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Although the knowledge of the skeletal morphology of bees has progressed enormously, a corresponding advance has not happened for the muscular system. Most of the knowledge about bee musculature was generated over 50 years ago, well before the digital revolution for anatomical imaging, including the application of microcomputed tomography. This technique, in particular, has made it possible to dissect small insects digitally, document anatomy efficiently and in detail, and visualize these data three dimensionally. In this study, we document the skeletomuscular system of a cuckoo bee, Thyreus albomaculatus and, with that, we provide a 3D atlas of bee skeletomuscular anatomy. The results obtained for Thyreus are compared with representatives of two other bee families (Andrenidae and Halictidae), to evaluate the generality of our morphological conclusions. Besides documenting 199 specific muscles in terms of origin, insertion, and structure, we update the interpretation of complex homologies in the maxillolabial complex of bee mouthparts. We also clarify the complicated 3D structure of the cephalic endoskeleton, identifying the tentorial, hypostomal, and postgenal structures and their connecting regions. We describe the anatomy of the medial elevator muscles of the head, precisely identifying their origins and insertions as well as their homologs in other groups of Hymenoptera. We reject the hypothesis that the synapomorphic propodeal triangle of Apoidea is homologous with the metapostnotum, and instead recognize that this is a modification of the third phragma. We recognize two previously undocumented metasomal muscle groups in bees, clarifying the serial skeletomusculature of the metasoma and revealing shortcomings of Snodgrass' "internal-external" terminological system for the abdomen. Finally, we elucidate the muscular structure of the sting apparatus, resolving previously unclear interpretations. The work conducted herein not only provides new insights into bee morphology but also represents a source for future phenomic research on Hymenoptera., (© 2024 The Author(s). Journal of Morphology published by Wiley Periodicals LLC.)

Polyandry, the practice of females mating with multiple males, is a strategy found in many insect groups. Whether it increases the likelihood of receiving beneficial genes from male partners and other potential benefits for females is controversial. Strepsiptera are generally considered monandrous, but in a few species females have been observed copulating serially with multiple males. Here we show that the offspring of a single female can have multiple fathers in two Strepsiptera species: Stylops ovinae (Stylopidae) and Xenos vesparum (Xenidae). We studied female polyandry in natural populations of these two species by analysis of polymorphic microsatellite loci. Our results showed that several fathers can be involved in both species, in some cases up to four. Mating experiments with S. ovinae have shown that the first male to mates with a given female contributes to a higher percentage of the offspring than subsequent males. In X. vesparum, however, we found no significant correlation between mating duration and offspring contribution. The prolonged copulation observed in S. ovinae may have the advantage of reducing competition with sperm from other males. Our results show that monandry may not be the general pattern of reproduction in the insect order Strepsiptera., (© 2024. The Author(s).)

The spectacular radiation of insects has produced a stunning diversity of phenotypes. During the past 250 years, research on insect systematics has generated hundreds of terms for naming and comparing them. In its current form, this terminological diversity is presented in natural language and lacks formalization, which prohibits computer-assisted comparison using semantic web technologies. Here we propose a Model for Describing Cuticular Anatomical Structures (MoDCAS) which incorporates structural properties and positional relationships for standardized, consistent, and reproducible descriptions of arthropod phenotypes. We applied the MoDCAS framework in creating the ontology for the Anatomy of the Insect Skeleto-Muscular system (AISM). The AISM is the first general insect ontology that aims to cover all taxa by providing generalized, fully logical, and queryable, definitions for each term. It was built using the Ontology Development Kit (ODK), which maximizes interoperability with Uberon (Uberon multispecies anatomy ontology) and other basic ontologies, enhancing the integration of insect anatomy into the broader biological sciences. A template system for adding new terms, extending, and linking the AISM to additional anatomical, phenotypic, genetic, and chemical ontologies is also introduced. The AISM is proposed as the backbone for taxon-specific insect ontologies and has potential applications spanning systematic biology and biodiversity informatics, allowing users to: 1) use controlled vocabularies and create semiautomated computer-parsable insect morphological descriptions; 2) integrate insect morphology into broader fields of research, including ontology-informed phylogenetic methods, logical homology hypothesis testing, evo-devo studies, and genotype to phenotype mapping; and 3) automate the extraction of morphological data from the literature, enabling the generation of large-scale phenomic data, by facilitating the production and testing of informatic tools able to extract, link, annotate, and process morphological data. This descriptive model and its ontological applications will allow for clear and semantically interoperable integration of arthropod phenotypes in biodiversity studies., (© The Author(s) 2023. Published by Oxford University Press, on behalf of the Society of Systematic Biologists. All rights reserved. For permissions, please email: journals.permissions@oup.com.)

Dilaridae are a distinctive and phylogenetically ambiguous neuropteran family. So far, the anatomy of the immature stages remains largely unknown. We examined the 1st instar larvae of Dilar montanus in detail and present results of live observations for the first time. The minute, cryptic larvae display features correlated with their underground lifestyle: for instance, a strongly flattened head, stout antennae, eyelessness, and burrowing forelegs. In contrast to molecular data, several characters suggest a 'dilarid clade' combining Dilaridae with Mantispoidea, for instance a very thin and curved or reduced tentorial bridge, and an elongated postmentum. We found intrinsic antennal muscles and Johnston's organ, the first record of these structures in holometabolous larvae. This proves that the first 2 larval antennomeres are homologous with the scapus and pedicellus. The described characters are discussed and analyzed with an updated matrix of neuropteran larval characters. Alternative scenarios of character evolution are presented. Additionally, we show how the 1st-instar larvae move and feed in the substrate, and also provide a high-resolution video recording of the function of the elongate tubular ovipositor and the egg-laying behavior in an adult female under natural conditions., (© 2023 Institute of Zoology, Chinese Academy of Sciences.)

A new species of the order Zoraptera, Zorotypuskomatsui Matsumura, Maruyama, Ntonifor & Beutel, sp. nov. , is described from Cameroon. The female and male morphology of another species, Z.vinsoni , is re-described, and its new distribution in Madagascar is recorded. A particular focus is on the male postabdominal morphology. This is apparently a crucial body region in the very small order with an extreme variation of the genital apparatus but otherwise a very uniform morphology. The male of the newly described species shares rudimentary male genitalia and well-developed postabdominal projections with the distantly related Spermozorosimpolitus , apparently a result of parallel evolution. Whether males of Z.komatsui also perform external sperm transfer like S.impolitus remains to be shown. The collecting of the material used for this study suggests that the present knowledge of zorapteran species diversity of the Afrotropical region is very fragmentary., Competing Interests: The authors have declared that no competing interests exist., (Yoko Matsumura, Munetoshi Maruyama, Nelson N. Ntonifor, Rolf G. Beutel.)

The morphology of the adult free-living females of Mengenilla moldrzyki and Eoxenos laboulbenei (Strepsiptera, Mengenillidae) was documented with µCT-based 3D reconstructions and histological serial sections. External and internal features of both species are characterized by far-reaching specialization and structural simplification. The well-developed mandibles are moved by large muscles. Other mouthparts and their corresponding musculature are simplified or absent. The brain is partly shifted into the prothorax. It is followed by a single postcerebral ganglionic complex also containing the subesophageal ganglion and an unpaired abdominal nerve. Postcephalic sclerites are absent, except for the plate-like pronotum and small pleural sclerites. Wings and associated muscles are missing. The lumina of the large midgut and the anterior hindgut are disconnected. Seven bulb-shaped Malpighian tubules in M. moldrzyki is the highest number yet described for Strepsiptera. The 10-segmented abdomen lacks appendages. An unpaired birth organ opens ventrally on abdominal segment VII. The entire body cavity is filled with numerous freely floating eggs, 1386 in the specimen of M. moldrzyki and 721 in E. laboulbenei. Genital ducts, defined gonads, and genital glands are missing. The morphology of female Mengenillidae is discussed with respect to sexual dimorphism and structural features of the postembryonic stages. Phylogenetic implications are outlined., (© 2023 The Authors. Journal of Morphology published by Wiley Periodicals LLC.)

Conversion of forewings into hardened covers, elytra, was a ground-breaking morphological adaptation that has contributed to the extraordinary evolutionary success of beetles. Nevertheless, the knowledge of the functional aspects of these structures is still fragmentary and scattered across a large number of studies. Here, we have synthesized the presently available information on the evolution, development, modifications and biological functions of this crucial evolutionary novelty. The formation of elytra took place in the earliest evolution of Coleoptera, very likely already in the Carboniferous, and was achieved through the gradual process of progressive forewing sclerotization and the formation of inward directed epipleura and a secluded sub-elytral space. In many lineages of modern beetles, the elytra have been distinctly modified. This includes multiple surface modifications, a rigid connection or fusion of the elytra, or partial or complete reduction. Beetle elytra can be involved in a very broad spectrum of functions: mechanical protection of hind wings and body, anti-predator strategies, thermoregulation and water saving, water harvesting, flight, hind wing folding, diving and swimming, self-cleaning and burrow cleaning, phoresy of symbiotic organisms, mating and courtship, and acoustic communication. We postulate that the potential of the elytra to take over multiple tasks has enormously contributed to the unparalleled diversification of beetles.

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., (© 2022 The Authors. Journal of Morphology published by Wiley Periodicals LLC.)

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., (© 2022 The Authors. Journal of Morphology published by Wiley Periodicals LLC.)

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., Competing Interests: Stanislav Gorb is an Academic Editor for PeerJ., (© 2022 Jandausch et al.)

Pselaphinae is a large subfamily, comprising over 10 000 species of the megadiverse Staphylinidae (rove beetles). A remarkable feature of this group is the extreme structural diversity of different body regions, especially the head and its appendages. Within Pselaphinae, Clavigeritae stand out as a clade of highly specialized myrmecophiles. We examined internal and external head structures of the clavigerite species Diartiger kubotai Nomura, using state-of-the-art techniques. The cephalic morphology indicates in a phylogenetic context that the loss of eyes in some Clavigeritae was the latest of major evolutionary changes. We compiled the largest set of morphological data ever scored for the subfamily, comprising 155 characters of the head. Parsimony analyses and Bayesian inference yielded a similar phylogenetic pattern, largely congruent with results published previously. We retrieved Pselaphinae as a clade, and Faronitae as sister to all remaining groups of the subfamily. Faronitae are followed by a "Euplectitae grade" and non-monophyletic Goniaceritae, Batrisitae and Pselaphitae. Clavigeritae are monophyletic, but have evolved within the pselaphite grade. The enigmatic Colilodion Besuchet, recently shifted from Clavigeritae to a paraphyletic Pselaphitae, was placed as sister to extant clavigerites based on an array of cephalic synapomorphies. The current classification of Pselaphinae is unstable and deep changes should be made maintaining only monophyletic units, whereas most of the supertribes are paraphyletic. Characters of the head, with a concentration of mouthparts and sensory structures, and essential parts of the digestive tract and the nervous system, are highly informative phylogenetically. Study of internal structures, presently still at a very preliminary stage, obviously is essential for understanding the evolution of Pselaphinae. Future genetic investigations may reveal mechanisms behind the unique structural megadiversity in this exceptional group of rove beetles., (© 2022 Willi Hennig Society.)

The distal leg structures of Zoraptera are documented and discussed with respect to their functional morphology and evolutionary aspects. We investigated eight species using scanning electron microscopy. We analyzed material compositions of the tarsus in three representative species using confocal laser scanning microscopy. When possible, we included both sexes, wing morphs, and nymphs and compared the structures among them. The distal leg structure is unusually uniform across zorapterans regardless of the sex, morphs, and developmental stages. The observed features combine simplification with innovation. The former is likely partially correlated with cryptic microhabitats and miniaturization. Innovation includes a protibial cleaning organ. This is very likely an autapomorphy of Zoraptera. The tarsi are composed of two tarsomeres covered with setae. The pretarsus distally bears an unguitractor plate and well-sclerotized claws. The tarsomeres appear less-sclerotized than the covering setae. The articulation between the basitarsus and tarsomere 2 is hinge-like, implying that tarsomere 2 moves only mediolaterally. The simplified and specialized tarsal morphology is likely suitable for the typical zorapteran microhabitat, under bark. However, the irreversible complete loss of adhesive devices prevented zorapterans to make use of a broader spectrum of environments and was presumably one reason for the species paucity of the group., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

We analyzed patterns of complexity and simplicity in holometabolan insects using parsimony and maximum-likelihood. By contrast with other groups of arthropods (and most other groups of animals), insects have undergone a stepwise process of structural simplification in their evolution. The megadiverse Holometabola are characterized mainly by structurally simplified larvae, which differ strongly from the adults in their morphology and usually also in their life habits. Although smaller groups such as Neuropterida have largely maintained their structural complexity in adults and immature life stages, a series of reductions occurred with the appearance and diversification of Coleopterida, Mecopterida and especially Antliophora. Parasitic Strepsiptera or fleas display conspicuous patterns of reduction in different life stages and body regions, and high degrees of simplification also occur in groups with short-lived adults. Larvae living in moist substrates display far-reaching structural simplifications and also morphological uniformity, especially in the species-rich Diptera, but also in other groups. Liquid feeding leads to correlated simplifications and innovation of adult head structures, especially of the mouthparts. Functional or anatomical dipterism leads to an optimization of the flight apparatus in most holometabolous groups, which is correlated with reductions in one of the pterothoracic segments, and coupled (e.g. by hamuli), partly reduced or transformed wings (e.g. halteres). In flightless groups, the pterothoracic skeleto-muscular apparatus is strongly simplified. In the abdomen of adult females a stepwise reduction of the lepismatoid ovipositor occurs. By contrast, the male genital apparatus often undergoes an extreme diversification. Our evaluations revealed a highly correlated complexity between larval and adult stages., (© 2021 The Authors. Cladistics published by John Wiley & Sons Ltd on behalf of Willi Hennig Society.)

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.

Ants are highly polyphenic Hymenoptera, with at least three distinct adult forms in the vast majority of species. Their sexual dimorphism, however, is overlooked to the point of being a nearly forgotten phenomenon. Using a multimodal approach, we interrogate the near total head microanatomy of the male of Dorylus helvolus, the "sausagefly," and compare it with the conspecific or near-conspecific female castes, the "driver ants." We found that no specific features were shared uniquely between the workers and males to the exclusion of the queens, indicating independence of male and worker development; males and queens, however, uniquely shared several features. Certain previous generalizations about ant sexual dimorphism are confirmed, while we also discover discrete muscular presences and absences, for which reason we provide a coarse characterization of functional morphology. Based on the unexpected retention of a medial carinate line on the structurally simplified mandible of the male, we postulate a series of developmental processes to explain the patterning of ant mandibles. We invoke functional and anatomical principles to classify sensilla. Critically, we observe an inversion of the expected pattern of male-queen mandible development: male Dorylus mandibles are extremely large while queen mandibles are poorly developed. To explain this, we posit that the reproductive-limited mandible phenotype is canalized in Dorylus, thus partially decoupling the queen and worker castes. We discuss alternative hypotheses and provide further comparisons to understand mandibular evolution in army ants. Furthermore, we hypothesize that the expression of the falcate phenotype in the queen is coincidental, that is, a "spandrel," and that the form of male mandibles is also generally coincidental across the ants. We conclude that the theory of ant development and evolution is incomplete without consideration of the male system, and we call for focused study of male anatomy and morphogenesis, and of trait limitation across all castes., (© 2021 The Authors. Journal of Morphology published by Wiley Periodicals LLC.)

The Triassic was a crucial period for the early evolution and diversification of insects, including Coleoptera 1-3 -the most diverse order of organisms on Earth. The study of Triassic beetles, however, relies almost exclusively on flattened fossils with limited character preservation. Using synchrotron microtomography, we investigated a fragmentary Upper Triassic coprolite, which contains a rich record of 3D-preserved minute beetle remains of Triamyxa coprolithica gen. et sp. nov. Some specimens are nearly complete, preserving delicate structures of the legs and antennae. Most of them are congruent morphologically, implying that they are conspecific. Phylogenetic analyses suggest that T. coprolithica is a member of Myxophaga, a small suborder of beetles with a sparse fossil record, and that it represents the only member of the extinct family Triamyxidae fam. nov. Our findings highlight that coprolites can contain insect remains, which are almost as well preserved as in amber. They are thus an important source of information for exploring insect evolution before the Cretaceous-Neogene "amber time window." Treated as food residues, insect remains preserved in coprolites also have important implications for the paleoecology of insectivores, in this case, likely the dinosauriform Silesaurus opolensis., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2021 The Authors. Published by Elsevier Inc. All rights reserved.)

The pselaphine Bergrothia saulcyi shows features seemingly linked with life in deep soil layers, such as greatly reduced and non-functional compound eyes, a sensorium of long tactile setae, long appendages, and flightlessness. However, the tiny beetles occur in forest leaf litter, together with a community of beetles with wings and well-developed eyes. We hypothesize that B. saulcyi moves into deep soil under dry conditions, and returns to upper layers when humidity increases again. Despite the evolutionary cost of a reduced dispersal capacity, this life strategy may be more efficient and less hazardous than moving to different habitats using flight and the visual sense in an environment periodically drying out. We also discuss cephalic features with potential phylogenetic relevance. Plesiomorphies of B. saulcyi include the presence of anterior tentorial arms, well-developed labral retractors, and a full set of extrinsic maxillary and premental muscles. Apomorphic cephalic features support clades Protopselaphinae + Pselaphinae, and Pselaphinae. A conspicuous derived condition, the clypeo-ocular carina, is a possible synapomorphy of Batrisitae and genera assigned to Goniaceritae. A complex triple set of cephalic glands found in B. saulcyi is similar to a complex identified in the strict myrmecophile Claviger testaceus (Clavigeritae). It is conceivable that glands linked with food uptake in free-living pselaphines were genetically re-programmed in ancestors of inquilines, to enable them to appease the host ants. We suggest that behavioral studies are necessary to understand the poorly known life habits of B. saulcyi. Additional information is required to explain why a species with irreversibly reduced visual sense and other adaptations typical of endogean or cave-dwelling beetles was only collected from the upper leaf litter layer., (© 2021 The Authors. Journal of Morphology published by Wiley Periodicals LLC.)

Clavigeritae is a group of obligate myrmecophiles of the rove beetle subfamily Pselaphinae (Staphylinidae). Some are blind and wingless, and all are believed to depend on ant hosts through feeding by trophallaxis. Phylogenetic hypotheses suggest that their ancestors, as are most pselaphines today, were free-living predators. Morphological alterations required to transform such beetles into extreme myrmecophiles were poorly understood. By studying the cephalic morphology of Claviger testaceus, we demonstrate that profound changes in all mouthpart components took place during this process, with a highly unusual connection of the maxillae to the hypopharynx, and formation of a uniquely transformed labium with a vestigial prementum. The primary sensory function of the modified maxillary and labial palps is reduced, and the ventral mouthparts transformed into a licking/'sponging' device. Many muscles have been reduced, in relation to the coleopteran groundplan or other staphylinoids. The head capsule contains voluminous glands whose appeasement secretions are crucial for the beetle survival in ant colonies. The brain, in turn, has been shifted into the neck region. The prepharyngeal dilator is composed of an entire series of bundles. However, the pharynx does not show any peculiar adaptations to taking up liquid food. We demonstrate that far-reaching cephalic modifications characterize C. testaceus, and that the development of appeasement glands and adaptation of the mouthparts to trophallaxis determine the head architecture of this extreme myrmecophile., (© 2020 Wiley Periodicals LLC.)

The distal parts of the legs of Sceliphron caementarium (Sphecidae) and Formica rufa (Formicidae) are documented and discussed with respect to phylogenetic and functional aspects. The prolegs of Hymenoptera offer an array of evolutionary novelties, mainly linked with two functional syndromes, walking efficiently on different substrates and cleaning the body surface. The protibial-probasitarsomeral cleaning device is almost always well-developed. A complex evolutionary innovation is a triple set of tarsal and pretarsal attachment devices, including tarsal plantulae, probasitarsomeral spatulate setae, and an arolium with an internal spring-like arcus, a dorsal manubrium, and a ventral planta. The probasitarsal adhesive sole and a complex arolium are almost always preserved, whereas the plantulae are often missing. Sceliphron has retained most hymenopteran ground plan features of the legs, and also Formica, even though the adhesive apparatus of Formicidae shows some modifications, likely linked to ground-oriented habits of most ants. Plantulae are always absent in extant ants, and the arolium is often reduced in size, and sometimes vestigial. The arolium contains resilin in both examined species. Additionally, resilin enriched regions are also present in the antenna cleaners of both species, although they differ in which of the involved structures is more flexible, the calcar in Sceliphron and the basitarsal comb in Formica. Functionally, the hymenopteran distal leg combines (a) interlocking mechanisms (claws, spine-like setae) and (b) adhesion mechanisms (plantulae, arolium). On rough substrate, claws and spine-like setae interlock with asperities and secure a firm grip, whereas the unfolding arolium generates adhesive contact on smooth surfaces. Differences of the folded arolium of Sceliphron and Formica probably correlate with differences in the mechanism of folding/unfolding., (© 2020 The Authors. Journal of Morphology published by Wiley Periodicals, Inc.)

Background: The latest advancements in DNA sequencing technologies have facilitated the resolution of the phylogeny of insects, yet parts of the tree of Holometabola remain unresolved. The phylogeny of Neuropterida has been extensively studied, but no strong consensus exists concerning the phylogenetic relationships within the order Neuroptera. Here, we assembled a novel transcriptomic dataset to address previously unresolved issues in the phylogeny of Neuropterida and to infer divergence times within the group. We tested the robustness of our phylogenetic estimates by comparing summary coalescent and concatenation-based phylogenetic approaches and by employing different quartet-based measures of phylogenomic incongruence, combined with data permutations., Results: Our results suggest that the order Raphidioptera is sister to Neuroptera + Megaloptera. Coniopterygidae is inferred as sister to all remaining neuropteran families suggesting that larval cryptonephry could be a ground plan feature of Neuroptera. A clade that includes Nevrorthidae, Osmylidae, and Sisyridae (i.e. Osmyloidea) is inferred as sister to all other Neuroptera except Coniopterygidae, and Dilaridae is placed as sister to all remaining neuropteran families. Ithonidae is inferred as the sister group of monophyletic Myrmeleontiformia. The phylogenetic affinities of Chrysopidae and Hemerobiidae were dependent on the data type analyzed, and quartet-based analyses showed only weak support for the placement of Hemerobiidae as sister to Ithonidae + Myrmeleontiformia. Our molecular dating analyses suggest that most families of Neuropterida started to diversify in the Jurassic and our ancestral character state reconstructions suggest a primarily terrestrial environment of the larvae of Neuropterida and Neuroptera., Conclusion: Our extensive phylogenomic analyses consolidate several key aspects in the backbone phylogeny of Neuropterida, such as the basal placement of Coniopterygidae within Neuroptera and the monophyly of Osmyloidea. Furthermore, they provide new insights into the timing of diversification of Neuropterida. Despite the vast amount of analyzed molecular data, we found that certain nodes in the tree of Neuroptera are not robustly resolved. Therefore, we emphasize the importance of integrating the results of morphological analyses with those of sequence-based phylogenomics. We also suggest that comparative analyses of genomic meta-characters should be incorporated into future phylogenomic studies of Neuropterida.

Endoparasitic larval stages of Eoxenos laboulbenei were documented with different techniques, with a main focus on the male tertiary larva. Two discrete endoparasitic stages occur, the secondary and the tertiary larva. The presence of large compound eyes and externally visible wing buds in the tertiary larva is a unique feature within Holometabola. The brain with large optic lobes is followed by a single postcephalic ganglionic complex. The cephalic musculature is greatly reduced but pharyngeal dilators and muscles associated with the mouth field are present. Postcephalic sclerites are absent except for the pronotum. The segmented legs bear filiform pretarsal claws. The indirect flight muscles fill up a large part of the metathorax. The 10-segmented abdomen lacks appendages. Pleural folds are present on the thorax and abdomen. The digestive tract is characterized by a very short oesophagus. The large midgut and the narrow hindgut are disconnected. Six short Malpighian tubules are present. Large testes fill out almost the entire abdomen. In contrast to the tertiary larva, the muscles of the secondary larva are not fully differentiated. Cephalic appendages are present as bud-shaped anlagen. The legs lack a pretarsal claw. The developmental transformations are outlined and discussed, also with respect to phylogenetic implications., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

The order Coleoptera (beetles) is arguably the most speciose group of animals, but the evolutionary history of beetles, including the impacts of plant feeding (herbivory) on beetle diversification, remain poorly understood. We inferred the phylogeny of beetles using 4,818 genes for 146 species, estimated timing and rates of beetle diversification using 89 genes for 521 species representing all major lineages and traced the evolution of beetle genes enabling symbiont-independent digestion of lignocellulose using 154 genomes or transcriptomes. Phylogenomic analyses of these uniquely comprehensive datasets resolved previously controversial beetle relationships, dated the origin of Coleoptera to the Carboniferous, and supported the codiversification of beetles and angiosperms. Moreover, plant cell wall-degrading enzymes (PCWDEs) obtained from bacteria and fungi via horizontal gene transfers may have been key to the Mesozoic diversification of herbivorous beetles-remarkably, both major independent origins of specialized herbivory in beetles coincide with the first appearances of an arsenal of PCWDEs encoded in their genomes. Furthermore, corresponding (Jurassic) diversification rate increases suggest that these novel genes triggered adaptive radiations that resulted in nearly half of all living beetle species. We propose that PCWDEs enabled efficient digestion of plant tissues, including lignocellulose in cell walls, facilitating the evolution of uniquely specialized plant-feeding habits, such as leaf mining and stem and wood boring. Beetle diversity thus appears to have resulted from multiple factors, including low extinction rates over a long evolutionary history, codiversification with angiosperms, and adaptive radiations of specialized herbivorous beetles following convergent horizontal transfers of microbial genes encoding PCWDEs., Competing Interests: The authors declare no competing interest., (Copyright © 2019 the Author(s). Published by PNAS.)

The morphology of mature larvae of Sisyra nigra was studied and documented with a broad spectrum of techniques. Special emphasis is on the cephalic anatomy and on the digestive tract. Cephalic structures are highly modified, with numerous autapomorphic conditions, including a globular head capsule, an extended area with large cornea lenses, a massive tentorium, a strongly developed prepharyngeal pumping apparatus with a horizontal arrangement of dilators, a sharp bend between the prepharynx and pharynx, and an unusual filter apparatus at the entrance of the large crop. The thoracic and abdominal muscle sets, and the legs are largely unmodified. Postcephalic apomorphies are conspicuous tergal setiferous tubercles, trifid setiferous pleural projections, single pretarsal claws, zigzag-shaped abdominal tracheal gills, and a dense vestiture of setae on the terminal abdominal segments. Mandibulo-maxillary stylets curved outwards are an unusual apomorphy also found in the semiaquatic larvae of Osmylidae. Semiaquatic or aquatic habits and secondarily multisegmented antennae are potential synapomorphies of these two groups and Nevrorthidae (Osmyloidea). A sistergroup relationship between Sisyridae and Nevrorthidae suggests that fully aquatic habits of larvae may be a synapomorphy of both families. A specialized terminal antennal seta is a potential groundplan apomorphy of Neuroptera, with secondary loss in Nevrorthidae and Ithonidae + Myrmeleontiformia, respectively. A trumpet-shaped empodium is likely an apomorphy of Neuroptera excluding Coniopterygidae and Osmyloidea, and the secondary loss an apomorphy of Ithonidae on one hand, and Myrmeleontiformia excl. Psychopsidae on the other., (© 2019 The Authors. Journal of Morphology published by Wiley Periodicals, Inc.)

The thoracic morphology of the troglobiontic leiodid species Troglocharinus ferreri (Cholevinae, Leptodirini) is described and documented in detail. The features are mainly discussed with respect to modifications linked with subterranean habits. Troglocharinus is assigned to the moderately modified pholeuonoid morphotype. The body is elongated and slender compared to epigean leiodids and also cave-dwelling species of Ptomaphagini. The legs are elongated, especially the hindlegs, though to a lesser degree than in the most advanced troglobiontic species. The prothorax is moderately elongated but otherwise largely unmodified. Its muscular system is strongly developed, with more muscle bundles that in free-living staphylinoid or hydrophiloid species. The pterothorax is greatly modified, especially the metathoracic flight apparatus. The meso- and metathoracic elements of the elytral locking device are well-developed, whereas the other notal parts are largely reduced. The mesonotum is simplified, with the triangular scutellar shield as the only distinctly developed part. The mesothoracic musculature is strongly reduced, with only 6 muscles compared to 12 or 13 in free-living staphylinoid or hydrophiloid species. The metanotum is greatly reduced, without a recognizable subdivision into prescutum scutum and scutellum. It is strongly narrowing laterally and lacks notal wing processes and other wing-related elements, but well-developed alacristae are present. The wings are reduced to small membranous flap-like structures inserted at the posterior end of the metanotum. A metapostnotum is not developed. Like in the case of the head, cave dwelling species of the related Ptomaphagini and Leptodirini show different trends of adaptations, with a compact ovoid or navicular body shape in the former, and a distinct trend towards elongation of the body and appendages in the latter tribe. Structural affinities of the thoraces of T. ferreri and the troglobiontic trechine carabid Sinaphaenops wangorum are mainly due to the reduced flight apparatus. The degree of muscle reduction in the pterothorax is very similar in both species., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

A new species of the order Zoraptera, Zorotypus pecten sp. n., is described from mid-Cretaceous Burmese amber. It is tentatively assigned to the subgenus Octozoros based on 8-segmented antenna. A Gondwanan origin for Zoraptera is discussed based on the geographic distribution of extant and fossil zorapterans.

Leiodidae are the second largest subterranean radiation of beetles at family rank. To explore morphological trends linked with troglobiontic habits and characters with potential phylogenetic significance, the head of the cave-dwelling species Troglocharinus ferreri (Cholevinae, Leptodirini) was examined in detail. Overall, the general pattern is similar to what is found in Catops ventricosus (Cholevini). Shared apomorphic features include a fully exposed anterolateral concavity containing the antennal socket, a distinct bead above this depression, a bilobed lip-like structure anterad the labrum, a flat elevated portion of the ventral mandibular surface, and a ventral process at the proximomesal edge of this mandibular area. The tentorial structures are well-developed as in C. ventricosus, with a large laminatentorium and somewhat shortened dorsal arms. The mouthparts are largely unmodified, with the exception of unusually well-developed extrinsic maxillary muscles. Features of T. ferreri obviously linked with subterranean habits are the complete lack of compound eyes, circumocular ridges, and optic lobes. A series of characters is similar to conditions found in other genera of Leptodirini: the head capsule completely lacks a protruding ocular region, a distinct neck is missing, the transverse occipital crest is indistinct, and the antennae are elongate and lack a distinct club. Two different trends of cephalic transformations occur in troglobiontic Leptodirini, with some genera like Troglocharinus and Leptodirus having elongated head capsules and antennae, and others having broadened, more transverse heads. In contrast, the modifications are more uniform in the closely related Ptomaphagini, with a pattern distinctly differing from Leptodirini: the head is transverse, with a distinctly protruding ocular region, a distinct transverse occipital crest, and a very narrow neck region., (© 2019 Wiley Periodicals, Inc.)

The beetle superfamily Dytiscoidea, placed within the suborder Adephaga, comprises six families. The phylogenetic relationships of these families, whose species are aquatic, remain highly contentious. In particular the monophyly of the geographically disjunct Aspidytidae (China and South Africa) remains unclear. Here we use a phylogenomic approach to demonstrate that Aspidytidae are indeed monophyletic, as we inferred this phylogenetic relationship from analyzing nucleotide sequence data filtered for compositional heterogeneity and from analyzing amino-acid sequence data. Our analyses suggest that Aspidytidae are the sister group of Amphizoidae, although the support for this relationship is not unequivocal. A sister group relationship of Hygrobiidae to a clade comprising Amphizoidae, Aspidytidae, and Dytiscidae is supported by analyses in which model assumptions are violated the least. In general, we find that both concatenation and the applied coalescent method are sensitive to the effect of among-species compositional heterogeneity. Four-cluster likelihood-mapping suggests that despite the substantial size of the dataset and the use of advanced analytical methods, statistical support is weak for the inferred phylogenetic placement of Hygrobiidae. These results indicate that other kinds of data (e.g. genomic meta-characters) are possibly required to resolve the above-specified persisting phylogenetic uncertainties. Our study illustrates various data-driven confounding effects in phylogenetic reconstructions and highlights the need for careful monitoring of model violations prior to phylogenomic analysis., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Mengenillidae is a small, basal family of Strepsiptera, mainly characterized by free-living females in contrast to the endoparasitic females of Stylopidia. Here, we describe external and internal structures of the female abdomen of Eoxenos laboulbenei (Mengenillidae). The external morphology was examined and documented using microphotography. Internal structures were reconstructed three-dimensionally using a μCT-data set. The morphologically simplified abdomen comprises 10 segments. The integument is weakly sclerotized and flexible. Spiracles are present dorsolaterally on segments I-VII. Segment VII bears the posteroventral birth opening and the small abdominal segment X carries the anus at its apex. Numerous eggs float freely in the hemolymph. The musculature of segments I-IV is composed of ventral and dorsal longitudinal muscle bundles, strongly developed paramedial dorsoventral muscles and a complex meshwork of small pleural muscles, with minimal differences between the segments. Segments V-X contain more than 50 individual muscles, even though the musculature as a whole is weakly developed. Even though it is not involved in processing food, the digestive tract is well-developed. Its postabdominal section comprises a part of the midgut and the short hindgut. The midgut fills a large part of the postabdominal lumen. The lumina of the midgut and hindgut are not connected. Five or six nodular Malpighian tubules open into the digestive tract at the border region between the midgut and hindgut. The birth organ below the midgut releases the primary larvae after hatching via the birth opening at segment VII. It is likely derived from primary female genital ducts. The presence of six additional birth organs of segments I-VI are de novo formations and a groundplan apomorphy of Stylopidia, the large strepsipteran subgroup with endoparasitic females. The loss of the primary birth organ of segment VII is an apomorphy of Stylopiformia (Stylopidia excl. Corioxenidae)., (© 2019 Wiley Periodicals, Inc.)

A new insect species (†Bittacopsocus megacephalus Beutel, Prokop, Müller et Pohl gen. et sp. nov.) is described, based on a single small male (ca. 2.5 mm) embedded in mid Cretaceous Burmese amber. The species shows some resemblance with the mecopteran family Bittacidae, mainly due to strongly elongated and thin legs. However, the structural affinities are apparently due to convergency. Different features, but especially the mouthparts and the pattern of wing venation, indicate that the species belongs to the extinct order †Permopsocida (?Archipsyllidae). However, it differs markedly from all species previously described in this extinct group. The very thin and strongly elongated legs are probably autapomorphic. A very unusual feature is the antenna with only seven segments and extremely elongated flagellomeres. The two pairs of wings are unusually narrow. M and CuA are basally fused. Proximal rows of spines, two series of closed cells, and a distinctly increased number of terminal branches of M are present in the forewings, in contrast to other archipsyllid genera. It is conceivable that Bittacopsocus megacephalus used its long legs to rest suspended in the vegetation like Bittacus. The head structures tentatively suggest predatory behavior but the feeding habits are unclarified yet.

Despite the ecological significance of ants and the intensive research attention they have received, thorough treatments of the anatomy and functional morphology are still scarce. In this study we document the head morphology of workers of the myrmicine Wasmannia affinis with optical microscopy, μ-computed tomography, scanning electron microscopy, and 3D reconstruction, providing the first complete anatomical treatment of an ant head with a broad array of modern techniques. We discuss the potential of the applied methods to generate detailed and well-documented morphological data sets with increased efficiency. We also address homology problems, particularly in the context of the cephalic digestive tract. According to our analyses the "pharynx" of previous ant studies is homologous to the prepharynx of other insects. We also discuss the phylogenetic potential and functional significance of the observed characters, with internal features such as tentorium and musculature discussed for the first time. Our investigation underlines that detailed anatomical data for Formicidae are still very fragmentary, which in turn limits our understanding of the major design elements underlying the ant bauplan. We attempt to provide a template for further anatomical studies, which will help to understand the evolution of this fascinating group on the phenotypic level., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

The current state of knowledge of the suprageneric relationships in Cholevinae is either derived from informal evaluations of putative synapomorphies or based on molecular studies with limited taxonomic sampling. Here we assessed the higher-level relationships in this subfamily based on a phylogenetic analysis of 97 morphological characters scored for 93 terminals, representing all tribes. Both parsimony and Bayesian analyses were used. The monophyletic origin of Cholevinae was corroborated, except for the unexpected inclusion of Leptinus in the implied weighting analysis. Eucatopini + Oritocatopini were retrieved as basal branches in the evolution of Cholevinae. The monophyletic origin of all remaining Cholevinae was confirmed, which is consistent with molecular evidence. Anemadini was non-monophyletic, in accordance with earlier hypotheses. Cholevini was rendered non-monophyletic by the uncertain inclusion of Prionochaeta and the consistent exclusion of Cholevinus. A close affinity of Ptomaphagini to Sciaphyini and Leptodirini was suggested, although the position of Sciaphyes remains uncertain. The phylogenetic hypothesis of Cholevinae provided here is the most comprehensive presently available. The list of characters shows that a substantial part of the data was obtained from the ventral side. This is a strong argument for a detailed pictorial documentation of the ventral body parts in taxonomic descriptions, in contrast to the common practice of only illustrating the dorsal habitus of the beetles., (© The Willi Hennig Society 2017.)

The larva of Lepicerus inaequalis Motschulsky was described by Lawrence et al. (2013) based on several early instars and one late instar collected among wet leaves and debris near Gamboa, Panama. The identification was based on collection of an adult Lepicerus in a similar habitat nearby and a combination of characters found in other myxophagan immatures but not known in other beetle larvae. We accepted this identification with some reservations, but a misinterpretation of one feature in the original description plus an unexpected new source of evidence makes it likely that our identification was incorrect. The one misinterpreted feature in this larva was the retraction of the ventral mouthparts. Reexamining the larvae, it was found that a pair of tendons extending mesally from the hypostomal rods were misinterpreted as maxillary bases. The mouthparts are definitely protracted, which is expected with long hypostomal rods. The new source of evidence is somewhat complicated, as explained below.

In this review the presently available morphological data on primary larvae of Strepsiptera are interpreted with respect to effects of miniaturization, but also their possible functional or phylogenetic background. The morphology of the 1st instars is mainly affected by functional constraints linked with parasitism but also by very distinct effects of miniaturization. The latter include modifications of the cephalic cuticle, the extremely limited free space in the body lumen, the shift of origins of cephalic muscles to the thorax, a reduced number of cephalic and thoracic muscles, extensions of muscles with cell bodies and other organelles, and an extreme concentration of the entire central nervous system in the middle region of the body. Pad-like adhesive structures on the distal leg segment and the abdominal jumping apparatus are clearly linked with the necessity to attach to a potential host but would not function in distinctly larger organisms., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Pterothoracic structures of the minute ptiliid Nephanes titan were examined and described in detail. Effects of miniaturization and the phylogenetic and functional background are discussed. Apomorphies shared with Hydraenidae are the large metascutal shield, the fringe of setae along the posterior edge of the wings, and the fusion of the mesoventrite with the mesanepisternum. Autapomorphies of Ptiliidae are the highly modified feather-like wings, the strongly elongated alacristae, the loss of the mesotrochantin, the enlarged metathoracic pleural wing joint, and the simplification of the direct flight musculature. Most phylogenetically relevant features are linked with miniaturization, especially the modifications of the wings and skeleton, for instance the reduced wing membrane or the simplified metanotum without distinct notal wing processes. Ptiliids show flight characteristics that distinctly differ from what is known in other insects, such as an unusually high amplitude of beats of the elytra, and a unique trajectory of wing return movements, as well as the presence of upper and lower claps. A comparison of cross-sections of ptiliid principal flight muscles with those of larger staphyliniform beetles suggests that muscles of the tiniest beetles are relatively smaller. This may reflect the higher aerodynamic efficiency of ptiliid feather wings compared to the common membranous wings found in other groups., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Hemipteroid insects (Paraneoptera), with over 10% of all known insect diversity, are a major component of terrestrial and aquatic ecosystems. Previous phylogenetic analyses have not consistently resolved the relationships among major hemipteroid lineages. We provide maximum likelihood-based phylogenomic analyses of a taxonomically comprehensive dataset comprising sequences of 2,395 single-copy, protein-coding genes for 193 samples of hemipteroid insects and outgroups. These analyses yield a well-supported phylogeny for hemipteroid insects. Monophyly of each of the three hemipteroid orders (Psocodea, Thysanoptera, and Hemiptera) is strongly supported, as are most relationships among suborders and families. Thysanoptera (thrips) is strongly supported as sister to Hemiptera. However, as in a recent large-scale analysis sampling all insect orders, trees from our data matrices support Psocodea (bark lice and parasitic lice) as the sister group to the holometabolous insects (those with complete metamorphosis). In contrast, four-cluster likelihood mapping of these data does not support this result. A molecular dating analysis using 23 fossil calibration points suggests hemipteroid insects began diversifying before the Carboniferous, over 365 million years ago. We also explore implications for understanding the timing of diversification, the evolution of morphological traits, and the evolution of mitochondrial genome organization. These results provide a phylogenetic framework for future studies of the group., Competing Interests: The authors declare no conflict of interest.

Twisted winged insects (Strepsiptera) are a highly specialized small order of parasitic insects. Whether parasitism developed at an early or late stage in the evolution of the group was unknown. Here we record and describe the first definite Mesozoic strepsipteran primary larva embedded in Burmese amber (∼99 million years ago). This extends the origin of parasitism back by at least ∼50 million years, and reveals that this specialized life style has evolved in the Mesozoic or even earlier in the group. The extremely small first instar displays all diagnostic characters of strepsipteran immatures of this stage and is nearly identical with those of Mengenillidae, one of the most "ancestral" extant strepsipteran taxa. This demonstrates a remarkable evolutionary stasis over  100 million years. The new finding strongly weakens the case of small larvae embedded in Cretaceous amber interpreted as strepsipteran immatures. They differ in many structural features from extant strepsipteran primary larvae and are very likely parasitic beetle larvae., Competing Interests: The authors declare there are no competing interests.

A new species of the order Zoraptera, Zorotypus hirsutus Mashimo sp. n., is described from mid-Cretaceous Burmese amber. The specimen is tentatively assigned to the subgenus Octozoros Engel based on number of antennomeres reduced from nine to eight. It is characterized by an unusually strong setation, appearing much more hirsute than other extant or extinct species of the order. Other unusual autapomorphic features are an elongated head capsule with a concave genal region and very slender, elongate antennomeres. The discovery of this aberrant species suggests that the morphological diversity of Zoraptera was much higher than previously expected. For a reliable placement of Zorotypus hirsutus the discovery of males and a robust species level phylogeny would be required.

External and internal thoracic structures of two carabid species (Trechini) were examined and documented with different techniques. The study has a main focus on the eyeless cave-dwelling specialist Sinaphaenops wangorum, but detailed information is also provided for a species occurring in cave entrances. The phylogenetic background of the structural features of the thoracic skeletomuscular system was addressed. The thoracic morphology of the examined species was compared to conditions observed in previously studied carabids and non-related subterranean leiodids (Staphylinoidea) in order to identify cave adaptations. Main thoracic character complexes linked with cavernicolous habits in Trechini are elongation of the pro- and mesothorax and the legs, and a complete and irreversible reduction of the flight apparatus. The lost flight capacity is linked with a far reaching modification of skeletal elements of the metathorax including a strongly shortened and simplified metanotum, a shortened metaventrite, and completely reduced wings and sclerites of the wing base. The elongate prothorax together with the long and slender head and elongated legs distinctly increases the activity range in the subterranean lightless environment, which likely facilitates foraging of the carnivorous beetles. Some of the observed features like wing loss and elongation of the anterior thorax and legs are also found in some cave-dwelling Leiodidae (Leptodirini), whereas some other subterranean members of the staphylinoid family have a compact body and legs of normal length. In contrast to the predaceous Trechini, Leptodirini are scavengers., (Copyright © 2018. Published by Elsevier Ltd.)

The legs of the primary larva of Mantispa aphavexelte, parasite in egg sacks of spiders, were examined using scanning electron microscopy (SEM), histology and confocal laser scanning microscopy (CLSM). The leg morphology is described in detail, including intrinsic muscles. Functional adaptations of the leg attachment devices are discussed, especially regarding the material composition. For example, a sole-like flexible ventral tarsal surface containing resilin is combined with sclerotized pseudo-claws. This likely enables the larvae to cope with surface structures on the spider's body, with substrates on the ground, and also with various structural elements in the spider's nest. The leg morphology is evaluated with respect to phylogenetic affinities. A trumpet-shaped, elongated empodium has likely evolved early in the evolution of Neuroptera and may consequently belong to the groundplan of a large subgroup of the order. It characterizes most groups of the hemerobiform lineage and is also present in the myrmeleontiform Psychopsidae. The presence of a tarsal protrusion resembling a pretarsus confirms the monophyletic origin of Mantispoidea. A single fixed tooth and a specific surface structure are potential autapomorphies of Mantispidae. A distal tibial subunit partly separated from the main part of the leg segment is an apomorphy only described for larvae of M. aphavexelte., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Background: Gyrinidae are a charismatic group of highly specialized beetles, adapted for a unique lifestyle of swimming on the water surface. They prey on drowning insects and other small arthropods caught in the surface film. Studies based on morphological and molecular data suggest that gyrinids were the first branch splitting off in Adephaga, the second largest suborder of beetles. Despite its basal position within this lineage and a very peculiar morphology, earliest Gyrinidae were recorded not earlier than from the Upper Triassic., Results: Tunguskagyrus. with the single species Tunguskagyrus planus is described from Late Permian deposits of the Anakit area in Middle Siberia. The genus is assigned to the stemgroup of Gyrinidae, thus shifting back the minimum age of this taxon considerably: Tunguskagyrus demonstrates 250 million years of evolutionary stability for a very specialized lifestyle, with a number of key apomorphies characteristic for these epineuston predators and scavengers, but also with some preserved ancestral features not found in extant members of the family. It also implies that major splitting events in this suborder and in crown group Coleoptera had already occurred in the Permian. Gyrinidae and especially aquatic groups of Dytiscoidea flourished in the Mesozoic (for example Coptoclavidae and Dytiscidae) and most survive until the present day, despite the dramatic "Great Dying" - Permian-Triassic mass extinction, which took place shortly (in geological terms) after the time when Tunguskagyrus lived., Conclusions: Tunguskagyrus confirms a Permian origin of Adephaga, which was recently suggested by phylogenetic "tip-dating" analysis including both fossil and Recent gyrinids. This also confirms that main splitting events leading to the "modern" lineages of beetles took place before the Permian-Triassic mass extinction. Tunguskagyrus shows that Gyrinidae became adapted to swimming on the water surface long before Mesozoic invasions of the aquatic environment took place (Dytiscoidea). The Permian origin of Gyrinidae is consistent with a placement of this highly derived family as the sister group of all remaining adephagan groups, as suggested based on morphological features of larvae and adults and recent analyses of molecular data.

A new species of order Zoraptera, Zorotypus asymmetristernum Mashimo, n. sp., is described from Kakamega, Kenya, with its major diagnostic features and characteristics of the egg described and illustrated. The new species represents the sixth zorapteran species from the Afrotropic ecozone. A brief discussion on vestigial eye spots of apteron individuals and a key to the species of the Afrotropic ecozone are provided.

Insects use different parts of their body to cling to mating partners, to catch prey, or to defend themselves, in most cases the mouthparts or the legs. However, in 400 million years of evolution [1, 2], specialized devices were independently acquired in several groups to adopt these tasks, as for instance modified legs in mantids, assassin bugs or stick insects [3-5], or clasping antennae of the globular springtails [6]. So far, no known species used the neck region between the head and thorax in one of these functional contexts. Here we describe females of †Caputoraptor elegans, a very unusual, presumably predacious insect discovered in approximately 100-million-year-old [7] Burmese amber. Based on several morphological features, we conclude that this species lived in the foliage of trees or bushes. A unique feature of the new taxon is a scissor-like mechanism formed by wing-like extensions on the posterior head and corresponding serrated edges of the dorsal sclerite of the first thoracic segment. Based on the specific structure of the apparatus, we conclude that it was probably used by females to hold on to males during copulation. A defensive or prey-catching function appears less likely. A similar mechanism did not evolve in any other known known group of extant or extinct insects., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

The salivary glands of two species of Zoraptera, Zorotypus caudelli and Zorotypus hubbardi, were examined and documented mainly using transmission electron microscopy (TEM). The results obtained for males and females of the two species are compared and functional aspects related to ultrastructural features are discussed. The salivary glands are divided into two regions: the secretory cell region and the long efferent duct, the latter with its distal end opening in the salivarium below the hypopharyngeal base. The secretory region consists of a complex of secretory cells provided with microvillated cavities connected by short ectodermal ducts to large ones, which are connected with the long efferent duct. The secretory cell cytoplasm contains a large system of rough endoplasmic reticulum and Golgi apparatus producing numerous dense secretions. The cells of the efferent duct, characterized by reduced cytoplasm and the presence of long membrane infoldings associated with mitochondria, are possibly involved in fluid uptaking from the duct lumen., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Techniques currently used in insect morphology are outlined briefly. Scanning electron microscopy (SEM) and microphotography are used mainly for documenting external features, the former providing more information on tiny surface structures and the latter on coloration, transparency and degree of sclerotization. A broad spectrum of methods is now available for anatomical studies: histological serial sections, confocal laser scanning microscopy (CLSM), light-sheet fluorescence microscopy (LSFM), serial block-face scanning electron microscopy (SBFSEM), dual beam scanning electron microscopy (FIB-SEM), nuclear magnetic resonance imaging (NMRI), and μ-computed tomography (micro-CT). The use of SBFSEM and FIB-SEM is restricted to extremely small samples. NMRI is used mainly in in vivo studies. Micro-computed tomography, in combination with computer-based reconstruction, has greatly accelerated the acquisition of high quality data in a phylogenetic context. Morphology will continue to play a vital role in phylogenetic and evolutionary investigations. It provides independent data for checking the plausibility of molecular phylogenies and is the only source of information for placing extinct taxa. It is the necessary basis for reconstructing character evolution on the phenotypic level and for developing complex evolutionary scenarios. Computer-based anatomical ontologies are an additional future perspective of morphological work., (Copyright © 2016 Elsevier Inc. All rights reserved.)