Showing papers by "Rolf G. Beutel published in 2022"

Permian parallelisms: Reanalysis of †Tshekardocoleidae sheds light on the earliest evolution of the Coleoptera

Abstract: The Coleoptera provides an excellent example of the value of fossils for understanding the evolutionary patterns of recent lineages. We reevaluate the morphology of the Early Permian †Tshekardocoleidae to test alternative phylogenetic hypotheses relating to the Palaeozoic evolution of the order. We discuss prior interpretations and revise an earlier data matrix. Both Bayesian and parsimony analyses support the monophyly of Coleoptera excluding †Tshekardocoleidae (= Mesocoleoptera), and of Coleoptera excluding †Tshekardocoleidae and †Permocupedidae (= Metacoleoptera). Plesiomorphies preserved in †Tshekardocoleidae are elytra, which rest over the body in a loose tent‐like manner, with flat lateral flanges, projecting beyond the abdominal apex, and abdomens that are flexible and nearly cylindrical. Apomorphies of Mesocoleoptera include shortening of the elytra and a closer fit with the flattened and probably more rigid abdomen. A crucial synapomorphy of Metacoleoptera is the tightly sealed subelytral space, which may have been advantageous during the Permian aridification. Taxon exclusion experiments show that †Tshekardocoleidae is crucial for understanding the early evolution of Coleoptera and that its omission strongly affects ancestral state polarities as well as topology, including crown‐group taxa. By constraining the relationships of extant taxa to match those supported by phylogenomic analysis, we demonstrate that features shared by Archostemata with Permian stem groups are most reasonably supported as plesiomorphic and that the smooth and simplified body forms of Polyphaga, Adephaga, Myxophaga, and Micromalthidae were derived in parallel. Our study highlights the reciprocal illumination of molecular, morphological, and paleontological data, and paves the way for tip‐dating analysis across the order.

The Skeletomuscular System of the Mesosoma of Formica rufa Workers (Hymenoptera: Formicidae)

Abstract: Abstract The mesosoma is the power core of the ant, containing critical structural and muscular elements for the movement of the head, legs, and metasoma. It has been hypothesized that adaptation to ground locomotion and the loss of flight led to the substantial rearrangements in the mesosoma in worker ants and that it is likely the ant mesosoma has undergone functional modifications as ants diversified into different ecological and behavioral niches. Despite this importance, studies on the anatomy of the ant mesosoma are still scarce, and there is limited understanding of important variation of internal structures across the ant phylogeny. Recent advances in imaging techniques have made it possible to digitally dissect small insects, to document the anatomy efficiently and in detail, and to visualize these data in 3D. Here we document the mesosomal skeletomuscular system of workers of the red wood ant, Formica rufa Linnaeus, 1761, and use it to establish a 3D atlas of mesosomal anatomy that will serve as reference work for further studies. We discuss and illustrate the configuration of the skeletomuscular components and the function of the muscles in interaction with the skeletal elements. This anatomical evaluation of a ‘generalized’ ant provides a template for future studies of the mesosoma across the radiation of Formicidae, with the ultimate objective of synthesizing structural, functional, and transformational information to understand the evolution of a crucial body region of ants.

Evidence for the evolution of eusociality in stem ants and a systematic revision of † Gerontoformica (Hymenoptera: Formicidae)

Abstract: It is generally assumed that Cretaceous stem ants were obligately eusocial, because of the presence of wingless adult females, yet the available evidence is ambiguous. Here, we report the syninclusion of a pupa and adult of a stem ant species from Mid-Cretaceous amber. As brood are immobile, the pupa was likely to have been transported by an adult. Therefore, the fossil substantiates the hypothesis that wingless females were cooperators, thus these were true ‘workers’. Re-examination of all described Cretaceous ant species reveals that winged–wingless diphenism – hence a variable dispersal capacity – may have been ancestral to the total clade of the ants, and that highly specialized worker-specific phenotypes evolved in parallel between the stem and crown groups. The soft-tissue preservation of the fossil is exceptional, demonstrating the possibility of analysing the development of the internal anatomy in stem ants. Based on the highest-resolution µ-CT scans of stem ants to date, we describe † Gerontoformica sternorhabda sp. nov. , redescribe † G. gracilis , redefine the species group classification of † Gerontoformica , and provide a key to the species of the genus. Our work clarifies the species boundaries of † Gerontoformica and renders fossils relevant to the discussion of eusocial evolution in a way that has heretofore been intractable.

The First Reconstruction of the Head Anatomy of a Cretaceous Insect, †Gerontoformica gracilis (Hymenoptera: Formicidae), and the Early Evolution of Ants

Abstract: Abstract The fossil record allows a unique glimpse into the evolutionary history of organisms living on Earth today. We discovered a specimen of the stem group ant †Gerontoformica gracilis (Barden and Grimaldi, 2014) in Kachin amber with near-complete preservation of internal head structures, which we document employing µ-computed-tomography-based 3D reconstructions. We compare †Gerontoformica to four outgroup taxa and four extant ant species, employing parsimony and Bayesian ancestral state reconstruction to identify morphological differences and similarities between stem and crown ants and thus improve our understanding of ant evolution through the lens of head anatomy. Of 149 morphological characters, 87 are new in this study, and almost all applicable to the fossil. †Gerontoformica gracilis shares shortened dorsal tentorial arms, basally angled pedicels, and the pharyngeal gland as apomorphies with other total clade Formicidae. Retained plesiomorphies include mandible shape and features of the prepharynx. Implications of the reconstructed transitions especially for the ant groundplan are critically discussed based on our restricted taxon sampling, emphasizing the crucial information derived from internal anatomy which is applied to deep time for the first time. Based on the falcate mandible in †Gerontoformica and other Aculeata, we present hypotheses for how the shovel-shaped mandibles in crown Formicidae could have evolved. Our results support the notion of †Gerontoformica as ‘generalized’ above-ground predator missing crucial novelties of crown ants which may have helped the latter survive the end-Cretaceous extinction. Our study is an important step for anatomical research on Cretaceous insects and a glimpse into the early evolution of ant heads. Graphical Abstract

Phylogenetic Revision and Patterns of Host Specificity in the Fungal Subphylum Entomophthoromycotina

Abstract: The Entomophthoromycotina, a subphylum close to the root of terrestrial fungi with a bias toward insects as their primary hosts, has been notoriously difficult to categorize taxonomically for decades. Here, we reassess the phylogeny of this group based on conserved genes encoding ribosomal RNA and RNA polymerase II subunits, confirming their general monophyly, but challenging previously assumed taxonomic relationships within and between particular clades. Furthermore, for the prominent, partially human-pathogenic taxon Conidiobolus, a new type species C. coronatus is proposed in order to compensate for the unclear, presumably lost previous type species C. utriculosus Brefeld 1884. We also performed an exhaustive survey of the broad host spectrum of the Entomophthoromycotina, which is not restricted to insects alone, and investigated potential patterns of co-evolution across their megadiverse host range. Our results suggest multiple independent origins of parasitism within this subphylum and no apparent co-evolutionary events with any particular host lineage. However, Pterygota (i.e., winged insects) clearly constitute the most dominantly parasitized superordinate host group. This appears to be in accordance with an increased dispersal capacity mediated by the radiation of the Pterygota during insect evolution, which has likely greatly facilitated the spread, infection opportunities, and evolutionary divergence of the Entomophthoromycotina as well.

Phylogeny and systematics of Sphaeriusidae (Coleoptera: Myxophaga): minute living fossils with underestimated past and present‐day diversity

Abstract: Sphaeriusidae (Coleoptera: Myxophaga) is a group of shiny, blackish and hemispherical riparian beetles, known for their miniaturized bodies. They are worldwide in distribution, but very limited information is available about taxonomic and morphological diversity, and natural and evolutionary history. The aim of this study is to help fill in these gaps. We examined the external morphology of modern representatives using scanning electron microscopy (SEM), and reconstructed the phylogeny of the family using five DNA markers (cytochrome oxidase I, 18S rRNA, 28S rRNA, CAD and wingless). Our results suggest a larger morphological diversity than previously expected, corresponding to the deep genetic divergences of principal lineages. We also examined two inclusions in 99‐million‐year‐old Burmese amber. The integration of all evidence allows us to recognize three genera: the extinct genus †Burmasporum Kirejtshuk, the newly defined genus Bezesporum gen.nov. preserved in Burmese amber (B. burmiticum sp.nov.) and present in the modern fauna of Southeast Asia, and the genus Sphaerius Waltl with a world‐wide distribution. Sphaerius species are morphologically highly uniform, with the exception of species from Australia and South Africa, which share some characteristics with Bezesporum gen.nov. despite being resolved as deeply nested lineages of Sphaerius by DNA data. The presence of Bezesporum gen.nov. in Burmese amber and in recent fauna indicates that Sphaeriusidae largely maintained their specific morphology and specialized riparian lifestyle for at least 100 million years. Therefore, they can be considered an exceptionally conserved group, with a minimum of evolutionary changes over a long period. Our study also demonstrates that the species numbers and fine‐scale morphological diversity of Sphaeriusidae are larger than expected in both the past and present‐day faunas. Both were apparently underestimated due to the minute body size and cryptic habits of these beetles.

Rapid and Selective Absorption of Plant Defense Compounds From the Gut of a Sequestering Insect

Abstract: Many herbivorous insects exploit defense compounds produced by their host plants for protection against predators. Ingested plant defense compounds are absorbed via the gut epithelium and stored in the body, a physiological process that is currently not well understood. Here, we investigated the absorption of plant defense compounds from the gut in the horseradish flea beetle, Phyllotreta armoraciae, a specialist herbivore known to selectively sequester glucosinolates from its brassicaceous host plants. Feeding experiments using a mixture of glucosinolates and other glucosides not found in the host plants showed a rapid and selective uptake of glucosinolates in adult beetles. In addition, we provide evidence that this uptake mainly takes place in the foregut, whereas the endodermal midgut is the normal region of absorption. Absorption via the foregut epithelium is surprising as the apical membrane is covered by a chitinous intima. However, we could show that this cuticular layer differs in its structure and overall thickness between P. armoraciae and a non-sequestering leaf beetle. In P. armoraciae, we observed a thinner cuticle with a less dense chitinous matrix, which might facilitate glucosinolate absorption. Our results show that a selective and rapid uptake of glucosinolates from the anterior region of the gut contributes to the selective sequestration of glucosinolates in P. armoraciae.

The earliest beetle †Coleopsis archaica (Insecta: Coleo­ptera) – morphological re-evaluation using Reflectance Transformation Imaging (RTI) and phylogenetic assessment

Abstract: The earliest know n fossil beetle †Coleopsis archaica is re-examined using Reflectance Transformation Imaging (RTI). The morphological observations are evaluated with respect to phylogenetic implications and the early evolution of Coleoptera. †Coleopsis archaica belongs to an early Permian branch of beetles, outside a monophyletic unit comprising Coleoptera (in the widest sense) excluding †Tshekardocoleidae. This clade is mainly characterized by a complex of apomorphic features: elytra with epipleura and with a close fit with the posterior body, thus forming a tightly sealed subelytral space. In contrast to this, the elytra of †C. archaica and †Tshekardocoleidae cover the metathorax and abdomen in a loose tent-like manner and posteriorly distinctly surpass the abdominal apex. So far, no synapomorphies of the two taxa from the first half of the Permian have been identified. The very short and transverse pronotum is likely an autapomorphy of †C. archaica. A thorough documentation of the structural features of early beetle fossils should have high priority. RTI is a very promising tool to obtain new and well-founded morphological data, which will allow a thorough phylogenetic evaluation of Permian beetles in future studies. We extended the conventional RTI workflow by focus merging and panoramic stitching, in order to overcome previous limitations. Taxonomic re-arrangements of stem group beetles including †C. archaica were suggested in recent studies by A.G. Kirejtshuk and co-workers. As they are not based on shared derived features they are irrelevant in a phylogenetic and evolutionary context.

A generic classification of Xenidae (Strepsiptera) based on the morphology of the female cephalothorax and male cephalotheca with a preliminary checklist of species

Abstract: Abstract The generic taxonomy and host specialization of Xenidae have been understood differently by previous authors. Although the recent generic classification has implied a specialization on the level of host families or subfamilies, the hypothesis that each xenid genus is specialized to a single host genus was also previously postulated. A critical evaluation of the classification of the genera of Xenidae is provided here based on morphology in accordance with results of recent molecular phylogenetic studies. External features of the female cephalothoraces and male cephalothecae were documented in detail with different techniques. Diagnoses and descriptions are presented for all 13 delimited genera. The earliest diverging genera are usually well characterized by unique features, whereas deeply nested genera are usually characterized by combinations of characters. Three new genera are described: Sphecixenosgen. nov., Tuberoxenosgen. nov., and Deltoxenosgen. nov. Five previously described genera are removed from synonymy: Tachytixenos Pierce, 1911, stat. res.; Brasixenos Kogan & Oliveira, 1966, stat. res.; Leionotoxenos Pierce, 1909, stat. res.; Eupathocera Pierce, 1908, stat. res.; and Macroxenos Schultze, 1925, stat. res. One former subgenus is elevated to generic rank: Nipponoxenos Kifune & Maeta, 1975, stat. res.Monobiaphila Pierce, 1909, syn. nov. and Montezumiaphila Brèthes, 1923, syn. nov. are recognized as junior synonyms of Leionotoxenos Pierce, 1909, stat. res.Ophthalmochlus Pierce, 1908, syn. nov., Homilops Pierce, 1908, syn. nov., Sceliphronechthrus Pierce, 1909, syn. nov., and Ophthalmochlus (Isodontiphila) Pierce, 1919, syn. nov. are recognized as junior synonyms of Eupathocera Pierce, 1908, stat. res. A preliminary checklist of 119 described species of Xenidae with information on their hosts and distribution is provided. The following 14 species are recognized as valid and restituted from synonymy: Tachytixenosindicus Pierce, 1911, stat. res.; Brasixenosacinctus Kogan & Oliveira, 1966, stat. res.; Brasixenosaraujoi (Oliveira & Kogan, 1962), stat. res.; Brasixenosbahiensis Kogan & Oliveira, 1966, stat. res.; Brasixenosbrasiliensis Kogan & Oliveira, 1966, stat. res.; Brasixenosfluminensis Kogan & Oliveria, 1966, stat. res.; Brasixenosmyrapetrus Trois, 1988, stat. res.; Brasixenoszikani Kogan & Oliveira, 1966, stat. res.; Leionotoxenoshookeri Pierce, 1909, stat. res.; Leionotoxenosjonesi Pierce, 1909, stat. res.; Leionotoxenoslouisianae Pierce, 1909, stat. res.; Eupathoceraluctuosae Pierce, 1911, stat. res.; Eupathoceralugubris Pierce, 1909, stat. res.; Macroxenospiercei Schultze, 1925, stat. res. New generic combinations are proposed for 51 species: Leionotoxenosarvensidis (Pierce, 1911), comb. nov.; Leionotoxenosbishoppi (Pierce, 1909), comb. nov.; Leionotoxenosforaminati (Pierce, 1911), comb. nov.; Leionotoxenosfundati (Pierce, 1911), comb. nov.; Leionotoxenoshuastecae (Székessy, 1965), comb. nov.; Leionotoxenositatiaiae (Trois, 1984), comb. nov.; Leionotoxenosneomexicanus (Pierce, 1919), comb. nov.; Leionotoxenosprolificum (Teson & Remes Lenicov, 1979), comb. nov.; Leionotoxenosrobertsoni (Pierce, 1911), comb. nov.; Leionotoxenostigridis (Pierce, 1911), comb. nov.; Leionotoxenosvigili (Brèthes, 1923), comb. nov.; Eupathoceraargentina (Brèthes, 1923), comb. nov.; Eupathoceraauripedis (Pierce, 1911), comb. nov.; Eupathocerabucki (Trois, 1984), comb. nov.; Eupathoceraduryi (Pierce, 1909), comb. nov.; Eupathoceraerynnidis (Pierce, 1911), comb. nov.; Eupathocerafasciati (Pierce, 1909), comb. nov.; Eupathocerafuliginosi (Brèthes, 1923), comb. nov.; Eupathocerainclusa (Oliveira & Kogan, 1963), comb. nov.; Eupathocerainsularis (Kifune, 1983), comb. nov.; Eupathoceramendozae (Brèthes, 1923), comb. nov.; Eupathocerapiercei (Brèthes, 1923), comb. nov.; Eupathocerastriati (Brèthes, 1923), comb. nov.; Eupathocerataschenbergi (Brèthes, 1923), comb. nov.; Eupathocerawestwoodii (Templeton, 1841), comb. nov.; Macroxenospapuanus (Székessy, 1956), comb. nov.; Sphecixenosabbotti (Pierce, 1909), comb. nov.; Sphecixenosastrolabensis (Székessy, 1956), comb. nov.; Sphecixenosdorae (Luna de Carvalho, 1956), comb. nov.; Sphecixenoserimae (Székessy, 1956), comb. nov.; Sphecixenosesakii (Hirashima & Kifune, 1962), comb. nov.; Sphecixenosgigas (Pasteels, 1950), comb. nov.; Sphecixenoskurosawai (Kifune, 1984), comb. nov.; Sphecixenoslaetum (Ogloblin, 1926), comb. nov.; Sphecixenosorientalis (Kifune, 1985), comb. nov.; Sphecixenosreticulatus (Luna de Carvalho, 1972), comb. nov.; Sphecixenossimplex (Székessy, 1956), comb. nov.; Sphecixenosvanderiisti (Pasteels, 1952), comb. nov.; Tuberoxenosaltozambeziensis (Luna de Carvalho, 1959), comb. nov.; Tuberoxenossinuatus (Pasteels, 1956), comb. nov.; Tuberoxenossphecidarum (Siebold, 1839), comb. nov.; Tuberoxenosteres (Pasteels, 1950), comb. nov.; Tuberoxenostibetanus (Yang, 1981), comb. nov.; Deltoxenosbequaerti (Luna de Carvalho, 1956), comb. nov.; Deltoxenosbidentatus (Pasteels, 1950), comb. nov.; Deltoxenoshirokoae (Kifune & Yamane, 1992), comb. nov.; Deltoxenosiwatai (Esaki, 1931), comb. nov.; Deltoxenoslusitanicus (Luna de Carvalho, 1960), comb. nov.; Deltoxenosminor (Kifune & Maeta, 1978), comb. nov.; Deltoxenosrueppelli (Kinzelbach, 1971a), comb. nov.; Xenosropalidiae (Kinzelbach, 1975), comb. nov.Xenosminor Kinzelbach, 1971a, syn. nov. is recognized as a junior synonym of X.vesparum Rossi, 1793. Ophthalmochlusduryi Pierce, 1908, nomen nudum and Eupathoceralugubris Pierce, 1908, nomen nudum are recognized as nomina nuda and therefore unavailable in zoological nomenclature. The species diversity of Xenidae probably remains poorly known: the expected number of species is at least twice as high as the number presently described.

Unearthing underground predators: The head morphology of larvae of the moth lacewing genus Ithone Newman (Neuroptera: Ithonidae) and its functional and phylogenetic implications

Abstract: Moth lacewings (Ithonidae) are a rare group of Neuroptera with an unusual subterranean larval life‐style. We examined external and internal head structures of an older‐instar larva of Ithone Newman with a broad spectrum of techniques. Larval autapomorphies, likely correlated with the subterranean habits, are the compact and shovel‐shaped head, unusually massive mandibular‐maxillary stylets, and a C‐shaped postcephalic body. Other cephalic autapomorphies are the massive X‐shaped tentorium, incurved antennae, and a strongly developed M. verticopharyngalis. The visual organs are distinctly simplified but a single functional stemma on each side of head is retained despite of the subterranean habits. In contrast to previous studies, a well‐developed gular sclerite is present in Ithonidae, possibly a secondary acquisition. A cephalic gland complex and poison channel are present, with an unexpected additional lateral accessory gland and an additional lateral channel. The poison glands and dual channels very clearly indicate that the larvae are predators, contradicting the phytophagous habits formerly postulated. Compared with soil‐inhabiting scarabaeoid beetle larvae, striking differences of head structures are due to different feeding habits and phylogenetic constraints. Morphological similarities like a C‐shaped postcephalic body and strongly developed legs suitable for burrowing in soil are evolutionary parallels associated with the subterranean life‐style in the two non‐related groups. Bayesian phylogenetic analysis was carried out with an updated morphological matrix. The results were compared with a phylogeny based on anchored hybrid enrichment data. The evolutionary transformations of selected characters were evaluated using phylogenies estimated from both datasets.

Correction: Comparative dissection of the peripheral olfactory system of the Chagas disease vectors Rhodnius prolixus and Rhodnius brethesi

Abstract: [This corrects the article DOI: 10.1371/journal.pntd.0009098.].

Systematic Position of Ptilophorus dufourii Inferred from Its Primary Larva, with Notes on Ptilophorinae (Coleoptera: Ripiphoridae)

Abstract: Abstract. Since the description of Ptilophorus dufourii (Latreille, 1818), the unknown immature stages and biology of Ptilophorinae is one of the longest persisting gap in the research of the wedge-shaped beetles (Ripiphoridae). Here we describe the primary larva of P. dufourii based on SEM and CLSM images. Its modified mouthparts unsuitable to grasp prey rule out predaceous habits and also processing any solid substrates (e.g., wood or other fresh plant tissues). In contrast, the weakly sclerotized and very small body, the enlargement of the sensorial appendage of the antennae, and simplified mouthparts strongly suggest parasitism and consumption of liquid food. We provide a comparison with the only known larva of Pelecotominae, another possible basal lineage of Ripiphoridae, and discuss potential synapomorphies and differences between larvae of both subfamilies. A sistergroup relationship between Ptilophorinae and Pelecotominae is suggested by the presence of only two stemmata, spatulate femoral setae, a scale-like lateral cranial surface, and an enlarged antennal sensorial appendage, and a clade Ripidiini + Ripiphorinae by a characteristic boat-shape of the primary larvae. The host of P. dufourii remains unknown. We reviewed published host records, but none of them is based on traceable evidence and none of them appears credible. Observations of adult behaviour of P. dufourii are documented. Taxonomy and systematics of Ptilophorus and Ptilophorinae are discussed. The Cretaceous Spinotoma ruicheni Hsiao et Huang, 2017 is transferred from Pelecotominae to Ptilophorinae in accordance with diagnostic characters given in the original description and current definitions of both subfamilies.

Have female twisted-wing parasites (Insecta: Strepsiptera) evolved tolerance traits as response to traumatic penetration?

Abstract: Traumatic insemination describes an unusual form of mating during which a male penetrates the body wall of its female partner to inject sperm. Females unable to prevent traumatic insemination have been predicted to develop either traits of tolerance or of resistance, both reducing the fitness costs associated with the male-inflicted injury. The evolution of tolerance traits has previously been suggested for the bed bug. Here we present data suggesting that tolerance traits also evolved in females of the twisted-wing parasite species Stylops ovinae and Xenos vesparum. Using micro-indentation experiments and confocal laser scanning microscopy, we found that females of both investigated species possess a uniform resilin-rich integument that is notably thicker at penetration sites than at control sites. As the thickened cuticle does not seem to hamper penetration by males, we hypothesise that thickening of the cuticle resulted in reduced penetration damage and loss of haemolymph and in improved wound sealing. To evaluate the evolutionary relevance of the Stylops-specific paragenital organ and penis shape variation in the context of inter- and intraspecific competition, we conducted attraction and interspecific mating experiments, as well as a geometric-morphometric analysis of S. ovinae and X. vesparum penises. We found that S. ovinae females indeed attract sympatrically distributed congeneric males. However, only conspecific males were able to mate. In contrast, we did not observe any heterospecific male attraction by Xenos females. We therefore hypothesise that the paragenital organ in the genus Stylops represents a prezygotic mating barrier that prevents heterospecific matings.

A unique case of commensalism: The beaver beetle Platypsyllus castoris (Leiodidae, Coleoptera) and its morphological adaptations

Abstract: Platypsyllus castoris is closely associated with beavers and displays a unique set of structural specializations. We document the morphology of adults with modern techniques, and interpret evolutionary changes linked with the specific life style. The small subfamily Platypsyllinae has evolved an entire suite of features correlated with a more or less close association with mammals, for instance a flattened body, a dorsal cephalic shield, flightlessness, eye reduction, and depigmentation. Within this small group, Platypsyllus displays numerous autapomorphic features, correlated with a close association with the beaver. Essential is a combination of mechanical stabilization and firm anchorage on the host, and efficient forward movement in the fur. Exo‐ and endoskeletal structures of the head and thorax are reinforced by vertical cuticular columns and by an array of internal ridges. The antennae are shortened and strongly modified, the mandibles distinctly reduced and flattened, unsuitable for cutting, scraping or grinding. The musculature of the mouthparts is simplified, whereas an enhanced set of prepharyngeal and pharyngeal dilators forms an efficient sucking pump. The prothoracic musculature is strongly developed. In contrast, the pterothoracic muscle system is distinctly simplified, even though leg muscles are strongly developed. Using the legs, the flattened beetles move sideways through the dense fur of the beaver, using posteriorly directed groups of setae and ctenidia to prevent being pushed backwards by the densely arranged hairs. In contrast to the anterior body, the cuticle of the abdomen is thin, and the entire tagma flexible, with thin layers of segmental muscles. The hind gut is not connected with the mid gut. The beetles probably consume liquid, possibly with emulgated minute skin debris. As the morphology of the mouthparts excludes damage to the skin of the host, the association should not be addressed as ectoparasitic but as commensalism.

The thoracic anatomy of Pselaphus heisei (Pselaphinae, Staphylinidae, Coleoptera)

Abstract: We document external and internal thoracic structures of the free‐living pselaphine beetle Pselaphus heisei (Pselaphitae) using a set of traditional and modern techniques. Like in the specialized myrmecophile Claviger testaceus (Clavigeritae), the skeletal elements of the pro‐ and pterothorax are highly compact, with largely reduced inter‐ and intrasegmental sutures. Features previously listed as synapomorphies of staphylinid subgroups, to which Pselaphinae belong, are confirmed for P. heisei. The only previously proposed thoracic synapomorphy of Pselaphinae, the mesoventral foveae, is likely transformed in P. heisei: we assume that the concavities are directed mesad and internally fused, thus forming a broad channel (“perforation”) extending through the keel‐like median region of the mesoventrite. The prothoracic foveal system is strongly reduced, with only one pair of pits present in front of the procoxae. Their internal invaginations form a transverse ventral endoskeletal bar that stabilizes the prothorax. The condition observed in the free‐living P. heisei is in contrast with previous hypotheses linking the reduction of the foveal system with myrmecophily. Moreover, traces of the mesoventral foveae are even preserved in the highly specialized inquiline C. testaceus. Gland cells are associated with areas of hyaline squamose setae on different body regions, suggesting release of secretions on the ventral side of the head, pro‐ and mesothorax, and abdominal base. Similar specialized setal patches are common in Pselaphini and related groups within Pselaphitae. The prothoracic musculature in P. heisei is more complex than that in the myrmecophilous C. testaceus and the free‐living, unspecialized Creophilus maxillosus (Staphylininae). The metathoracic muscle system is strongly simplified, demonstrating that P. heisei cannot fly, even though wings, some skeletal elements of the flight apparatus, and some small direct flight muscles are preserved. It cannot be fully excluded that indirect flight muscles and thus a functional flight apparatus is preserved in a certain percentage of individuals.

Two new species of Xenos (Strepsiptera: Xenidae), parasites of social wasps of the genus Mischocyttarus (Hymenoptera: Vespidae) in the New World

Abstract: Two new species of Strepsiptera of the genus Xenos Rossi, 1793 (Xenidae) from the New World are described. Both are endoparasites of social wasps of the genus Mischocyttarus Saussure, 1853 (Vespidae: Mischocyttarini). Xenos bicolor Benda & Straka, sp. nov., parasitizes Mischocyttarus navajo Bequaert, 1933, Mischocyttarus flavitarsis (Saussure, 1854), and Mischocyttarus pallidipectus (Smith, 1857), whereas Xenos pallens Benda & Straka, sp. nov., is a parasite of Mischocyttarus costaricensis Richards, 1945 (Vespidae: Polistinae: Mischocyttarini). Diagnoses and descriptions of female cephalothoraces are presented for all three species that parasitize species of Mischocyttarus. Diagnoses and descriptions of male cephalothecae are presented for Xenos bicolor sp. nov. and Xenos pallens sp. nov. Additionally, a key for Xenos species parasitic on Mischocyttarus is provided based on characters of the female cephalothorax and male cephalotheca. Identification of Xenos species based on external morphology is discussed.

Systematic bias and the phylogeny of Coleoptera—A response to Cai et al. (2022) following the responses to Cai et al. (2020)

Abstract: Systematic bias is one of the major phylogenetic issues arising over the last two decades. Using methods designed to reduce compositional and rate heterogeneity, hence systematic bias, Cai and co‐workers (2022) (= CEA22) reanalyzed the DNA sequence dataset for Coleoptera of Zhang et al. (2018) (= ZEA). CEA22 suggest that their phylogenetic results and major evolutionary hypotheses about the Coleoptera should be favoured over other recently published studies. Here, we discuss the methodology of CEA22 with particular attention to how their perfunctory reanalysis of ZEA obfuscates rather than illuminates beetle phylogeny. Similar to published rebuttals of an earlier study of theirs, we specifically find that many of their claims are misleading, unsupported, or false. Critically, CEA22 fail to establish the stated premise for their reanalysis. They fail to demonstrate how composition or rate heterogeneity supposedly impacted the phylogeny estimate of ZEA, let alone the results of other recent studies. Moreover, despite their claim of comprehensive sampling of Coleoptera, their dataset is neither the most diverse with respect to species and higher taxa included, nor anywhere near the largest in terms of sequence data and sampled loci. Although CEA22 does contribute additional fossils for calibration, those seeking the best available estimate for Coleoptera phylogeny and evolution based on molecular data are advised to look elsewhere.

Morphology of larvae and pupae of the genus Autocrates (Coleoptera: Trictenotomidae) and its phylogenetic implications

Abstract: The trictenotomid genus Autocrates Thomson, 1860 is remarkable for its large and robust adults, but its larval morphology and bionomics have been unknown over the last 160 years. Here, we describe and illustrate in detail the eggs, and also the first and last instar larva and the pupa of Autocrates maqueti Drumont, 2006, based on specimens reared from identified adults collected in South Korea. The first instar larva is very similar to the known trictenotomid larvae of the genus Trictenotoma Gray, 1832, sharing the following features: distinctly flattened and parallel-sided, well-sclerotized head and largely unpigmented postcephalic body, lyre-shaped frontal arms, very short coronal suture, five pairs of stemmata, asymmetrical and tridentate mandibles with mola, simple and apically upturned urogomphi, and absence of longitudinal ridges on the thorax and abdomen. Differences occur in the primary chaetotaxy. The last instar larva is almost identical with Trictenotoma in general appearance, but the longitudinal tergal ridges of Autocrates are much denser and more widely distributed than those of Trictenotoma. Our preliminary assessment of features of immature stages confirms a close relationship of Trictenotomidae with the “salpingid group”, i.e. Salpingidae, Boridae, Pyrochroidae and Pythidae. A sister group relationship with Pythidae is likely. The putative synapomorphy is the subdivision of the ventral element of tergites IX, even though this condition is not visible in the first instars of Autocrates, and quite indistinct (but recognizable) in the last larval stage. The complete mitochondrial genome of A. maqueti is provided. A preliminary phylogenetic analysis of trictenotomid species is presented using two mitochondrial genes (16S and COI). The morphology of eggs and biological information on feeding and oviposition behaviors are also provided with photographs of adults and eggs.