A new scuttle fly species, Microselia rossica sp. nov. (Diptera: Phoridae), a parasitoid of the ant species Camponotus vagus (Scopoli, 1763), is described from the floodplain habitats of the Rostov Province in southern European Russia. This is the first confirmed case of parasitisation by scuttle flies of worker ants in Russia. The behaviour of the females of the new species attacking the ants is described.

An annotated checklist of Lonchaeidae (Diptera) of the Republic of Mordovia (European Russia) is provided based on the materials collected from 2019 to 2021 mainly in beer traps at fixed heights in the forest canopy and with a Malaise trap. In total, 3254 specimens were examined, of which 2004 were identifiable to species level providing the records of 29 species in five genera. We have found 18 species of Lonchaeidae new to the fauna of Mordovia. Lonchaea cervisiae sp. nov. is described as new to science and L. fraxina MacGowan et Rotheray, 2000 is recorded as new to Russia. Earomyia mordovia MacGowan et Ruchin, 2022, syn. nov., is synonymised with E. schistopyga Collin, 1953.

Pleurobrachia Fleming, 1822 is the native taxon of ctenophores in the Black Sea. Until now, its species affiliation has not been resolved: the Black Sea Pleurobrachia is referred to either P. pileus (O.F. Müller, 1776) or P. rhodopis (Chun, 1879). In the taxonomic reviews, both species are recognised as occurring in the Black Sea. The experts on zooplankton identified the Black Sea Pleurobrachia based solely on its definitive body size, but size cannot be a sufficient diagnostic feature. To clarify the species identity of the Black Sea Pleurobrachia, we carried out a phylogenetic analysis using the nucleotide sequences of the mitochondrial COI and the nuclear 18S rRNA gene fragments. As a result, we have established that the Black Sea Pleurobrachia is P. pileus and its identification as P. rhodopis in the global taxonomic databases is erroneous.

Cylichna inflata sp. nov. is described based on nine specimens collected in 1931 in the Tatar Strait (northern part of the Sea of Japan) at a depth of 69 m. The new species differs from other species of the genus in the morphology of the shell, radula, gizzard plates, and in the presence of a seminal vesicle in the copulatory apparatus. The shell proportions of C. inflata sp. nov. are similar to those of some species of the genus Cylichnoides Minichev, 1977. The emended diagnoses of Cylichna Lovén, 1846 and Cylichnoides (Eoscaphandridae) are provided.

A new nematode species, Labronema przhiboroi sp. nov., belonging to the family Dorylaimidae, has been found in the freshwater Lake Duluk on the Putorana Plateau in Eastern Siberia, at a depth of approximately one metre. This species is morphologically similar to the Far Eastern species L. macrosoma Alekseev, 1992, from which it can be distinguished by its smaller body size, shorter spicules, and more pronounced cuticular ridges.

The taxonomic history of the subgenus Mellicta Billberg, 1820 of the genus Melitaea Fabricius, 1807 is reviewed. The names Mediomellicta Lastukhin, 2003, syn.nov., Monomellicta Lastukhin, 2003, syn. nov., Neomellicta Lastukhin, 2003, syn. nov., Oreomellicta Lastukhin, 2003, syn. nov., Paramellicta Lastukhin, 2003, syn. nov., Polymellicta Lastukhin, 2003, syn. nov., and Promellicta Lastukhin, 2003, syn. nov., are synonymised with Mellicta.

New data on the morphology, distribution and host plants are provided for several species of tephritid flies. Urophora xanthippe (Munro, 1934) is recorded for the first time from Russia and U. doganlari Kütük, 2006, from Armenia; U. kasachstanica (Richter, 1964) is recorded for the first time for the Volgograd and Samara provinces of Russia. The details of the male genitalia not included in the descriptions of U. doganlari, U. kasachstanica, U. terebrans (Loew, 1844), and U. xanthippe are figured. Centaurea polypodiifolia Boiss. is recorded for the first time as a host plant of U. doganlari. Jurinea squarrosa Fisch. et C.A. Mey. and Scorzonera rigida Auch. ex DC. are new hosts of Acanthiophilus helianthi (Rossi, 1794) and Trupanea stellata (Fuessly, 1775), respectively. Onopordum armenum Grossh. is a new host plant of Tephritis postica (Loew, 1844).

Sphenoptera (Deudora) polaceki sp. nov. from the Eastern Mediterranean (Bulgaria, Turkey and Greece) is described and compared with closely related species. Sphenoptera (Deudora) tamerlani Obenberger, 1929 is recorded for the first time from Tajikistan.

Eight new species of the family Dipluridae from the genera Masteria L. Koch, 1873, Striamea Raven, 1981 and Linothele Karsch, 1879 are diagnosed and described from the western central region of Colombia: Masteria verdum sp. nov. (both sexes), M. luisi sp. nov. (both sexes), Striamea kimbanai sp. nov. (both sexes), Linothele sanuk sp. nov. (both sexes), L. montana sp. nov. (both sexes), L. hunahpuisp. nov. (both sexes), L. ixbalanquei sp. nov. (female), and L. guarato sp. nov. (female). Additionally, L. tsachilas Dupérré et Tapia, 2015 and L. archidona Dupérré et Tapia, 2023 are reported in Colombia for the first time. The above-mentioned species were found in the departments of Risaralda, Tolima, Quindío, Valle del Cauca, and Putumayo of Colombia.

A histological study of the unique bathypelagic species Protoheterokrohnia bogutskayae Kassatkina, 2016 (Chaetognatha: Tokiokaispadellidae) was conducted. Specimens were collected from the near-bottom layers of the Laptev Sea in the deep Arctic waters. The structure of the trunk–tail region was examined, revealing that large lateral fields are characteristic of this plankto-benthic species. The intestinal structure differs from that of other chaetognaths, with the intestinal epithelium containing secretory cells with an unusual secretion containing crystal inclusions. The composition and location of the female and male gonads were also studied. The longitudinal muscles were investigated using immunocytochemical method, which revealed the presence of type IV collagen in the extracellular matrix at the base of the muscle layer. The structure and location of the transverse muscle bundles and their attachment points were described in detail. Fins and fin rays were analysed through histological sections, showing that fin rays are located within the cytoplasm of the fin epithelial cells as cytoplasmic inclusions containing proteins. The fin rays are notably long, as illustrated in the longitudinal sections. The dense arrangement of the rays is characteristic of the species examined.

Three species of stolidobranch ascidians, Asajirus arcticus (Hartmeyer, 1923), Eugyrioides pedunculatus (Traustedt, 1886), comb. nov., and Kukenthalia borealis Hartmeyer, 1903 are recorded from the deep waters of the Arctic Ocean for the first time and are briefly described based on new material. The nomenclature of the involved ascidian taxa is discussed. It is shown that Eugyra Hancock, 1870 (Ascidiacea) is preoccupied by Eugyra Fromentel, 1857 (Anthozoa) and that the valid generic name for ascidians currently assigned to Eugyra is Eugyrioides Seeliger, 1907. The currently accepted subfamily name Polyzoinae Michaelsen, 1900 is invalid, as it is a junior synonym of Polystyelinae Herdman, 1886.

Three species of the genus Plateros Bourgeois, 1879—P. manaliensis (Bocáková, 1997), P. atrosuturalis Kazantsev, 2011, and P. gavryushini Kazantsev, 2017—previously known only from northern India, northern Myanmar and Indochina, respectively, are reported from Nepal for the first time. Plateros anguliplanatus Kazantsev, 2021, syn. nov. is synonymised with P. gurkha Kazantsev, 2001. Fourteen species of Plateros from Nepal—P. atrosuturalis Kazantsev, 2011, P. brancuccii Kazantsev, 1991, P. cimicoides Kleine, 1928, P. cinereus Kazantsev, 1991, P. dentifer Kazantsev, 1991, P. harmandi Bourgeois, 1928, P. karnaliensis Kazantsev, 2011, P. kumatai Nakane, 1983, P. laterculus Kazantsev, 1991, P. macrosuturalis Kazantsev, 1991, P. manaliensis (Bocáková, 1997), P. nepalensis Kazantsev, 1991, P. suturalis Pic, 1928, and P. wittmerianus Kazantsev, 1991—are illustrated with colour photographs of their habitus and aedeagi for the first time. A comprehensive list of Plateros species in Nepal is presented, now encompassing a total of 36 species.

Bembecia strandi (W. Kozhantschikov, 1936) is redescribed based on the new material collected from the type locality and the type specimens (lectotype and paralectotype). A detailed analysis of the external morphology, as well as the structures of the genitalia of both males and females, showed that this species is very close to B. sareptana (Bartel, 1912), but is quite clearly distinguished from it by the coloration of some parts of the body and the structure of the transparent areas of the forewing. In addition, these two species have slight differences in the structure of the genitalia of both males and females.

The Mexican species of the genus Eusterinx Förster, 1869 are reviewed. A new replacement name E. americana nom. nov. is proposed for E. arcuata Dasch, 1992. Nine Eusterinx species are now known from Mexico, including a new species, E. (Eusterinx) apicicornis sp. nov., described herein. The previously unknown male of E. madorae Khalaim et Kasparyan, 2018 is described. The Nearctic and Neotropical species E. solida Dasch, 1992 is tentatively placed in the subgenus Ischyracis Förster, 1869. A key to nine species of Eusterinx occurring in Mexico is provided.

Cyathocotyle Mühling, 1896 is a genus of primitive diplostomoid digeneans parasitising birds. The results of recent studies suggest that this taxon is paraphyletic, which means that further phylogenetic assessment of species assigned to Cyathocotyle is necessary. In this study, two species, C. bithyniae Sudarikov, 1974 and C. fulicae Ginetzinskaja, 1952, from the Eurasian Coot (Fulica atra Linnaeus, 1758) are characterised based on morphological and molecular data. For C. fulicae, the size of the testes and the cirrus sac are clarified, and the presence of a poorly developed ventral concavity and the tegumental scale-like spines is noted. This study is the first report of infection of a bird host by C. bithyniae in nature. The new molecular data confirm the paraphyletic status of Cyathocotyle. The obtained results suggest that C. bithyniae is conspecific with an isolate of C. bushiensis Khan, 1962 molecularly characterised by Achatz et al. in 2019, and C. fulicae is conspecific with cyathocotylid cercariae previously found in Bithynia tentaculata (Linnaeus, 1758) from Central Europe.

In 2016, during a study of temporary wetlands in Kazan (Middle Volga region, Russia), a new limnotyphloplanid microturbellarian species from the family Typhloplanidae, Krumbachia tatianae sp. nov., was found. This paper provides an illustrated description of the new species, including photographs and drawings that depict its external morphological characters and copulatory organs. Krumbachia tatianae sp. nov. differs from all other congeners in a combination of morphological characters: the presence of eyes, specific body pigmentation, a straight ejaculatory duct, a long seminal receptacle stalk, and the presence of an atrial sphincter.

Mature larvae of two species from the genus Austrelmis Brown, 1984 and one species from the genus Macrelmis Motschulsky, 1860 are described and illustrated for the first time: A. argentinensis Manzo et Archangelsky, 2015, A. tafi Manzo et Archangelsky, 2015, and M. aequalis (Hinton, 1937). A comparison of the larvae of these species with the described larvae of other species from their respective genera is provided. Additionally, information on the habitat and distribution of the examined species is included.

Syntypes of the Oriental species Porizon meridionalis Morley, 1913, deposited in the Museum of Genoa (Italy), have been examined. The species is found to be a distinct member of the genus Diaparsis Förster, 1869, resulting in the new combination Diaparsis (Diaparsis) meridionalis, comb. nov. The lectotype female from Myanmar is designated. Colour photographs, redescriptions of both the female and male, and remarks on the taxonomy of D. meridionalis are provided.

A new species of the genus Pelomyxa Greeff, 1874, P. seravini sp. nov., was isolated and described from the bottom sediments of freshwater bodies in north-western Russia. The morphology of P. seravini sp. nov. was examined using light microscopy, immunofluorescence microscopy, and transmission electron microscopy. Distinctive characters of the new species include a monopodial cell shape during locomotion, minimal cytoplasmic vacuolisation, the presence of three morphotypes of prokaryotic endocytobionts, and numerous lipid droplets within the cytoplasm. The main distinguishing characters of P. seravini sp. nov. relate to nuclear organisation: several peripheral intranuclear bodies and an association of the nuclear envelope with short microtubules. Based on morphological characters observable by light microscopy in representatives of the genus Pelomyxa, an identification key for currently known species is compiled.

The name Grammostola australis Gerschman et Schiapelli, 1948, syn. resurr. is herein resurrected from synonymy with G. inermis Mello-Leitão, 1941, based on morphological and molecular evidence. The holotypes of both species are redescribed, and the female of G. australis is described for the first time. Diagnoses of these species are also provided. Phylogenetic analyses recovered G. inermis as a distinct lineage from G. australis, suggesting that both species are more closely related to Brazilian and Uruguayan species of the genus Grammostola Simon, 1892, than to other Argentinean species. Similarly, Chilean species appear distinct from other Grammostola species, indicating that the Andes act as a geographical barrier.

A revision of the bush-cricket genus Anatlanticus Bey-Bienko, 1951 (Tettigoniidae: Drymadusini) is presented. The names A. longispeculi Liu, 2015, syn. nov. and A. liaoningensis Liu, 2015, syn. nov. are placed in synonymy with A. uvarovi (Miram, 1940). Brief redescriptions of A. uvarovi and A. koreanus Bey-Bienko, 1951, an updated diagnosis of the genus, and a key to the species are provided.

A new species of the genus Pagurapseudopsis Shiino, 1963 (Tanaidacea: Apseudomorpha: Pagurapseudopsididae), P. vietnamica sp. nov., is described from the mangrove swamps of the Cần Giờ Mangrove Biosphere Reserve in southern Vietnam. It is closely related to P. thailandica Angsupanich, 2001, which is known from Songkhla Lake (lagoon) in Thailand (Siam Bay), but can be clearly distinguished by the armature of the carpal segment of the male chelipeds. The density of the new species during the wet season (September–October 2023) is approximately 49 ± 17 individuals per square metre, making it the third most abundant tanaidacean species in these mangrove biotopes.

Psednos kaganovskii sp. nov. is described from the Emperor Seamount Chain. Based on fin ray and vertebral counts (39 dorsal and 35 anal fin rays, 47 total vertebrae), the new species belongs to the P. christinae species–group but differs from all other species in this group by the larger eye (35.7% of head length), heavily pigmented gastrointestinal duct, pectoral girdle structure, and a combination of other characters. This is the first record of the genus in the northwestern Pacific Ocean.

The genus Myopias Roger, 1861 is poorly known due to its cryptic lifestyle and nesting habits. Seven species of this genus have been recorded from Sumatra. A new, eighth species, M. paratenuis sp. nov. is described herein based on the worker caste. The new species is most similar to M. tenuis (Emery, 1900) from New Guinea, M. minima (Jaitrong et al., 2018) from Thailand, and M. suwannaphaki (Jaitrong et al., 2020) from Borneo.

The article provides a detailed, illustrated description of a new genus and species, Vedma circe gen. et sp. nov., belonging to the tribe Miscogastrini (Chalcidoidea: Pteromalidae: Miscogastrinae) from South Korea. The new genus is distinguished by the following combination of characters: a massive head; lower margin of the clypeus with three asymmetrical teeth; large, circular tentorial pits positioned on either side of the clypeus; a rounded and sloping pronotal collar; a mesosoma with complete, shallow, widely spaced notauli; and the forewing with a large stigma.

Paralecithodendrium ilei (Zdzitowiecki, 1969) is a rare parasite of European vespertilionid bats. Identification of this digenean species is difficult due to its high morphological similarity to closely related species. Specimens of P. ilei from the small intestine of the northern bat (Eptesicus nilssonii Schreber, 1774) inhabiting the Zhiguli State Nature Reserve (European Russia) were examined. The aim of this study was to analyse new material on P. ilei using both morphological and molecular phylogenetic approaches. Here, we provide a complete redescription of P. ilei from bats in European Russia, including the first molecular phylogenetic data based on 28S rRNA and cox1 mtDNA sequences. The results obtained confirm that this digenean species is distinct.

A new species of the genus Parahigginsia Dendy, 1924 from the southern slope of the underwater Piip Volcano in the western Bering Sea, found at a depth of 981 m, is described. Previously, only two species of this genus were known, P. phakelloides Dendy, 1924 from the South Pacific and P. strongylifera Van Soest, Meesters et Becking, 2014 from the Caribbean. The discovery of P. beringiensis sp. nov. in the North Pacific extends the known distribution and depth ranges of Parahigginsia. Morphological comparison of the species from this genus has been conducted. The results of morphological examination and sequencing of the 18S and 28S rRNA genes indicate that the new species belongs to the order Suberitida and, most likely, to the family Halichondriidae.

A new gall-inducing felt scale insect, Mendicus anachoreta Gavrilov-Zimin, gen. et sp. nov. (Homoptera: Coccinea: Eriococcidae), is described and illustrated based on specimens collected from conical galls on the leaves of Escallonia pulverulenta (Escalloniaceae) in Curicó Province, Chile. The new genus is monotypic and distinguished from all other eriococcid genera by the following combination of characters: the complete absence of tubular ducts; a partially reduced anal apparatus; and the presence of shagreen cuticle areas posterior to the hind coxae.

A new species of the tribe Similipepsini (Lepidoptera: Sesiidae: Tinthiinae), Milisipepsis baishaensis sp. nov., is described and illustrated from the vicinity of Lijiang in the Yunnan Province, China. The new species superficially resembles Milisipepsis yunnanensis (Špatenka et Arita, 1992) but differs in the configuration of the transparent areas of the forewing, the coloration of the abdomen, and certain details of the male genitalia.

The first record of the planktonic copepod Acanthodiaptomus pacificus (Burckhardt, 1913) (Calanoida: Diaptomidae) from the waters of the Darkhat Hollow in Mongolia is presented. The morphology of this species has been examined in detail for the first time using a scanning electron microscope; a complete description of the mouthparts is provided for the first time, and the description of the fifth leg in both males and females is supplemented. More reliable characters for differentiating males of A. pacificus and A. denticornis (Wierzejski, 1887) than those previously used are revealed. New diagnostic characters of the genus Acanthodiaptomus Kiefer, 1932 are proposed.

Mid-Cretaceous Burmese amber preserves an exceptionally diverse assemblage of operculate land snails. Here, two new diplommatinid species are described: Euthema convexispira Bichain et Páll-Gergely, sp. nov. and Eu. torokzselenszkyi Páll-Gergely et Szabó, sp. nov. Newly found specimens of two previously known species, Hirsuticyclus canaliculatus Yu, 2022 and Cretadiostoma caperatum Yu, Zhuo et Páll-Gergely, 2023, are described and illustrated; the specimen of the former is characterised by a distinctive spiral operculum, while that of the latter provides additional data on the morphology of the aperture and the proportions of the shell whorls. Furthermore, the article reports three specimens that are tentatively attributed here to the species Euthema cf. annae Balashov, 2021 and to the genera Euthema Yu, Wang et Pan, 2018 and Pulchraspira Yu, Salvador et Jarzembowski, 2021.

Bovichtus veneris Sauvage, 1879 is a poorly studied species endemic to St Paul Island in the Indian Ocean. External morphology, teeth, axial skeleton and seismosensory system of three type specimens from the Muséum national d’histoire naturelle in Paris and one specimen from the collection of the Zoological Institute of the Russian Academy of Sciences, St Petersburg, were studied. A scheme of the seismosensory system of B. veneris is given. The investigated characters of B. veneris are compared with those of other species of the genus Bovichtus Valenciennes, 1832. The following diagnostic characters of B. veneris are established: snout length is less than the diameter of the eye and less than 25% of head length; the first predorsal distance is 1.2–1.5 times the interpelvic distance; caudal peduncle is 11.0–11.4%, opercular spine is 14.4–17.8% of standard length; outer teeth on the upper jaw are slightly enlarged; coloration is monotonous, without pronounced spots and saddles.

The malacofauna of Lake Baikal is considered predominantly endemic. For example, the list of bivalve species inhabiting the littoral zone of this lake mainly comprises endemic representatives of the family Sphaeriidae. However, the absence of molecular data has hindered their precise identification. Here, the presence of the North Palaearctic fingernail clam Euglesa waldeni (Kuiper, 1975) in Lake Baikal is reported for the first time. This finding is confirmed using three molecular markers, including the Folmer fragment of the mitochondrial cytochrome c oxidase subunit I (COI), 16S rRNA, and ITS1. The phylogenetic relationships of Eu. waldeni and its congeners were estimated based on a maximum likelihood analysis of the COI marker. Morphological characteristics of Eu. waldeni collected from Lake Baikal are described, and individuals identified as sexually mature, with embryos at various developmental stages, have been documented. The population density of Eu. waldeni has been determined in the area around Ol’khon Island.

A new species, Ctenolepisma (Ctenolepisma) grandisetosum sp. nov., is described and illustrated based on the material collected in the Sultanate of Oman, near the southeastern coast of the Arabian Peninsula. The new species is closely related to C. (C.) turkestanicum Kaplin et Shakula, 2022 from southern Kazakhstan and the psammophilous species C. (C.) barchanicum Kaplin, 1985 from eastern Karakum (Turkmenistan), which have no median bristle combs on urosternites. The new species differs from them in the body length, the number of sensory papillae on apical segment of labial palps, bristle combs on thoracic sterna, chaetotaxy of the urosternites and urotergites, and the number of the urostyli.

To clarify the taxonomic status of the Reed Bunting, Emberiza schoeniclus Pallas, 1811, nesting in Eastern Ciscaucasia, comparative studies of key diagnostic characters were conducted on 48 specimens from the collection of the Zoological Institute of the Russian Academy of Sciences. A sample of specimens from Eastern Ciscaucasia was compared with three other samples from Western Ciscaucasia, the Volga Delta and western Kazakhstan, and the Lower Volga region, each comprising 12 specimens. For the statistical analysis of wing length and bill depth, the non-parametric Mann–Whitney U test was employed. Based on the visual examination of plumage coloration and morphometric diagnostic characters, the assignment of the Reed Bunting nesting in Eastern Ciscaucasia to the subspecies E. s. pyrrhuloides Pallas, 1811, has been reliably confirmed. The misattribution of these birds to the subspecies E. s. volgae Stresemann, 1919 is shown.

Three species described in the genus Halys Fabricius, 1803, but now considered incertae sedis—H. hedenborgi Stål, 1865 (distributed in Sudan and Eritrea), H. jizanus Linnavuori, 1986 (Saudi Arabia, Yemen), and H. persa Bergroth, 1919 (Iran, Afghanistan)—are transferred to the genus Salixocoris Ahmad et Abbasi, 1974. This decision is based on an analysis of the original descriptions and illustrations of three species from Pakistan, originally assigned to Salixocoris: S. peshawarensis Ahmad et Abbasi, 1974, S. sindellus Ahmad et Kamaluddin, 1978, and S. excavatus Memon et Shaikh, 2004, as well as on the examination of collection specimens and published descriptions and illustrations of the species previously regarded as incertae sedis. The fourth incertae sedis species, H. maculipennis Stål, 1865 (Guinea-­Bissau, Ivory Coast, Nigeria, Senegal), is placed in the new genus Ergamenes gen. nov., in which a new species, E. tetrodus sp. nov. from Sudan, is also described. The new genus is characterised by unique characters and a combination of characters that distinguish it from other members of the Halys genus–group. Illustrated redescriptions of S. hedenborgi, comb. nov., S. jizanus, comb. nov., and S. persa, comb. nov. are presented. The structure of the pygophore, paramere, completely inflated aedeagus, and the external and internal female terminalia of S. jizanus and S. persa is thoroughly described for the first time; for S. hedenborgi, the female terminalia are described for the first time, but most details of the male terminalia remain unknown. Salixocoris hedenborgi is recorded from Yemen for the first time.