A new species of the genus Acrossus Mulsant, 1842, Acrossus baeisp. nov. from South Korea, is described and illustrated on the basis of morphology and mitochondrial COI sequences. The species was compared with four related species; Acrossus atratus (Waterhouse, 1875), A. humerospinosus (Petrovitz, 1958), A. luridus (Fabricius, 1775), and A. superatratus (Nomura & Nakane, 1951). The taxonomic status and diagnostic characters of the new species are discussed. A key to species of the genus Acrossus in the Korean Peninsula is given.

Hydrochara affinis (Coleoptera: Hydrophilidae), a water scavenger beetle, was recently identified as a natural and effective agent for biological mosquito control; it was reported to exhibit high rates of mosquito larvae predation. However, maintaining the quality (i.e., natural ecological attributes, such as genetic variation) of laboratory-reared populations is essential for ensuring the long-term success of biological control programs. Accordingly, here, we aimed to use mitochondrial Cytochrome c oxidase subunit I (COI) sequences to document the genetic diversity, population structure, and phylogenetic position of natural and lab-reared H. affinis populations in South Korea and use geometric morphometric analysis to investigate the populations’ morphological divergence. The natural H. affinis populations possessed high genetic diversity and numerous COI haplotypes, suggesting that these populations were healthy and could be directly applied to mosquito habitats without alterations to their natural genetic attributes. The lab-reared populations also possessed high genetic diversity and, thus, the potential for high adaptive capacity to new environments. Although no distinct population genetic structures were observed, quantitative variation was observed in the body shape of both the natural and lab-reared populations. The high levels of genetic and morphologic variation observed in the H. affinis populations examined here indicate the species’ favorable conservation status, genetic diversity, adaptive capacity, and, thus, “suitability” for field application as an effective mosquito control agent.

Populations of Gymnopleurus mopsus (family Scarabaeidae), a dung beetle that displays dung-rolling behavior (i.e., a telecoprid), have recently experienced sharp declines, and many populations are now at high risk of local extinction. However, Mongolia, which constitutes a major portion of the species’ distribution, still sustains a relatively large population. Here, we used mitochondrial COI sequences to investigate the within-population genetic diversity and both the genetic and phylogeographic structures of 24 G. mopsus populations across the species’ main distribution in Mongolia. Several lines of evidence indicated that the phylogeographic structure of G. mopsus had been influenced by a recent and sudden demographic expansion. Interestingly, the expansion of Mongolia’s G. mopsus population corresponded to the advent of livestock domestication in the region, and the species’ genetic structure coincided with road networks, which presumably serve as migration routes for livestock that might mediate the beetle’s dispersal. In addition, we also found that G. mopsus possesses high levels of haplotype diversity, which is generally indicative of large effective population sizes (N_e). Overall, the present study contributes to the current understanding of G. mopsus’ demographic history and dispersal patterns and also provides valuable information for the species’ conservation and management.

Giant water bugs (Hemiptera: Belostomatidae) are top predators in wetland ecosystems, serving as biological indicators of the health of lentic ecosystems and as effective biological control agents for freshwater snails and mosquitoes. This study aimed to predict the current and future distribution of two Korean giant water bugs, Appasus japonicus and Diplonychus esakii, under three climate change scenarios, contributing to the sustainable management of wetland ecosystems in South Korea. Using MaxEnt models, we employed seven climatic and three non-climatic variables to investigate the habitat preferences and distribution patterns of the species. The results revealed that A. japonicus is likely to experience a northward range contraction due to climate change, while D. esakii is predicted to expand its distribution northward without losing its current range. These responses may lead to occupancy turnover between the two species, potentially driving reassembly in aquatic organism community. Elevation was the primary factor influencing the distribution of A. japonicus, whereas annual mean temperature was the most informative variable for D. esakii, both factors derived under the current climate conditions. These findings suggest that both species are highly sensitive to climate change, with potential range shifts toward higher latitudes and elevations. This study provides insights into how climate change could impact two giant water bugs, thereby supporting future efforts to manage and conserve wetland ecosystems in this country.

Diplonychus esakii, a water bug from the family Belostomatidae, plays an important role in freshwater ecosystems as one of the top predators. In this study, we investigated the genetic diversity and population structure of D. esakii by analyzing 318 specimens across 27 sites in South Korea. We found that the populations of D. esakii possess 11 haplotypes with a haplotype diversity of 0.623. This represents a relatively low level of genetic diversity compared to other known belostomatids and endangered species. AMOVA and F_ST analyses revealed significant genetic differentiation among populations, with most populations harboring only 1–2 haplotypes, suggesting restricted gene flow between populations and a low level of genetic diversity. This low genetic diversity and limited gene flow suggest a potential vulnerability to environmental changes and an increased risk of extinction, indicating that D. esakii should be designated as a protected species in South Korea as part of future conservation efforts. Based on the results of this study, Upo Wetland, which maintains relatively high levels of genetic diversity and Jeju Island, which, despite its lower genetic diversity compared to the mainland, does not share haplotypes with other regions, should be considered key conservation units for this species. This study highlights the importance of incorporating genetic information into conservation status assessments under the Red List Categories and Criteria and also emphasizes the need to evaluate this species on the Korean Red List. The data provided here will serve as essential baseline information and valuable resources for the development of effective conservation strategies.

The Coleopterists Bulletin publishes a wide variety of articles, notes, and book reviews regarding the biology, taxonomy and ecology of beetles (Coleoptera).