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The small, eyeless beetles of the genus Anillinus Casey (Coleoptera: Carabidae: Trechinae: Anillini) comprise a diverse, ubiquitous, but poorly known component of insect biodiversity in the southeastern United States. Their limited dispersal capabilities make them ideal subjects for biogeography, but taxonomic problems and undescribed species diversity hamper such studies. In this paper, we redescribe four enigmatic species, Anillinus docwatsoni Sokolov and Carlton, Anillinus elongatus Jeannel, Anillinus pecki Giachino, and Anillinus turneri Jeannel, and consider their relationships. The elongatus species group is revised, with descriptions of four newly discovered species, Anillinus arenicollis Harden and Caterino, new species, Anillinus montrex Harden and Caterino, new species, Anillinus pittsylvanicus Harden and Caterino, new species, and Anillinus uwharrie Harden and Caterino, new species. Two species previously considered part of the elongatus group are determined to not belong here, Anillinus cavicola Sokolov and Anillinus turneri Jeannel. The exact placement of A. turneri remains uncertain, but it shares some character states with the sinuaticollis group. We erect the pecki group for A. docwatsoni and A. pecki, which are likely sister species. We provide a key to the eastern species groups of Anillinus and the species of the elongatus and pecki species groups. Anillinus pecki is broadly distributed in the southern Appalachian Mountains northeast of the French Broad River basin, while A. docwatsoni is apparently endemic to the Hickory Nut Gorge in western North Carolina. Anillinus pecki is reported for the first time from Tennessee and Virginia. All members of the elongatus group have small geographic ranges and are difficult to sample without special techniques, hinting that many more species await discovery in the densely populated Piedmont region of North Carolina, where natural habitats are rapidly being lost. Our sampling was not dense enough to test biogeographic hypotheses, but distributions of the elongatus group species suggest that hydrochory might have played an important role in passive dispersal and reproductive isolation. These taxonomic contributions will facilitate future studies on the genus and serve to highlight the rich insect biodiversity that remains to be discovered in the southeastern United States. 

The fauna of Diplura, the two-pronged bristletails (Hexapoda), of the southern Appalachians has received little focused systematic attention. Existing literature suggests the fauna to comprise around a dozen species. Based on a broader DNA barcode-based survey of high elevation litter arthropods in the region, we suggest the fauna to be much richer, with automated species delimitation methods hypothesising as many as 35 species, most highly restricted to single or closely proximate localities. Such a result should not be very surprising for such small, flightless arthropods, although it remains to be seen if other markers or morphology support such high diversity. The region still remains sparsely sampled for these more cryptic elements of the arthropod fauna and much larger numbers of species undoubtedly remain to be discovered. 

Abstract The terrestrial isopod genusLigidiumincludes 58 species from Europe, Asia, and North America. In Eastern North America four species are recognized:L. floridanumandL. mucronatum, known just from their type localities in Florida and Louisiana respectively,L. blueridgensis, endemic to the southern Appalachians, andL. elrodii, widespread from Georgia to Ontario. The genus shows a marked morphological conservatism, and species are differentiated mostly by small morphological differences; it is not always easy to determine if such variability represents inter‐ or intraspecific variation. Here, we explore the diversity ofLigidiumfrom the southern Appalachian Mountains, exploring the congruence of morphologically defined groups with multilocus phylogenetic reconstructions and molecular species delimitation methods. We have studied a total of 130 specimens from 37 localities, mostly from the southern Appalachians, and analysed mtDNA (Cox1) and nuclear (28S, NaK) sequences. Morphologically, we recognized eight morphotypes, most of them assignable to current concepts ofL.elrodiiandL.blueridgensis. Phylogenetic analyses supported the evolutionary independence of all morphotypes, and suggest the existence of 8–9 species, including limited cryptic diversity. Single‐locus delimitation analyses based on mtDNA data suggest the existence of a much higher number of species than the multilocus analyses. The estimated age of the ancestors of sampled lineages indicates a long presence of the genus in eastern North America and old speciation events through the Miocene. Our results indicate a higher diversity than previously thought among theLigidiumpopulations present in the southern Appalachian Mountains, with several species to be described. 

Species of the genusLathrobiumGravenhorst (Coleoptera: Staphylinidae: Paederinae) from North America north of Mexico are reviewed and 41 species are recognized. Morphology and mitochondrial COI sequence data were used to guide species designations in three flightless lineages endemic to the southern Appalachian Mountains, a biologically diverse region known for cryptic diversity. Using a combination of phylogeny, algorithm-based species delimitation analyses, and genitalic morphology, five new cryptic species are described and possible biogeographic scenarios for their speciation hypothesized:L. balsamenseHaberski & Caterino,sp. nov.,L. camplyacraHaberski & Caterino,sp. nov.,L. islaeHaberski & Caterino,sp. nov.,L. lividumHaberski & Caterino,sp. nov.,L. smokienseHaberski & Caterino,sp. nov.Five additional species are described:L. absconditumHaberski & Caterino,sp. nov.,L. hardeniHaberski & Caterino,sp. nov.,L. lapidumHaberski & Caterino,sp. nov.,L. solumHaberski & Caterino,sp. nov., andL. thompsonorumHaberski & Caterino,sp. nov.Two species are transferred fromLathrobiumtoPseudolathraCasey:Pseudolathra parcum(LeConte, 1880),comb. nov.andPseudolathra texana(Casey, 1905),comb. nov.Twenty-six names are reduced to synonymy. Lectotypes are designated for 47 species. Larvae are described where known, and characters of possible diagnostic value are summarized. Species diagnoses, distributions, illustrations of male and female genitalia, and a key toLathrobiumspecies known from the Nearctic region (including several introduced species) are provided. 

Elevation gradients provide a wealth of habitats for a wide variety of organisms. The southern Appalachian Mountains in eastern United States are known for their high biodiversity and rates of endemism in arthropods, including in high-elevation leaf-litter taxa that are often found nowhere else on earth. Trechus Clairville (Coleoptera: Carabidae) is a genus of litter inhabitants with a near-global distribution and over 50 Appalachian species. These span two subgenera, Trechus s. str. and Microtrechus Jeannel, largely restricted to north and south of the Asheville basin, respectively. Understanding the diversification of these 3–5 mm flightless beetles through geological time can provide insights into how the litter-arthropod community has responded to historical environments, and how they may react to current and future climate change. We identified beetles morphologically and sequenced six genes to reconstruct a phylogeny of the Appalachian Trechus. We confirmed the Asheville Basin as a biogeographical barrier with a split between the north and south occurring towards the end of the Pliocene. Finer scale biogeography, including mountain-range occupancy, was not a reliable indication of relatedness, with group ranges overlapping and many instances of species-, species group-, and subgeneric sympatry. This may be because of the recent divergence between modern species and species groups. Extensive taxonomic revision of the group is required for Trechus to be useful as a bioindicator, but their high population density and speciose nature make them worth additional time and resources. 

The Pseudoscorpiones fauna of North America is diverse, but in regions like the southern Appalachian Mountains, they are still poorly documented with respect to their species diversity, distributions and ecology. Several families have been reported from these mountains and neighbouring areas. Here we analyse barcoding data of 136 specimens collected in leaf litter, most of them from high-elevation coniferous forest. We used ASAP as a species delimitation method to obtain an estimation of the number of species present in the region. For this and based on interspecific genetic distance values previously reported in Pseudoscorpions, we considered three different genetic Kimura two-parameter distance thresholds (3%/5%/8%), to produce more or less conservative estimates. These distance thresholds resulted in 64/47/27 distinct potential species representing the families Chthoniidae (33/22/12 species) and Neobisiidae (31/25/15) and at least six different genera within them. The diversity pattern seems to be affected by the Asheville Depression, a major biogeographic barrier in this area, with a higher diversity to the west of this geographic feature, particularly within the family Neobisiidae. The absence of representatives from other families amongst our studied samples may be explained by differences in their ecological requirements and occupation of different microhabitats. 

Medon icarus Caterino, new species (Staphylinidae: Paederinae) is described, restricted largely to the highest elevations of the southern Appalachian Mountains, USA. This flightless species occurs across several high ranges in the region, and analysis of COI sequences from known populations reveals deep genetic divergences among them. Insufficient morphological differentiation has been observed to subdivide them, but the possibility remains that this represents a cryptic species complex, with from 5–12 genetically but otherwise indistinguishable members. This is the only member of this mainly western Nearctic and Palearctic genus in the southeastern US, though it appears to be closely related to the northeastern winged species Medon americanus Casey. Description of DNA-associated larval specimens, along with adult morphological and molecular information, will help determine its position among global Medonina diversity. 

The higher elevations of the southern Appalachian Mountains, U.S.A., host a rich, but little-studied fauna of Proturan hexapods. Here, we publish 117 Proturan barcode sequences from this region, estimated by automated species delimitation methods to represent 72 distinct species, whereas only nine species have previously been reported from the region. Two families, Eosentomidae and Acerentomidae, co-occur at most sampling sites, with as many as five species occurring in sympatry. Most populations exhibit very low haplotype diversity, but divergences amongst populations and amongst closely-related species are very high, a finding common to other phylogeographic studies of Proturans. Though we were unable to identify any of the barcodes to species, they form a useful, if preliminary, glimpse of southern Appalachian Proturan diversity. 

Dipara trilineata (Diparidae) is a widespread eastern North American parasitoid with apterous females and winged males. Despite its seemingly limited dispersal capabilities, phylogeographic analysis over southern Appalachia reveals little structure, with only limited population level isolation. DNA barcoding surveys also definitively associate the male of the species, which had previously been misattributed, and a description of the correctly associated male is provided. 

HorologionValentine, one of the rarest and most enigmatic carabid beetle genera in the world, was until now known only from the holotype ofHorologion speokoitesValentine, discovered in 1931 in a small cave in West Virginia. A single specimen of a new species from Virginia was collected in 1991, but overlooked until 2018. DNA sequence data from specimens of this new species,Horologion hubbardisp. nov., collected in 2022 and 2023, as well as a critical examination of the external morphology of both species, allow us to confidently placeHorologionin the supertribe Trechitae, within a clade containing Bembidarenini and Trechini. A more specific placement as sister to the Gondwanan Bembidarenini is supported by DNA sequence data. Previous hypotheses placingHorologionin or near the tribes Anillini, Tachyini, Trechini, Patrobini, and Psydrini are rejected. The existence of two species ofHorologionon opposite sides of the high mountains of the middle Appalachians suggests that these mountains are where the ancestralHorologionpopulations dispersed from, and predicts the discovery of additional populations and species. All specimens ofH. hubbardiwere collected in or near drip pools, and most were found dead, suggesting that the terrestrial epikarst, rather than caves, is the true habitat ofHorologion, which explains their extreme rarity since epikarst has not been directly sampled. We recognize the tribe Horologionini, a relict lineage without any close relatives known in the Northern Hemisphere, and an important part of Appalachian biodiversity.