Records of the genus Zercoseius Berlese in North America are presented from British Columbia and Oregon, i n South America from Brazil and Ecuador, and in Europe from northern Europe and Spain. Its sister-grou p relationships with other genera of Blattisociidae are reviewed. The first description and illustration of a deutonymph reveals an ontogenetic autapomorphy for the genus, the anal shield enlarged to a ventrianal shield bearing more setae than the circumanal setae. Adult females of the Z. spathuliger species group are confirmed to have elements of a phytoseioid sperm access system. A revised diagnosis and description of Zercoseius are presented, along with an updated key to world genera and subgenera of the family Blattisociidae. Apart from the recently described, Neotropical Z. luizdequeiroz Santos et al., uncertainties persist as to whether only one species or a species group currently constitutes the type species of the genus. Nine species, including seven new species of that group are described and illustrated, with a key to those species, based on representatives from western North America and Europe.

A new soil-dwelling mite species, Zerconopsis sibiricus sp. nov., is described from Russia based on the females, males, and nymphs. It occurs in plain and mountain areas of Siberia and the Far East (27 localities), in tundra (Low Arctic) and taiga landscapes, including the area of the Cold Pole of the Northern Hemisphere. Another species, Zerconopsis michaeli Evans & Hyatt, 1960, is first reported from Denmark, Russia, Georgia, Turkey, Azerbaijan, and California, USA (23 new records). Its male, nymphs, and larva are first described, and the female description is corrected with illustrations. The range of Z. michaeli in the Old World can be considered as an Amphi-Palaearctic one, excluding areas with very cold and/or continental climates. This species dwells in forest litter, rotten wood, and bracket fungi; however, in Northern Europe almost all records are from arboreal (woody, fungal) habitats. The genus Zerconopsis Hull, 1918 now includes 19 described species from all continents except Africa and Antarctiсa. A revised generic diagnosis is provided, and three morpho-ecological species groups are recognised. A key for the five Zerconopsis species residing in Siberia is given.

The fossil representatives of the family Resinacaridae (Acari: Heterostigmata) from the Late Eocene Rovno amber are reviewed. Three new species are described in the genus Resinacarus Vitzthum, namely, R. longipilis sp. nov., R. vitzthumi sp. nov., and R. striatus sp. nov. A new genus and species, Pararesinacarus krczali gen. and sp. nov. are also described. The extant species Pararesinacarus aradii (Krczal) comb. nov. was moved from Resinacarus. All active stages of the extant type species of the genus Resinacarus, R. resinatus Vitzthum, are redescribed based on type material. A key to genera and species of Resinacaridae is also provided.

Basilobelba werneri (Oribatida, Basilobelbidae) was collected from an alpine cloud forest in Guatemala. This is the first representative of the family Basilobelbidae in the Guatemalan fauna. A supplementary description of adult B. werneri is presented along with summarized diagnostic morphological traits. The juvenile instars of B. werneri are described for the first time. The larva is characterized by the presence of 11 pairs of gastronotic setae, of which c1 (short), da and dm (medium-sized) slightly thickened, barbed, la, lm, lp, h1, and h2 long, thick, narrowed distally, heavily barbed, and c2, c3 and h3 short, setiform, roughened. The proto-, deuto- and tritonymph are characterized by the presence of 12 pairs of short, setiform gastronotic setae.

The female of a new fossil genus and species, Rhombometridium pankowskiorum gen. and sp. nov. (Acari: Trochometridiidae), is described from Cretaceous Kachin amber. The new genus is characterized by the presence of well-developed sporothecae anteriad legs III, each sporotheca containing several ovoid fungal spores. This is the oldest (ca. 100 Mya), evidence of symbiosis between mites and fungi and the first fossil record of the mite family Trochometridiidae. The new genus shares synapomorphies with the family Trochometridiidae (presence of sporothecae between bases of legs III and IV) and Caraboacaridae (rhombic body shape, absence of setae v2, absence of palpal solenidion, palps fused with distinctly widened gnathosomal capsule), and potentially represents a transitional form or a missing link between these two closely related families. We also compare the sporothecae of R. pankowskiorum with those of other heterostigmatic mites.

A new monotypic fossil family Unguicheylidae fam. nov. with type genus and species Unguicheylus quadriocellatus gen. nov., sp. nov. is described from the early-Cretaceous (Albian–lower Cenomanian) amber of northern Siberia (Taimyr amber, Baikura locality). The new family is provisionally placed in the superfamily Anystoidea and most similar to the family Pseudocheylidae, but differs mainly in having apomorphically adnate cheliceral bases (free, mobile bases in Pseudocheylidae), and the tarsi of all legs lacking annulated pretarsal stalks bearing reduced claws (present, apomorphic to Pseudocheylidae).

The first record is presented of the sejoid genus Uropodella (family Uropodellidae, suborder Sejida) from Baltic amber, based on a well-preserved adult male. Morphologically, the specimen is as modern in structure as adults of the six known extant species of Uropodella. The diagnosis of the fossil in distinction to the extant species justifies naming it as a new species. This record traces the genus back to the Eocene, representing the oldest validated age for a mesostigmatan genus. A key to species of the genus Uropodella is given.

The systematic position of the subgenus Endopodalius Christian and Karg, 2006, previously recognized by Lindquist and Evans, 1965, as the scutalis species group in Lasioseius, is reviewed. Based in part on plesiomorphic structures of the female sperm access system being of a laelapoid type, it is removed as a subgenus of the blattisociid genus Lasioseius in the superfamily Phytoseioidea and accomodated as a separate genus within the superfamily Ascoidea. In other respects, adult females of this taxon are so distinctive apomorphically to justify separate family group recognition, Endopodaliidae, fam. nov., tentatively related as a sister-group to the morphologically and behaviorally more derived Antennochelidae Lindquist and Moraza, 2014. Species of this family are tropical, their adult females phoretic on beetles of various families of the infraorder Cucujiformia, suborder Polyphaga. A diagnosis of the family and revised description of Endopodalius based on adult females and males are presented, with an updated key to world recognized species of the genus, including the following new binominal combinations, Endopodalius americanus (Chant,1963), Endopodalius mouchei (Loots, 1980), and a new synonym: E. scutalis (Banks, 1914) (= E. prorsoperitrematus Abo-Shnaf et al., 2016). A lectotype is designated from type material of Hypoaspis scutalis Banks, 1914.

A new genus and species, Tarsobisulcus angulomarginis n. gen., n. sp. (Acari: Tarsonemidae: Pseudotaesonemoidini) is described based on females collected on larvae of the ga ll midge Xylodiplosis nigritarsis Zett. (Diptera: Cecidomyiidae) in oak wood from Norway. Some aspects of the morphology, systematic relationships and biology of Tarsobisulcus angulomarginis n. gen., n. sp. are discussed.

Determining the chelicerate tree of life has been the subject of much research, with deep phylogenetic divergences and high evolutionary rates complicating both morphological and molecular approaches (Noah et al., 2020; Ontano et al., 2021; Sharma et al., 2021; Ballesteros et al., 2022). Within Acari, similar challenges exist—even the basic question of whether Acari is mono- or diphyletic remains unresolved (Pepato & Klimov, 2015; Lozano-Fernandez et al., 2019; Van Dam et al., 2019; Ontano et al., 2021). Several recent molecular studies have attempted to resolve these issues using large multi-gene datasets (Pepato et al., 2022; Klimov et al., 2018), mitochondrial genomes (Ban et al., 2022), and transcriptomes (Lozano-Fernandez et al., 2019). Ultraconserved elements (Faircloth et al., 2012) have recently shown great promise for constructing phylogenies for both deeply- and shallowly-diverged taxa (Zhang et al., 2019), including for Chelicerata (Starrett et al., 2017) and for Arrenuridae within Acari (Shoop, 2019), but have not yet been used across the Acari.

The present article represents the first part of a review of fossil heterostigmatic mites collected from late Eocene Rovno amber. Here, mites of the families Tarsocheylidae, Dolichocybidae, and Acarophenacidae are described, with Tarsocheylidae and Dolichocybidae recorded for the first time from amber. A new genus and four new species are described, namely, Hoplocheylus similis sp. nov. (Tarsocheylidae), Dolichocybe elongata sp. nov. (Dolichocybidae), Proadactylidium fossibilis gen. and sp. nov. and Paradactylidium sineunguis sp. nov. (Acarophenacidae). The extant species Acarophenax lacunatus Cross and Krantz, 1964 and A. assanovi Livshitz and Mitrofanov, 1974 are transferred to the new genus Proadactylidium. A revised key to the genera of Acarophenacidae is presented. The homologies of prodorsal setae in Acarophenacidae are reconsidered and reviewed.

Iphidonopsis sculptus Gwiazdowicz, 2004, is currently known only from the type locality in eastern Poland and a record in southwestern Finland (Huhta, 2016). Here, we record this species from twelve localities elsewhere (Europe, Siberia, Far East of Russia, Canada) indicating its broadly Holarctic geographical range. Another genus member, Iphidonopsis magnanalis (Ma & Yin, 1999), is known only from China. About half of Iphidonopsis sculptus records are associated with litter of coniferous or mixed forests, but the others, including samples with juveniles (deutonymphs), were found in bracket fungi or under tree bark. The finding of two adult females on a bark beetle, Dryocoetes affaber (Mannerheim) (Coleoptera: Curculionidae: Scolytinae), suggests a phoretic association, though members of the closely related genus Zerconopsis Hull, 1918 as well as of all of the subfamily Arctoseiinae are known only from phoretic dispersal by nematoceran dipterans. The morphology of adults and an immature instar (deutonymph) of I. sculptus is redescribed and newly described, respectively, and illustrated in detail. A subdivision of the subfamily Arctoseiinae Evans, 1963 into three tribes is proposed—Arctoseiini Evans, 1963 (including Arctoseius Thor, 1930 and Iphidozercon Berlese, 1903), Zerconopsini tribe n. (Zerconopsis Hull, 1918; Xenoseius Lindquist & Evans, 1965; and Iphidonopsis Gwiazdowicz, 2004), and Maxiniini tribe n. (Maxinia Lindquist & Makarova, 2012).

The gamasine genus Berlesia Canestrini, 1884, is revived and further diagnosed, based on descriptions of adult females, males and nymphs of three new species (B. hospitabilis sp. nov., B. multisetosa sp. nov., B. vorontsovi sp. nov.) ectoparasitic on raspy crickets of three genera of Gryllacrididae (Ensifera) from Australia and the Philippines. A tight sister relationship of Berlesia with the monobasic genus Katydiseius Fain & Lukoschus, 1983, known only from a pseudophylline katydid in Malaysia, is proposed. The subfamily Katydiseiinae Fain & Lukoschus, 1983 (previously included in the family Otopheidomenidae in the superfamily Phytoseioidea) is redefined to include only those two genera, and moved to the dermanyssoid family Laelapidae, while its previously other monobasic genus, Eickwortius Zhang, 1995, is retained tentatively in the family Otopheidomenidae. Among other taxa relevant to Katydiseiinae reviewed here, Berlesia cultrigera Berlese, 1910a is transferred to the genus Orthopteroseius Mo, 1996, at present Otopheidomenidae, as Orthopteroseius cultrigerum (Berlese) comb. nov., and Berlesia nuda Berlese, 1910b is transferred to the genus Prasadiseius Wainstein, 1972, at present Otopheidomenidae, as Prasadiseius nudum (Berlese) comb. nov. A key to the two genera and five species recognized as belonging in Katydiseiinae is presented. Notable morphological traits of Berlesia, including only deutonymphs equipped with well-developed claws and males with dimorphically more elongated salivary stylets, are discussed. The one known life cycle of a species of Berlesia, B. hospitabilis sp. nov., includes protonymphipary, followed by a fully functioning deutonymph, and male copulation with pharate females—traits, rarely or not known among gamasine mite associates of invertebrates. The possible significance of elongate spermatodactyls and male reduced feeding are explored.

Summaries of taxonomic knowledge are provided for all acarine groups in Canada, accompanied by references to relevant publications, changes in classification at the family level since 1979, and notes on biology relevant to estimating their diversity. Nearly 3000 described species from 269 families are recorded in the country, representing a 56% increase from the 1917 species reported by Lindquist et al. (1979). An additional 42 families are known from Canada only from material identified to family- or genus-level. Of the total 311 families known in Canada, 69 are newly recorded since 1979, excluding apparent new records due solely to classification changes. This substantial progress is most evident in Oribatida and Hydrachnidia, for which many regional checklists and family-level revisions have been published. Except for recent taxonomic leaps in a few other groups, particularly of symbiotic mites (Astigmata: feather mites; Mesostigmata: Rhinonyssidae), knowledge remains limited for most other taxa, for which most species records are unpublished and may require verification. Taxonomic revisions are greatly needed for a large majority of families in Canada. Based in part on species recorded in adjacent areas of the USA and on hosts known to be present here, we conservatively estimate that nearly 10,000 species of mites occur in Canada, but the actual number could be 15,000 or more. This means that at least 70% of Canada’s mite fauna is yet unrecorded. Much work also remains to match existing molecular data with species names, as less than 10% of the ~7500 Barcode Index Numbers for Canadian mites in the Barcode of Life Database are associated with named species. Understudied hosts and terrestrial and aquatic habitats require investigation across Canada to uncover new species and to clarify geographic and ecological distributions of known species.

Adult females of a new species, Mucroseius insolitus sp. nov., are described from the metathoracic spiracular atria of the Black pine sawyer beetle Monochamus galloprovincialis (Coleoptera: Cerambycidae) from Asian Russia (Altai Republic and Tyumen Province). The new species differs from all congeners by the absence of the otherwise autapomorphic distal flangelike process (mucro) of the fixed chela. The genus Mucroseius is recorded for the first time in Russia, and its generic concept is reviewed.urn:lsid:zoobank.org:act:AB3BDB6A-63C3-4970-A192-A3C539C48BA1

A new species of the ectoparasitic mite genus Podapolipus Rovelli & Grassi, 1888 from a recently described species of the raspy cricket genus Chauliogryllacris Rentz, in Rentz and John,1990 (Orthoptera: Gryllacrididae) is described. The main distinctions of Podapolipus gryllacridi n. sp. from its described congeners from orthopterans are the larval female and adult male having all dorsal and ventral idiosomatic setae, except the greatly elongated pair of scapular setae (and the caudal setae of the larval female), reduced to the size of microsetae; the larval female having separate tergites C and D; the male having an entire prodorsal shield, with apex of the aedeagus between bases of setae v1; and the adult female having smooth dorsal shields. Novel biological features of this parasite include its adult females’ dwelling in the hollow sternal apodemes of their host, and its larval females using their host’s other parasite, a gamasine mite, as phoretic and facultative hyperparasitic hosts. Keys are presented for the larval females and adult males of Podapolipus species associated with orthopterans. Problems with the generic concept of Podapolipus and closely related genera are reviewed. This is the first record of a podapolipid associated with orthopterans of the family Gryllacrididae.

The genus Leioseius Berlese is reviewed, faunistically in North America, and taxonomically, world-wide. Descriptions of two new species, redescriptions of two previously recorded species, and first records of Leioseius elongatus Evans in North America are presented. Observations indicate that various leg setal and pretarsal attributes are useful in taxonomic discrimination of species in this genus. A key to North American species based on both idiosomatic and leg setal aspects is presented. Four species previously described under the genus Iphidozercon Berlese are accounted for the first time as species of Leioseius, and other taxa described previously as four yet other species of Leioseius are transferred to other genera. A tentative key, provided for separation of females of the 22 recognizable world Leioseius species, accounts for these changes. General morphological notes about mites of this genus are presented, some of which may lead to recognition of species-groups. Scant, general biological aspects about Leioseius mites are presented.

A new species-group of Lasioseius is described from adults and immatures of four newly described and one undescribed species associated with hispine beetles of the genera Cephaloleia and Chelobasis and other gamasine mites in the furled leaf habitat of Heliconia and related Zingiberales plants. The species-group presents a suite of apomorphic attributes placing it in the subgenus L. (Lasioseius). Adults and immatures were found moving freely on and off the beetles when the latter were exposed from their habitat. Larviparity is indicated by adult females gravid with fully developed larvae. Limited data suggest considerable host specificity between mites and their beetle hosts, indicating that there may be a vast diversity of these mites associated with hundreds of species of hispine beetles in the Neotropical Region. Keys are provided to currently accepted species-groups of Lasioseius and to the species within the new species-group.