Beetles constitute the most biodiverse animal order with over 380 000 described species and possibly several million more yet unnamed. Recent phylogenomic studies have arrived at considerably incongruent topologies and widely varying estimates of divergence dates for major beetle clades. Here, we use a dataset of 68 single-copy nuclear protein-coding (NPC) genes sampling 129 out of the 193 recognized extant families as well as the first comprehensive set of fully justified fossil calibrations to recover a refined timescale of beetle evolution. Using phylogenetic methods that counter the effects of compositional and rate heterogeneity, we recover a topology congruent with morphological studies, which we use, combined with other recent phylogenomic studies, to propose several formal changes in the classification of Coleoptera: Scirtiformia and Scirtoidea sensu nov ., Clambiformia ser. nov. and Clamboidea sensu nov. , Rhinorhipiformia ser. nov ., Byrrhoidea sensu nov. , Dryopoidea stat. res. , Nosodendriformia ser. nov. and Staphyliniformia sensu nov ., and Erotyloidea stat. nov ., Nitiduloidea stat. nov . and Cucujoidea sensu nov., alongside changes below the superfamily level. Our divergence time analyses recovered a late Carboniferous origin of Coleoptera, a late Palaeozoic origin of all modern beetle suborders and a Triassic–Jurassic origin of most extant families, while fundamental divergences within beetle phylogeny did not coincide with the hypothesis of a Cretaceous Terrestrial Revolution.

Thorny lacewings (Rhachiberothidae) are currently distributed only within Africa, whereas they are prevalent in the fossil record of various Cretaceous ambers across the Northern Hemisphere, with a handful of the fossil records from some Eocene European ambers. Four rhachiberothid species in four extinct genera are known from the mid-Cretaceous amber of northern Myanmar. Here, we report further examples of the remarkable palaeodiversity of this group from the same amber deposit, adding the four new fossil genera and seven new species:Acanthoberotha cuspisgen. et sp. nov.,Astioberotha falcipesgen. et sp. nov.,Stygioberotha siculiferagen. et sp. nov.,Uranoberotha chariessagen. et sp. nov.,Creagroparaberotha cuneatasp. nov.,Micromantispa galeatasp. nov. andM.spicatasp. nov. Based on a series of well-preserved specimens, we discuss the fine details of the raptorial forelegs and genital segments, which may be important for elucidating the phylogenetic relationships among genera. Our findings reveal an unexpectedly diverse assemblage of thorny lacewings in the Cretaceous System, highlighting the morphologically diverse rhachiberothids in Burmese amber. The discovery of seven additional rhachiberothid species in Myanmar amber suggests the potential for much higher diversity and abundance of the Cretaceous rhachiberothids than previously documented. Furthermore, morphological variation in the raptorial forelegs was found to be extremely diverse among the Burmese amber paraberothines, especially in terms of the size, number and shape of spines (or spine-like setae) on the inner edges of protibia, and the morphological structure of the probasitarsus.

Mantispoidea (Insecta, Neuroptera) are well-known for the hypermetamorphic larval development and for most adults having praying mantis-like raptorial forelegs. Currently, this superfamily comprises Berothidae (beaded lacewings) and three raptorial mantispoid families: Rhachiberothidae (thorny lacewings), Dipteromantispidae and Mantispidae (mantidflies or mantid lacewings). It includes about 530 extant species in 74 genera, and 143 extinct species in 97 genera from the Upper Triassic to the Miocene. Berothidae, well-known for some adults with scale-like setae on the female wings, currently includes 119 extant species in 26 genera, and 59 extinct species in 37 genera from the Upper Triassic to the Eocene. Rhachiberothidae represents the relictual group of Mantispoidea, comprising only 14 extant species across four genera, which are confined to the Afrotropical Region. However, the abundant fossil records (28 species and 21 genera), especially from the Cretaceous, highlight the past glory of this family. The Cretaceous dipteran-like family Dipteromantispidae, comprising ten species across nine genera, remains enigmatic in terms of its phylogenetic status. Mantispidae, the largest family within Mantispoidea, comprises approximately 395 extant species across 44 genera and 46 extinct species in 30 genera, ranging from the Lower Jurassic to the Miocene. This family is distinctive from other raptorial families for its highly mobile and variously elongated prothorax. Here, we describe several new genera and species from mid-Cretaceous Kachin amber, Myanmar: Three new species of Osmyloberotha Khramov, 2021 (O. dispersa sp. nov., O. chenzuyini Zhuo, Li & Liu sp. nov. and O. magnimaculata sp. nov.) in Berothidae, with a detailed redescription of O. simpla Khramov, 2021; two new genera and three new species (Paraberothinae: Paraberothoides longispina Li, Zhang & Liu gen. et sp. nov.; Subfamily unknown: Dicranoberotha zhangzhiqiae Zhuo, Li & Liu gen. et sp. nov., Dicranoberotha liumohanae Zhuo, Li & Liu gen. et sp. nov.) of Rhachiberothidae, three new species (Enigmadipteromantispa dilatata Li, Nakamine, Yamamoto & Liu sp. nov., Kurtodipteromantispa relicta Li, Nakamine, Yamamoto & Liu sp. nov. and Kurtodipteromantispa univenula sp. nov.) of Dipteromantispidae, as well as four new genera and five new species (Symphrasinae: Parvosymphrasites aploneura Li, Lin, Liu & Wang gen. et sp. nov. and Proplega evelynae Zhuo, Li & Liu gen. et sp. nov.; Subfamily unknown: Haplacantha robusta gen. et sp. nov., Haplacantha tenuis gen. et sp. nov. and Mesomantispoides felixoporcus gen. et sp. nov.) of Mantispidae. Sinuijumantispa So & Won, 2022, previously classified within Drepanicinae, is now recognized as a stem group of Mantispidae, which is possibly related to Mesomantispoides gen. nov. or Mesomantispinae. Our new findings offer crucial insights into the taxonomy, morphological diversity and evolution of Mantispoidea.

Ladybird beetles are high-mobility insects and explore broad areas by switching between walking and flying. Their excellent wing transformation systems enabling this lifestyle are expected to provide large potential for engineering applications. However, the mechanism behind the folding of their hindwings remains unclear. The reason is that ladybird beetles close the elytra ahead of wing folding, preventing the observation of detailed processes occurring under the elytra. In the present study, artificial transparent elytra were transplanted on living ladybird beetles, thereby enabling us to observe the detailed wing-folding processes. The result revealed that in addition to the abdominal movements mentioned in previous studies, the edge and ventral surface of the elytra, as well as characteristic shaped veins, play important roles in wing folding. The structures of the wing frames enabling this folding process and detailed 3D shape of the hindwing were investigated using microcomputed tomography. The results showed that the tape spring-like elastic frame plays an important role in the wing transformation mechanism. Compared with other beetles, hindwings in ladybird beetles are characterized by two seemingly incompatible properties: (i) the wing rigidity with relatively thick veins and (ii) the compactness in stored shapes with complex crease patterns. The detailed wing-folding process revealed in this study is expected to facilitate understanding of the naturally optimized system in this excellent deployable structure. Significance Hindwings in ladybird beetles successfully achieve compatibility between the deformability (instability) required for wing folding and strength property (stability) required for flying. This study demonstrates how ladybird beetles address these two conflicting requirements by an unprecedented technique using artificial wings. Our results, which clarify the detailed wing-folding process and reveal the supporting structures, provide indispensable initial knowledge for revealing this naturally evolved optimization system. Investigating the characteristics in the venations and crease patterns revealed in this study could provide an innovative designing method, enabling the integration of structural stability and deformability, and thus could have a considerable impact on engineering science.

Triassic fossils are rare but crucial for understanding the early evolution of large insect clades including beetles (Coleoptera). Their phylogenetic assignment is problematic because of fragmentary preservation, yet crucial for the correct use of the information they provide. Here an analysis is presented of the phylogenetic position of Leehermania prorova , the Late Triassic compressed fossil which was described and hitherto widely used as the oldest representative of Staphylinidae (rove beetles) in the suborder Polyphaga. By contrast with the intuitive character assessment made in the original description, a phylogenetic analysis of Leehermania is performed using an extensive morphological matrix of extant Coleoptera provided by the Beetle Tree of Life project, constrained in view of the latest relevant molecular phylogenies. As a result, Leehermania is identified as an extinct lineage within the beetle suborder Myxophaga, closest to the modern family Hydroscaphidae. Excluding Leehermania from Staphylinidae and placing it in Myxophaga amends erroneous assumptions about early diversification of rove beetles and enhances our views of the evolutionary history of Coleoptera.

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.