Synopsis of the Japanese species of Aleocharinae (Coleoptera: Staphylinidae), with review of the type specimens II. Genus Myllaena Erichson of tribe Myllaenini,with redescription of four Japanese species

Four Japanese species the rove beetle genus Myllaena are redescribed based on the type material. They are: M. japonica Sharp, 1888, M. lewisi Cameron, 1933, M. rufotestacea Cameron, 1933, and M. torrentum Cameron, 1933. Myllaena chinoculata Pace, 1998 described from China is synonymized with M. lewisi. All of these species are illustrated and mapped.

A second fossil species of the enigmatic rove beetle genus Charhyphus in Eocene Baltic amber, with implications on the morphology of the female genitalia (Coleoptera: Staphylinidae: Phloeocharinae)

ABSTRACT Phloeocharinae is a small and likely non-monophyletic subfamily of rove beetles. The enigmatic genus Charhyphus Sharp, 1887 has long been placed in Phloeocharinae, whereas recent studies have found it to be phylogenetically very distant from the core members of this subfamily, suggesting the possibility that it actually deserves its own separate subfamily status. So far, the sole definitive fossil record for Charhyphus is known based on a single male from Eocene Baltic amber as represented by †Charhyphus balticus Shavrin, 2020. Here, we describe and illustrate another new Charhyphus species, †Charhyphus serratus sp. nov. Yamamoto & Shavrin, from Baltic amber based on a well-preserved female fossil. Considering the general proportions of the body and the head, this new species is most similar to †C. balticus. The new species differs from all known species by the development of strong serration of the lateral edges of the pronotum and features of the shape of the apical margin of the mesoventrite. By using X-ray micro-computed tomography, we succeeded in visualising not only the general habitus but also each individual body part, recovering a previously undocumented sclerite on the female internal genital segments in the genus. Morphological features of extinct and extant species of Charhyphus are briefly discussed. Figures of all extant Charhyphus species and a key for the genus are also provided. Our study is important for considering possible higher palaeodiversity, more common occurrence, and palaeobiogeography of Charhyphus.

Redescription of the genus Megastilicus Casey (Staphylinidae, Paederinae) with the description of a new species

The myrmecophilous Paederinae rove beetle genus Megastilicus Casey, 1889 from North America is reviewed based on museum specimens. Prior to this study, the genus was monotypic with one species Megastilicus formicarius Casey, 1889 described. Here, we provide a redescription of the genus and the type species, designate a lectotype, and provide pictures of habitus and illustrations of the aedeagus and genital segments. Additionally, we describe a new species for the genus, Megastilicus iowaensis sp. nov., include an identification key to the two species and present the distribution map of both of them, including new state records. We discuss the assignment of the genus to the subtribe Stilicina based on morphological features.

A new ant-mimetic species of Metopiellus (Staphylinidae: Pselaphinae) from the Northern Colombian Amazon

The genus Metopiellus (Staphylinidae: Pselaphinae) is confirmed in Colombia. A  new ant-mimetic species of Metopiellus, Metopiellus guanano sp. nov. is described from northern Amazon. Major diagnostic characters and ecological data are given. A new symbiotic association (rove beetle and fungus-growing ants) is hypothesized for the genus Apterostigma (Formicidae: Myrmicinae) and recorded for the first time for the country.

Further evidence of Cretaceous termitophily: Description of new termite hosts of the trichopseniine Cretotrichopsenius (Coleoptera: Staphylinidae), with emendations to the classification of lower termites (Isoptera)

Termites (Isoptera) are among the most ecologically ubiquitous of terrestrial eusocial insects and provide an attractive environment for symbionts, which have evolved numerous times independently, and in lineages as diverse as millipedes and beetles. Previous studies reported the discovery of unequivocal termitophily in mid-Cretaceous amber from northern Myanmar, providing evidence that pushed the origin of termitophily back into the Mesozoic. Here we report the discovery of two more pieces of Cretaceous amber containing individuals of the trichopseniine rove beetle Cretotrichopsenius burmiticus Cai et al., 2017 (Staphylinidae: Aleocharinae: Trichopseniini) preserved together with their potential host termites, providing further evidence regarding the association between these two insect lineages. Two new termite species and genera are described as putative hosts for C. burmiticus: Arceotermes hospitis Engel & Jiang, gen. et sp. nov. and Tanytermitalis philetaerus Engel & Cai, gen. et sp. nov. Each is included in a new family, Arceotermitidae Engel, fam. nov. (type genus: Arceotermes Engel & Jiang, gen. nov.), and Tanytermitidae Engel, fam. nov. (type genus: Tanytermes Engel et al., 2007). In order to better characterize these two families the classification of lower Isoptera and clade Xylophagodea (= Cryptocercidae + Isoptera) is emended with the following new taxa: Idanotermitinae Engel, subfam. nov.; Melqartitermitidae Engel, fam. nov.; Mylacrotermitidae Engel, fam. nov.; Krishnatermitidae Engel, fam. nov.; Cosmotermitinae Engel, subfam. nov.; Hodotermopsinae Engel, subfam. nov.; Artisoptera Engel, minord. nov.; Cryptocercaptera Engel, infraord. nov. Lower termites were remarkably diverse during the mid-Cretaceous but declined in diversity considerably by the Palaeogene. The fossil rove beetle Cretotrichopsenius Cai et al., 2017 currently provides the earliest definitive evidence of termitophily and the complex association between rove beetles and termites.