipalpia, protein-coding gene rearrangement is relatively rare. As the largest family in Annulipalpia, the available mitogenomes from Hydropsychidae Curtis, 1835 are scarce, and thus restrict our interpretation of the mitogenome characteristic. In this study, we obtained 19 novel mitogenomes of Hydropsychidae, of which the mitogenomes of the genus Arctopsyche are published for the first time. Coupled with published hydropsychid mitogenome, we analyzed the nucleotide composition evolutionary rates and gene rearrangements of the mitogenomes among subfamilies. As a result, we found two novel gene rearrangement patterns within Hydropsychidae, including rearrangement of protein-coding genes. Meanwhile, our results consider that the protein-coding gene arrangement of Potamyia can be interpreted by the tandem duplication/random loss (TDRL) model. In addition, the phylogenetic relationships within Hydropsychidae constructed by two strategies (Bayesian inference and maximum likelihood) strongly support the monophyly of Arctopscychinae, Diplectroninae, Hydropsychinae, and Macronematinae. Our study provides new insights into the mechanisms and patterns of mitogenome rearrangements in Hydropsychidae.

Adults and larvae of the genus Hydropsyche from Yun-nan and Si-chuan Provinces, China, were examined and the COI barcode gene sequences were obtained and analyzed, adults and larvae of 3 species were successfully associated. Of them, H. uvana Mey 1995 is a new record for the Chinese caddisfly fauna. The larvae of H. cerva Li & Tian 1990, H. penicillata Martynov 1931, and H. uvana Mey 1995 are described for the first time. The diagnostic features of the species are described and illustrated.

Fifty individuals of Limnephilus from the Qinghai Province, China, were examined, and their COI barcode sequences were extracted and analyzed. Forty individuals of Limnephilus from the Insect Collection of Nanjing Agricultural University (ICNAU), China, were examined, and photos of the male genitalia of four Limnephilus species are here presented. The males, females, larvae, and pupae of a new species, Limnephilus deqianensis n. sp., associated via COI barcode sequences, are described and illustrated. Ecological photos of the male, pupal case, and the habitat of the new species L. deqianensis n. sp. are also provided. Five species groups containing all seventeen Chinese Limnephilus species are revised. Diagnoses, keys, and a distribution map of them are provided. All of the sequences have been uploaded to GenBank. All specimens are deposited in the ICNAU, Nanjing, Jiangsu Province, P. R. China.