Stoneflies (Plecoptera) are known for being sensitive to water pollution and are used as bioindicators for evaluating water quality. Among them, Nemouridae, especially the genus Nemoura, which are commonly referred to as winter stoneflies, can be found around streams even during the cold winter months. Nemoura geei Wu, 1929, among them, was originally described from Beijing and is widely distributed in Korea, China, Japan, and the Russian Far East. Here, we report the development and characterization of new functional microsatellite markers of N. geei using high-throughput sequencing technology. A total of 80,661 microsatellite loci were identified with a total length of 1,801,591 bp. The average length was 22.34 bp, and microsatellites occupied 0.42% of the entire sequence. The novel 20 microsatellite markers developed in this study can be usefully applied to the population genetics analyses as important genetic resources for understanding the ecological and evolutionary characteristics of a stonefly species at the population level in Korea.

The family Baetidae is known to be the most species-rich family in the order Ephemeroptera. The genus Baetis contains up to 160 species, but members of the genus in East Asia are still poorly investigated. In this paper, Baetis spinoculis sp. nov., is described based on larval specimens collected in a stream of the Chiaksan mountain in Korea. While four species in the genus have been described in Korea: Baetis fuscatus (Linnaeus), B. silvaticus Kluge, B. pseudothermicus Kluge, and B. ursinus Kazlauskas, this new species is distinguished from other Korean baetid species by both genetic and morphological characteristics. B. spinoculis can be separated from the related B. pseudothermicus group by the COI genetic distant. The cuticle structures on paraproct plates and abdominal pigment patterns also distinguish B. spinoculis from B. pseudothermicus and other related species.

The mayfly genus Drunella is the most diverse genera in the family Ephemerellidae, and is found in lotic streams throughout East Asia and North America. The species D. ishiyamana is found widely throughout East Asia and their species concept has not been properly defined until recently. The D. ishiyamana species group was examined, and morphological and molecular evidence of a new species were uncovered. In this study Drunella punctata sp. nov. is formally described, mainly distinguished from D. ishiyamana by the lack of a notch in their median clypeal tubercle in their larval stage. Photographs, diagnosis, and descriptions of D. punctata are provided.

This research introduces the subfamily Catotrichinae to the South Korean fauna for the first time. Within the globally recognized 6,651 Cecidomyiidae species, only ten are categorized under the Catotrichinae subfamily. Notably, this subfamily, which ingests fungi during larval development, is among the most primordial lineages of the Cecidomyiidae, both in morphological and molecular terms. The species Catoricha nipponensis of Catotrichinae was newly observed in Yeongwol, Gangwon-do, in October 2021. It was recorded for the first time in Korea, with its holotype initially collected in Honshu, Japan, in November 1923. This study provides the diagnosis, photographs of distinguishing characteristics, and the DNA barcode sequences for Catotricha nipponensis. This work was supported by a grant from the National Institute of Biological Resources (NIBR), funded by the Ministry of Environment (MOE) of the Republic of Korea.

The genus Campylomyza Meigen, 1818, from the Micromyinae subfamily of the Cecidomyiidae, includes 40 known species globally. The genus Campylomyza has been primarily studied within the Palearctic region, with 39 species, 2 from the Nearctic region, and 1 from the Oriental region. As of now, four species have been documented in Korea: Campylomyza appendiculata, C. flavipes, C. furva, and C. spinata. Our research from 2017 to 2020 uncovered five previously unreported species in Korea (C. abjecta, C. aborigena, C. cornuta, C. cavitata, and C. cingulata) and introduces seven new species (C. angusta sp. nov., C. ambulata sp. nov., C. convexa sp. nov., C. cornigera sp. nov., C. hori sp. nov., C. odae sp. nov., and C. yeongyangensis sp. nov.). These findings are based on morphological evidence and DNA analysis. We present comprehensive data, including the mitochondrial COI sequences, diagnoses, detailed descriptions, and identification keys for these species. This work was supported by a grant from the National Institute of Biological Resources (NIBR), funded by the Ministry of Environment (MOE) of the Republic of Korea.

Neomyrhessus Minkina, 2024, is a rare genus comprising six species, recently erected from Myrhessus Balthasar, 1955 for N. nanjingensis. To date, all six species have been reported in East Asia, with five from Japan and one from China. In this study, the genus Neomyrhessus is recorded for the first time in South Korea, with the discovery of a new species Neomyrhessus coreanus sp. nov. Description, illustrations of morphological characters, and habitat information for a new species are provided.

The invasive red swamp crayfish, Procambarus clarkii, is native to southcentral United States and northeastern Mexico. Recently, it has been being spreading in the wild in South Korea. However, its primary sources, introduction routes, establishment, and expansion in South Korea remain unclear. Here, we analyzed genetic diversity and population genetic structures of its domestic natural populations during early invasion, commercial stock from local aquaria (a suspected introduction source), and original United States population using mitochondrial COI gene sequences for 267 individuals and eight microsatellite markers for 158 individuals. Natural and commercial populations of P. clarkii showed reduced genetic diversity (e.g., haplotype diversity and allelic richness). The highest genetic diversity was observed in one original source population based on both genetic markers. Despite a large number of individuals in commercial aquaria, we detected remarkably low genetic diversity and only three haplotypes among 226 individuals, suggesting an inbred population likely originating from a small founder group. Additionally, the low genetic diversity in the natural population indicates a small effective population size during early establishment of P. clarkii in South Korea. Interestingly, genetic differentiation between natural populations and the United States population was lower than that between natural populations and aquarium populations. This suggests that various genetic types from the United States likely have entered different domestic aquariums, leading to distinct natural populations through separate pathways. Results of our study will provide an insight on the level of genetic divergence and population differentiation during the initial stage of invasion of non-indigenous species into new environments.