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Amber preserves an exceptional record of tiny, soft-bodied organisms and chemical environmental signatures, elucidating the evolution of arthropod lineages and the diversity, ecology, and biogeochemistry of ancient ecosystems. However, globally, fossiliferous amber deposits are rare in the latest Cretaceous and surrounding the Cretaceous-Paleogene (K-Pg) mass extinction. 1 , 2 , 3 , 4 , 5 This faunal gap limits our understanding of arthropod diversity and survival across the extinction boundary. 2 , 6 Contrasting hypotheses propose that arthropods were either relatively unaffected by the K-Pg extinction or experienced a steady decline in diversity before the extinction event followed by rapid diversification in the Cenozoic. 2 , 6 These hypotheses are primarily based on arthropod feeding traces on fossil leaves and time-calibrated molecular phylogenies, not direct observation of the fossil record. 2 , 7 Here, we report a diverse amber assemblage from the Late Cretaceous (67.04 ± 0.16 Ma) of the Big Muddy Badlands, Canada. The new deposit fills a critical 16-million-year gap in the arthropod fossil record spanning the K-Pg mass extinction. Seven arthropod orders and at least 11 insect families have been recovered, making the Big Muddy amber deposit the most diverse arthropod assemblage near the K-Pg extinction. Amber chemistry and stable isotopes suggest the amber was produced by coniferous (Cupressaceae) trees in a subtropical swamp near remnants of the Western Interior Seaway. The unexpected abundance of ants from extant families and the virtual absence of arthropods from common, exclusively Cretaceous families suggests that Big Muddy amber may represent a yet unsampled Late Cretaceous environment and provides evidence of a faunal transition before the end of the Cretaceous., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Female mosquitoes are among the most notorious blood-feeding insects, sometimes causing severe allergic responses or vectoring a variety of microbial pathogens. 1 , 2 The known Mesozoic Culicidae are Late Cretaceous, assigned to the modern Anophelinae or to the extinct Burmaculicinae, sister to other Culicidae, all with mouthparts of a modern type. Here, we report the discovery, in Lower Cretaceous amber from Lebanon, of two conspecific male mosquitoes unexpectedly with piercing mouthparts, armed with denticulate sharp mandibles and laciniae. These male fossils were likely hematophagous. They represent a lineage that diverged earlier than Burmaculicinae, extending the definitive occurrence of the family into the Early Cretaceous and serving to narrow the ghost-lineage gap for mosquitoes.3 , 4 particularly those of sufficient age, as to give insights into the paleoecological context in which blood feeding first appeared or even to arrive at gross estimates as to when such shifts have occurred. This is certainly the case for mosquitoes, a clade estimated molecularly to date back to the Jurassic. 5 The known Mesozoic Culicidae are Late Cretaceous, assigned to the modern Anophelinae or to the extinct Burmaculicinae, sister to other Culicidae, all with mouthparts of a modern type. Here, we report the discovery, in Lower Cretaceous amber from Lebanon, of two conspecific male mosquitoes unexpectedly with piercing mouthparts, armed with denticulate sharp mandibles and laciniae. These male fossils were likely hematophagous. They represent a lineage that diverged earlier than Burmaculicinae, extending the definitive occurrence of the family into the Early Cretaceous and serving to narrow the ghost-lineage gap for mosquitoes., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2023 Elsevier Inc. All rights reserved.)

Background: Phasmatodea (stick and leaf insects) play a central role on the debate regarding wing reduction and loss, and its wings are putative reacquisition from secondarily wingless ancestors based solely on extant species. A pivotal taxon in this respect is the species-poor Timematodea, consisting of approximately 21 wingless extant species, which form the sister group of all remaining winged or wingless stick and leaf insects, the Euphasmatodea., Results: Herein, the new fossils of Timematodea from mid-Cretaceous Kachin amber are reported, with winged and wingless species co-occurring. The palaeogeographic distributions of all fossils of Holophasmatodea are summarized, showing their wide paleo-distributions. The phylogenetic analysis based on morphological characters confirms the earliest-diverging lineage of winged Breviala cretacea gen. et sp. nov. in Timematodea, and the possible relationships among all families of Holophasmatodea. These are critical for the reconstruction of patterns of wing evolution in early Phasmatodea., Conclusions: The new fossils suggest that Timematodea once had wings, at least during the mid-Cretaceous. The palaeogeographic occurrences imply that Timematodea probably have been widely distributed since at least the Jurassic. The phylogenetic analysis with the ancestral-state reconstruction of wings indicates that the common ancestors of Holophasmatodea were winged, the reductions and losses of wings among Timematodea and Euphasmatodea have occurred independently since at least the Cretaceous, and the reduction or loss of the forewing earlier than the hind wings., (© 2023. BioMed Central Ltd., part of Springer Nature.)

We describe two new species of Lophocoronidae: Acanthocorona hedida Zhang, Shih and Engel sp. n. and Acanthocorona venulosa Zhang, Shih and Engel sp. n., and an undetermined specimen from mid-Cretaceous Kachin amber. Phylogenetic analysis of basal lepidopteran lineages, including three extinct families, was undertaken. The analysis supported monophyly of Glossata although internal relationships remain controversial. Acanthocorona and Lophocorona form a monophyletic group. It is likely that short and simply structured proboscides of Acanthocorona were used to sip water droplets, pollination drops from gymnosperms, nectar from early flowers, or sap from injured leaves. Both retracted and extended ovipositors are preserved in the material reported here, revealing their morphology and indicating that these Cretaceous lophocoronids inserted eggs into the tissues of their host plants., (© 2022 The Willi Hennig Society.)

This protocol explains how to extract pollen from fossil insects with subsequent descriptions of pollen treatment. We also describe how to document morphological and ultrastructural features with light-microscopy and electron microscopy. It enables a taxonomic assignment of pollen that can be used to interpret flower-insect interactions, foraging and feeding behavior of insects, and the paleoenvironment. The protocol is limited by the state of the fossil, the presence/absence of pollen on fossil specimens, and the availability of extant pollen for comparison. For complete details on the use and execution of this protocol, please refer to Wappler et al. (2015), Ulrich and Grímsson (2020), and Wedmann et al. (2021)., Competing Interests: The authors declare no competing interests., (© 2021 The Author(s).)

One of the most important trophic interactions today is that between insects and their floral hosts. This biotic association is believed to have been critical to the radiation of flowering plants and many pollinating insect lineages over the last 120 million years (Ma). Trophic interactions among fossil organisms are challenging to study, and most inferences are based on indirect evidence. Fossil records providing direct evidence for pollen feeding, i.e., fossil stomach and gut contents, are exceptionally rare. 1 , We analyzed the contents of the conspicuously swollen abdomen of an ca. 47.5 Ma old nemestrinid fly of the genus Hirmoneura from Messel, Germany, with photogrammetry and state-of-the-art palynological methods. The fly fed on pollen from at least four plant families-Lythraceae, Vitaceae, Sapotaceae, and Oleaceae-and presumably pollinated flowers of two extant genera, Decodon and Parthenocissus. We interpret the feeding and foraging behavior of the fly, reconstruct its preferred habitat, and conclude about its pollination role and importance in paratropical environments. This represents the first evidence that short-proboscid nemestrinid flies fed, and possibly feed to this day, on pollen, demonstrating how fossils can provide vital information on the behavior of insects and their ecological relationships with plants.2 Such records have the potential to provide information on aspects of animal behavior and ecology as well as plant-animal interactions that are sometimes not yet recognized for their extant relatives. The dietary preferences of short-proboscid nemestrinids are unknown, and pollinivory has not been recorded for extant Nemestrinidae. 3 We analyzed the contents of the conspicuously swollen abdomen of an ca. 47.5 Ma old nemestrinid fly of the genus Hirmoneura from Messel, Germany, with photogrammetry and state-of-the-art palynological methods. The fly fed on pollen from at least four plant families-Lythraceae, Vitaceae, Sapotaceae, and Oleaceae-and presumably pollinated flowers of two extant genera, Decodon and Parthenocissus. We interpret the feeding and foraging behavior of the fly, reconstruct its preferred habitat, and conclude about its pollination role and importance in paratropical environments. This represents the first evidence that short-proboscid nemestrinid flies fed, and possibly feed to this day, on pollen, demonstrating how fossils can provide vital information on the behavior of insects and their ecological relationships with plants., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Hadrosaurian dinosaurs were abundant in the Late Cretaceous of North America, but their habitats remain poorly understood. Cretaceous amber is also relatively abundant, yet it is seldom found in direct stratigraphic association with dinosaur remains. Here we describe an unusually large amber specimen attached to a Prosaurolophus jaw, which reveals details of the contemporaneous paleoforest and entomofauna. Fourier-transform Infrared spectroscopy and stable isotope composition (H and C) suggest the amber formed from resins exuded by cupressaceous conifers occupying a coastal plain. An aphid within the amber belongs to Cretamyzidae, a Cretaceous family suggested to bark-feed on conifers. Distinct tooth row impressions on the amber match the hadrosaur's alveolar bone ridges, providing some insight into the taphonomic processes that brought these remains together.

Jakub Prokop and Michael Engel introduce palaeodictyopterids, a very diverse extinct lineage of insects., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

The origin and early evolutionary history of polyphagan beetles have been largely based on evidence from the derived and diverse 'core Polyphaga', whereas little is known about the species-poor basal polyphagan lineages, which include Scirtoidea (Clambidae, Decliniidae, Eucinetidae, and Scirtidae) and Derodontidae. Here, we report two new species Acalyptomerus thayerae sp. nov. and Sphaerothorax uenoi sp. nov., both belonging to extant genera of Clambidae, from mid-Cretaceous Burmese amber. Acalyptomerus thayerae has a close affinity to A. herbertfranzi, a species currently occurring in Mesoamerica and northern South America. Sphaerothorax uenoi is closely related to extant species of Sphaerothorax, which are usually collected in forests of Nothofagus of Australia, Chile, and New Zealand. The discovery of two Cretaceous species from northern Myanmar indicates that both genera had lengthy evolutionary histories, originated at least by the earliest Cenomanian, and were probably more widespread than at present. Remarkable morphological similarities between fossil and living species suggest that both genera changed little over long periods of geological time. The long-term persistence of similar mesic microhabitats such as leaf litter may account for the 99 Myr morphological stasis in Acalyptomerus and Sphaerothorax. Additionally, the extinct staphylinoid family Ptismidae is proposed as a new synonym of Clambidae, and its only included species Ptisma zasukhae is placed as incertae sedis within Clambidae.

Cycads, unlike modern wind-pollinated conifers and Ginkgo, are unusual in that they are an ancient group of gymnosperms pollinated by insects [1-3]. Although it is well documented that cycads were diverse and abundant during the mid-Mesozoic, little is known about their biogeography and pollination before the rise of angiosperms. Direct fossil evidence illuminating the evolutionary history of cycads is extremely rare [4, 5]. Here we report a specialized beetle-mediated pollination mode from the mid-Cretaceous of Myanmar, wherein a new boganiid beetle, Cretoparacucujus cycadophilus, with specialized pollen-feeding adaptations in its mouthparts and legs, was associated with many pollen grains of Cycadopites. Phylogenetic analyses indicate Cretoparacucujus as a sister group to the extant Australian Paracucujus, which pollinate the cycad Macrozamia riedlei. Our discovery, along with the current disjunct distribution of related beetle-herbivore (tribe Paracucujini) and cycad-host (tribe Encephalarteae) pairs in South Africa and Australia, indicate a probable ancient origin of beetle pollination of cycads at least in the Early Jurassic, long before angiosperm dominance and the radiation of flowering-plant pollinators later in the Cretaceous., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Myrmeleontiformia are an ancient group of lacewing insects characterized by predatory larvae with unusual morphologies and behaviours. Mostly soil dwellers with a soft cuticle, their larvae fossilize only as amber inclusions, and thus their fossil record is remarkably sparse. Here, we document a disparate assemblage of myrmeleontiform larvae from the mid-Cretaceous amber (99 Ma) of Myanmar, evidence of a considerable diversification. Our cladistic analysis integrating extant and extinct taxa resolves the fossils as both stem- and crown-groups. Similarities between extinct and extant species permit inferences of larval ethology of the fossil species through statistical correlation analyses with high support, implying that morphological disparity matched behavioural diversity. An improved understanding of the evolutionary history of antlions and relatives supports the conclusion that hunting strategies, such as camouflage and fossoriality, were acquired early within the lineage.

The largest insects to have ever lived were the giant meganeurids of the Late Palaeozoic, ancient stem relatives of our modern dragonflies. With wingspans up to 71 cm, these iconic insects have been the subject of varied documentaries on Palaeozoic life, depicting them as patrolling for prey through coal swamp forests amid giant lycopsids, and cordaites. Such reconstructions are speculative as few definitive details of giant dragonfly biology are known. Most specimens of giant dragonflies are known from wings or isolated elements, but Meganeurites gracilipes preserves critical body structures, most notably those of the head. Here we show that it is unlikely it thrived in densely forested environments where its elongate wings would have become easily damaged. Instead, the species lived in more open habitats and possessed greatly enlarged compound eyes. These were dorsally hypertrophied, a specialization for long-distance vision above the animal in flight, a trait convergent with modern hawker dragonflies. Sturdy mandibles with acute teeth, strong spines on tibiae and tarsi, and a pronounced thoracic skewness are identical to those specializations used by dragonflies in capturing prey while in flight. The Palaeozoic Odonatoptera thus exhibited considerable morphological specializations associated with behaviours attributable to 'hawkers' or 'perchers' among extant Odonata.

Camouflage and mimicry are staples among predator-prey interactions, and evolutionary novelties in behavior, anatomy, and physiology that permit such mimesis are rife throughout the biological world [1, 2]. These specializations allow for prey to better evade capture or permit predators to more easily approach their prey, or in some cases, the mimesis can serve both purposes. Despite the importance of mimesis and camouflage in predator-avoidance or hunting strategies, the long-term history of these traits is often obscured by an insufficient fossil record. Here, we report the discovery of Upper Cretaceous (approximately 100 million years old) green lacewing larvae (Chrysopoidea), preserved in amber from northern Myanmar, anatomically modified to mimic coeval liverworts. Chrysopidae are a diverse lineage of lacewings whose larvae usually camouflage themselves with a uniquely constructed packet of exogenous debris, conveying greater stealth upon them as they hunt prey such as aphids as well as evade their own predators [3, 4]. However, no lacewing larvae today mimic their surroundings. While the anatomy of Phyllochrysa huangi gen. et sp. nov. allowed it to avoid detection, the lack of setae or other anatomical elements for entangling debris as camouflage means its sole defense was its mimicry, and it could have been a stealthy hunter like living and other fossil Chrysopoidea or been an ambush predator aided by its disguise. The present fossils demonstrate a hitherto unknown life-history strategy among these "wolf in sheep's clothing" predators, one that apparently evolved from a camouflaging ancestor but did not persist within the lineage., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Among the many challenges in paleobiology is the inference and reconstruction of behaviors that rarely, if ever, leave a physical trace on the environment that is suitable for fossilization. Of particular significance are those behaviors tied to mating and courtship, individual interactions critical for species integrity and continuance, as well as those for dispersal, permitting the taxon to expand its distribution as well as access new habitats in the face of local or long-term environmental change. In this context, two recently discovered fossils from the Early Cretaceous amber of Spain (ca. 105 mya) give a detailed view of otherwise fleeting ethologies in Collembola. These occurrences are phylogenetically spaced across the class, and from species representing the two major clades of springtails-Symphypleona and Entomobryomorpha. Specifically, we report unique evidence from a symphypleonan male (Pseudosminthurides stoechus Sánchez-García & Engel, 2016) with modified antennae that may have functioned as a clasping organ for securing females during mating on water's surface, and from an aggregation of entomobryomorphan individuals (Proisotoma communis Sánchez-García & Engel, 2016) purportedly representing a swarming episode on the forest floor. We demonstrate that the mating behavioral repertoire in P. stoechus, which is associated with considerable morphological adaptations, likely implied elaborate courtship and maneuvering for guarantee sperm transfer in an epineustic species. These discoveries reveal significant behaviors consistent with modern counterparts and a generalized stasis for some ancient hexapod ethologies associated with complex mating and courtship and social or pre-social aggregations, so critical to specific constancy and dispersal.

Parental care in animal evolution has long fascinated biologists, but tracing this complex of behavioural repertoires is challenging, as these transitory states often leave no corporeal traces as fossils. Among modern invertebrates, the tanaidaceans (Malacostraca: Peracarida), a lineage of marsupial crustaceans, show an interesting variety of brooding strategies. Here we report on fossil tanaidaceans from the Cretaceous of Spain and France that provide conclusive evidence for marsupial care of brood-offspring. Two exceptionally preserved female specimens of Alavatanais carabe and A. margulisae from Late Albian Peñacerrada I amber (Spain) possess four pairs of rudimentary oostegites, indicating formation of a marsupium. From Recent data, given the taxonomic distribution of a marsupium of four pairs of oostegites, we hypothesize that this may be plesiomorphic for the Tanaidomorpha. We also report on a peculiar tanaidacean specimen referable to the fossil family Alavatanaidae, Daenerytanais maieuticus gen. et sp. nov., from Early Cenomanian La Buzinie amber (France), preserved with its marsupial pouch and content. Our discoveries provide early evidence of the peracarid reproductive strategy, as seen in modern Tanaidacea, and argue that this form of parental care may have played a role in the diversification of the lineage during this period.

The appearance of wings in insects, early in their evolution [1], has been one of the more critical innovations contributing to their extraordinary diversity. Despite the conspicuousness and importance of wings, the origin of these structures has been difficult to resolve and represented one of the "abominable mysteries" in evolutionary biology [2]. More than a century of debate has boiled the matter down to two competing alternatives-one of wings representing an extension of the thoracic notum, the other stating that they are appendicular derivations from the lateral body wall. Recently, a dual model has been supported by genomic and developmental data [3-6], representing an amalgamation of elements from both the notal and pleural hypotheses. Here, we reveal crucial information from the wing pad joints of Carboniferous palaeodictyopteran insect nymphs using classical and high-tech techniques. These nymphs had three pairs of wing pads that were medially articulated to the thorax but also broadly contiguous with the notum anteriorly and posteriorly (details unobservable in modern insects), supporting their overall origin from the thoracic notum as well as the expected medial, pleural series of axillary sclerites. Our study provides support for the formation of the insect wing from the thoracic notum as well as the already known pleural elements of the arthropodan leg. These results support the unique, dual model for insect wing origins and the convergent reduction of notal fusion in more derived clades, presumably due to wing rotation during development, and they help to bring resolution to this long-standing debate., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Insecta s. str. (=Ectognatha), comprise the largest and most diversified group of living organisms, accounting for roughly half of the biodiversity on Earth. Understanding insect relationships and the specific time intervals for their episodes of radiation and extinction are critical to any comprehensive perspective on evolutionary events. Although some deeper nodes have been resolved congruently, the complete evolution of insects has remained obscure due to the lack of direct fossil evidence. Besides, various evolutionary phases of insects and the corresponding driving forces of diversification remain to be recognized. In this study, a comprehensive sample of all insect orders was used to reconstruct their phylogenetic relationships and estimate deep divergences. The phylogenetic relationships of insect orders were congruently recovered by Bayesian inference and maximum likelihood analyses. A complete timescale of divergences based on an uncorrelated log-normal relaxed clock model was established among all lineages of winged insects. The inferred timescale for various nodes are congruent with major historical events including the increase of atmospheric oxygen in the Late Silurian and earliest Devonian, the radiation of vascular plants in the Devonian, and with the available fossil record of the stem groups to various insect lineages in the Devonian and Carboniferous.

Background: Pterygota insects typically have symmetric veins in left and right wings. For studying taxonomy and phylogeny of fossil insects, venational patterns are commonly used as diagnostic characters, in conjunction with preserved body characters. Some examples of asymmetrical venation are known among extant insects, but only a few fossil insects with asymmetric wings have been reported, among which a previously described xyelotomid of Hymenoptera, Xyelocerus diaphanous, displays an unusual, small cell of vein Rs in the left forewing, but not in the right., Results: Herein we report a new sawfly of the family Xyelotomidae, Aethotoma aninomorpha gen. et sp. nov., from the late Middle Jurassic of China having a simple Sc in the forewing and Sc with two branches in the hind wing. In additional, the new specimen exhibits an enigmatic venational asymmetry. In the right forewing, crossvein 2r-rs of forms a loop, then forks into 2 long branches reaching Rs, while 2r-rs of the left forewing forks into 2 short branches reaching Rs, in contrast to a linear 2r-rs in typical fossil and extant sawflies., Conclusion: Such rare asymmetrical venation found from fossil sawflies provides a glance at early occurrences of venational variability and instability, or possibly aberrational development, for insects in the late Middle Jurassic.

Insects exhibit a wide diversity of anatomical specializations in their adult and immature stages associated with particular aspects of their biology. The order Neuroptera (lacewings, antlions, and their relatives) are a moderately diverse lineage of principally predatory animals, at least in their immature stages, as all have a modified piercing-sucking mandible-maxillary complex that allows them to drain fluids from their prey. As such, the larvae of various groups have evolved unique anatomical and behavioral specializations for approaching and subduing their prey, particularly the green lacewings (Chrysopidae), where immatures are also adept at camouflage [1-4]. Here we report the discovery of a unique mode of life among mid-Cretaceous mesochrysopids, an early stem group to modern green lacewings [5-7] exhibiting a combination of morphological modifications in both adults and larvae unknown among living and fossil Neuroptera, even across winged insects. The new mesochrysopids exhibit a uniquely prolonged thorax, elongate legs, and dramatically reduced hind wings in adults, and larvae have extremely elongate, slender legs with pectinate pretarsal claws and lacking trumpet-shaped empodia. The peculiarities of the larvae include features principally found in spider-associated insect groups, implying that these lacewings were early specialists on web-spinning spiders, either as active predators or kleptoparasites. This reveals a dramatic and ancient degree of ecological refinement in a major lineage of insect predators, for a food resource otherwise not utilized by most lacewings., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Ants comprise one lineage of the triumvirate of eusocial insects and experienced their early diversification within the Cretaceous [1-9]. Their ecological success is generally attributed to their remarkable social behavior. Not all ants cooperate in social hunting, however, and some of the most effective predatory ants are solitary hunters with powerful trap jaws [10]. Recent evolutionary studies predict that the early branching lineages of extant ants formed small colonies of ground-dwelling, solitary specialist predators [2, 5, 7, 11, 12], while some Cretaceous fossils suggest group recruitment and socially advanced behavior among stem-group ants [9]. We describe a trap-jaw ant from 99 million-year-old Burmese amber with head structures that presumably functioned as a highly specialized trap for large-bodied prey. These are a cephalic horn resulting from an extreme modification of the clypeus hitherto unseen among living and extinct ants and scythe-like mandibles that extend high above the head, both demonstrating the presence of exaggerated morphogenesis early among stem-group ants. The new ant belongs to the Haidomyrmecini, possibly the earliest ant lineage [9], and together these trap-jaw ants suggest that at least some of the earliest Formicidae were solitary specialist predators. With their peculiar adaptations, haidomyrmecines had a refined ecology shortly following the advent of ants., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

A fossil palpigrade is described and figured from mid-Cretaceous (Cenomanian) amber from northern Myanmar. Electrokoenenia yaksha Engel and Huang, gen. n. et sp. n., is the first Mesozoic fossil of its order and the only one known as an inclusion in amber, the only other fossil being a series of individuals encased in Pliocene onyx marble and 94-97 million years younger than E. yaksha. The genus is distinguished from other members of the order but is remarkably consistent in observable morphological details when compared to extant relatives, likely reflecting a consistent microhabitat and biological preferences over the last 100 million years.

With nearly 100,000 species, the Acercaria (lice, plant lices, thrips, bugs) including number of economically important species is one of the most successful insect lineages. However, its phylogeny and evolution of mouthparts among other issues remain debatable. Here new methods of preparation permitted the comprehensive anatomical description of insect inclusions from mid-Cretaceous Burmese amber in astonishing detail. These "missing links" fossils, attributed to a new order Permopsocida, provide crucial evidence for reconstructing the phylogenetic relationships in the Acercaria, supporting its monophyly, and questioning the position of Psocodea as sister group of holometabolans in the most recent phylogenomic study. Permopsocida resolves as sister group of Thripida + Hemiptera and represents an evolutionary link documenting the transition from chewing to piercing mouthparts in relation to suction feeding. Identification of gut contents as angiosperm pollen documents an ecological role of Permopsocida as early pollen feeders with relatively unspecialized mouthparts. This group existed for 185 million years, but has never been diverse and was superseded by new pollenivorous pollinators during the Cretaceous co-evolution of insects and flowers. The key innovation of suction feeding with piercing mouthparts is identified as main event that triggered the huge post-Carboniferous radiation of hemipterans, and facilitated the spreading of pathogenic vectors.

Amber holds special paleobiological significance due to its ability to preserve direct evidence of biotic interactions and animal behaviors for millions of years. Here we review the finding of Hallucinochrysa diogenesi Pérez-de la Fuente, Delclòs, Peñalver and Engel, 2012, a morphologically atypical larva related to modern green lacewings (Insecta: Neuroptera) that was described in Early Cretaceous amber from the El Soplao outcrop (northern Spain). The fossil larva is preserved with a dense cloud of fern trichomes that corresponds to the trash packet the insect gathered and carried on its back for camouflaging and shielding, similar to that which is done by its extant relatives. This finding supports the prominent role of wildfires in the paleoecosystem and provides direct evidence of both an ancient plant-insect interaction and an early acquisition of a defensive behavior in an insect lineage. Overall, the fossil of H. diogenesi showcases the potential that the amber record offers to reconstruct not only the morphology of fossil arthropods but, more remarkably, their lifestyles and ecological relationships., (Published by Elsevier Ltd.)

Bees (Anthophila) are one of the major groups of angiosperm-pollinating insects and accordingly are widely studied in both basic and applied research, for which it is essential to have a clear understanding of their phylogeny, and evolutionary history. Direct evidence of bee evolutionary history has been hindered by a dearth of available fossils needed to determine the timing and tempo of their diversification, as well as episodes of extinction. Here we describe four new compression fossils of bees from three different deposits (Miocene of la Cerdanya, Spain; Oligocene of Céreste, France; and Eocene of the Green River Formation, U.S.A.). We assess the similarity of the forewing shape of the new fossils with extant and fossil taxa using geometric morphometrics analyses. Predictive discriminant analyses show that three fossils share similar forewing shapes with the Apidae [one of uncertain tribal placement and perhaps near Euglossini, one definitive bumble bee (Bombini), and one digger bee (Anthophorini)], while one fossil is more similar to the Andrenidae. The corbiculate fossils are described as Euglossopteryx biesmeijeri De Meulemeester, Michez, & Engel, gen. nov. sp. nov. (type species of Euglossopteryx Dehon & Engel, n. gen.) and Bombus cerdanyensis Dehon, De Meulemeester, & Engel, sp. nov. They provide new information on the distribution and timing of particular corbiculate groups, most notably the extension into North America of possible Eocene-Oligocene cooling-induced extinctions. Protohabropoda pauli De Meulemeester & Michez, gen. nov. sp. nov. (type species of Protohabropoda Dehon & Engel, n. gen.) reinforces previous hypotheses of anthophorine evolution in terms of ecological shifts by the Oligocene from tropical to mesic or xeric habitats. Lastly, a new fossil of the Andreninae, Andrena antoinei Michez & De Meulemeester, sp. nov., further documents the presence of the today widespread genus Andrena Fabricius in the Late Oligocene of France.

Blood-feeding insects, as vectors of disease for humans and livestock alike, have garnered significant interest, but our understanding of their early evolution is hindered by the scarcity of available material and the difficulty in distinguishing early hematophages from non-blood-feeding relatives. Here, we report a new family of true bugs including two new genera and species from the Early Cretaceous Yixian Formation in Northeastern China. By utilizing geochemical methods for determining their diets and combining morphological and taphonomic data, we demonstrate that these new species represent the earliest evidence of blood feeding among true bugs, extending the geological record of such lineages by approximately 30 million years. Remarkably, one of the bugs appears to have perished immediately following a blood meal, which may have been from coexisting mammals, birds, or avian-related dinosaurs. These records expand the phylogenetic and ecological diversity of blood-feeding insects in the Early Cretaceous, enriching our knowledge of paleoecological associations in these ancient environments., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

Paleogene arthropod biotas have proved important for tracing the faunal turnover and intercontinental faunal interchange driven by climatic warming and geodynamic events [1-5]. Despite the large number of Paleogene fossil arthropods in Europe and North America [5-8], little is known about the typical Asian (Laurasia-originated) arthropod biota. Here, we report a unique amber biota (50-53 million years ago) from the Lower Eocene of Fushun in northeastern China, which fills a large biogeographic gap in Eurasia. Fushun amber is derived from cupressaceous trees, as determined by gas chromatography-mass spectrometry, infrared spectroscopy, and paleobotanical observations. Twenty-two orders and more than 80 families of arthropods have been reported so far, making it among the most diverse amber biotas. Our results reveal that an apparent radiation of ecological keystone insects, including eusocial, phytophagous, and parasitoid lineages, occurred at least during the Early Eocene Climatic Optimum. Some insect taxa have close phylogenetic affinities to those from coeval European ambers, showing a biotic interchange between the eastern and western margins of the Eurasian landmass during the Early Paleogene., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

The Eumetabola (Endopterygota (also known as Holometabola) plus Paraneoptera) have the highest number of species of any clade, and greatly contribute to animal species biodiversity. The palaeoecological circumstances that favoured their emergence and success remain an intriguing question. Recent molecular phylogenetic analyses have suggested a wide range of dates for the initial appearance of the Holometabola, from the Middle Devonian epoch (391 million years (Myr) ago) to the Late Pennsylvanian epoch (311 Myr ago), and Hemiptera (310 Myr ago). Palaeoenvironments greatly changed over these periods, with global cooling and increasing complexity of green forests. The Pennsylvanian-period crown-eumetabolan fossil record remains notably incomplete, particularly as several fossils have been erroneously considered to be stem Holometabola (Supplementary Information); the earliest definitive beetles are from the start of the Permian period. The emergence of the hymenopterids, sister group to other Holometabola, is dated between 350 and 309 Myr ago, incongruent with their current earliest record (Middle Triassic epoch). Here we describe five fossils--a Gzhelian-age stem coleopterid, a holometabolous larva of uncertain ordinal affinity, a stem hymenopterid, and early Hemiptera and Psocodea, all from the Moscovian age--and reveal a notable penecontemporaneous breadth of early eumetabolan insects. These discoveries are more congruent with current hypotheses of clade divergence. Eumetabola experienced episodes of diversification during the Bashkirian-Moscovian and the Kasimovian-Gzhelian ages. This cladogenetic activity is perhaps related to notable episodes of drying resulting from glaciations, leading to the eventual demise in Euramerica of coal-swamp ecosystems, evidenced by floral turnover during this interval. These ancient species were of very small size, living in the shadow of Palaeozoic-era 'giant' insects. Although these discoveries reveal unexpected Pennsylvanian eumetabolan diversity, the lineage radiated more successfully only after the mass extinctions at the end of the Permian period, giving rise to the familiar crown groups of their respective clades.

Marden's (2013) reanalysis of Knecht et al. (2011) suggesting that specimen SEMC-F97 is the result of the skimming behavior of a neopteran insect and, more importantly, fossil evidence of "… surface skimming as a precursor to the evolution of flight in insects" (Marden 2013) is found to be deficient on three fronts: (1) the principal specimen was never viewed firsthand which led to significant morphological misinterpretations; (2) poorly designed and executed neoichnological experiments led to incredulous results; and (3) the assumption that this specimen is fossil evidence supporting the surface skimming hypothesis of the origin of insect flight despite the fact that since its induction into the literature that hypothesis has been refuted based on significant paleontological, phylogenetic, genetic, and developmental evidence., (© 2013 The Author(s). Evolution © 2013 The Society for the Study of Evolution.)

The species of the Strashilidae (strashilids) have been the most perplexing of fossil insects from the Jurassic period of Russia and China. They have been widely considered to be ectoparasites of pterosaurs or feathered dinosaurs, based on the putative presence of piercing and sucking mouthparts and hind tibio-basitarsal pincers purportedly used to fix onto the host's hairs or feathers. Both the supposed host and parasite occur in the Daohugou beds from the Middle Jurassic epoch of China (approximately 165 million years ago). Here we analyse the morphology of strashilids from the Daohugou beds, and reach markedly different conclusions; namely that strashilids are highly specialized flies (Diptera) bearing large membranous wings, with substantial sexual dimorphism of the hind legs and abdominal extensions. The idea that they belong to an extinct order is unsupported, and the lineage can be placed within the true flies. In terms of major morphological and inferred behavioural features, strashilids resemble the recent (extant) and relict members of the aquatic fly family Nymphomyiidae. Their ontogeny are distinguished by the persistence in adult males of larval abdominal respiratory gills, representing a unique case of paedomorphism among endopterygote insects. Adult strashilids were probably aquatic or amphibious, shedding their wings after emergence and mating in the water.

After terrestrialization, the diversification of arthropods and vertebrates is thought to have occurred in two distinct phases, the first between the Silurian and the Frasnian stages (Late Devonian period) (425-385 million years (Myr) ago), and the second characterized by the emergence of numerous new major taxa, during the Late Carboniferous period (after 345 Myr ago). These two diversification periods bracket the depauperate vertebrate Romer's gap (360-345 Myr ago) and arthropod gap (385-325 Myr ago), which could be due to preservational artefact. Although a recent molecular dating has given an age of 390 Myr for the Holometabola, the record of hexapods during the Early-Middle Devonian (411.5-391 Myr ago, Pragian to Givetian stages) is exceptionally sparse and based on fragmentary remains, which hinders the timing of this diversification. Indeed, although Devonian Archaeognatha are problematic, the Pragian of Scotland has given some Collembola and the incomplete insect Rhyniognatha, with its diagnostic dicondylic, metapterygotan mandibles. The oldest, definitively winged insects are from the Serpukhovian stage (latest Early Carboniferous period). Here we report the first complete Late Devonian insect, which was probably a terrestrial species. Its 'orthopteroid' mandibles are of an omnivorous type, clearly not modified for a solely carnivorous diet. This discovery narrows the 45-Myr gap in the fossil record of Hexapoda, and demonstrates further a first Devonian phase of diversification for the Hexapoda, as in vertebrates, and suggests that the Pterygota diversified before and during Romer's gap.

Fleas are one of the major lineages of ectoparasitic insects and are now highly specialized for feeding on the blood of birds or mammals. This has isolated them among holometabolan insect orders, although they derive from the Antliophora (scorpionflies and true flies). Like most ectoparasitic lineages, their fossil record is meagre and confined to Cenozoic-era representatives of modern families, so that we lack evidence of the origins of fleas in the Mesozoic era. The origins of the first recognized Cretaceous stem-group flea, Tarwinia, remains highly controversial. Here we report fossils of the oldest definitive fleas--giant forms from the Middle Jurassic and Early Cretaceous periods of China. They exhibit many defining features of fleas but retain primitive traits such as non-jumping hindlegs. More importantly, all have stout and elongate sucking siphons for piercing the hides of their hosts, implying that these fleas may be rooted among the pollinating 'long siphonate' scorpionflies of the Mesozoic. Their special morphology suggests that their earliest hosts were hairy or feathered 'reptilians', and that they radiated to mammalian and bird hosts later in the Cenozoic.

Despite centuries of research addressing amber and its various inclusions, relatively little is known about the specific events having stimulated the production of geologically relevant volumes of plant resin, ultimately yielding amber deposits. Although numerous hypotheses have invoked the role of insects, to date these have proven difficult to test. Here, we use the current mountain pine beetle outbreak in western Canada as an analogy for the effects of infestation on the stable isotopic composition of carbon in resins. We show that infestation results in a rapid (approx. 1 year) (13)C enrichment of fresh lodgepole pine resins, in a pattern directly comparable with that observed in resins collected from uninfested trees subjected to water stress. Furthermore, resin isotopic values are shown to track both the progression of infestation and instances of recovery. These findings can be extended to fossil resins, including Miocene amber from the Dominican Republic and Late Cretaceous New Jersey amber, revealing similar carbon-isotopic patterns between visually clean ambers and those associated with the attack of wood-boring insects. Plant exudate δ(13)C values constitute a sensitive monitor of ecological stress in both modern and ancient forest ecosystems, and provide considerable insight concerning the genesis of amber in the geological record.

Insects were the first animals to evolve powered flight and did so perhaps 90 million years before the first flight among vertebrates. However, the earliest fossil record of flying insect lineages (Pterygota) is poor, with scant indirect evidence from the Devonian and a nearly complete dearth of material from the Early Carboniferous. By the Late Carboniferous a diversity of flying lineages is known, mostly from isolated wings but without true insights into the paleoethology of these taxa. Here, we report evidence of a full-body impression of a flying insect from the Late Carboniferous Wamsutta Formation of Massachusetts, representing the oldest trace fossil of Pterygota. Through ethological and morphological analysis, the trace fossil provides evidence that its maker was a flying insect and probably was representative of a stem-group lineage of mayflies. The nature of this current full-body impression somewhat blurs distinctions between the systematics of traces and trace makers, thus adding to the debate surrounding ichnotaxonomy for traces with well-associated trace makers.

For nearly 100 million years, the India subcontinent drifted from Gondwana until its collision with Asia some 50 Ma, during which time the landmass presumably evolved a highly endemic biota. Recent excavations of rich outcrops of 50-52-million-year-old amber with diverse inclusions from the Cambay Shale of Gujarat, western India address this issue. Cambay amber occurs in lignitic and muddy sediments concentrated by near-shore chenier systems; its chemistry and the anatomy of associated fossil wood indicates a definitive source of Dipterocarpaceae. The amber is very partially polymerized and readily dissolves in organic solvents, thus allowing extraction of whole insects whose cuticle retains microscopic fidelity. Fourteen orders and more than 55 families and 100 species of arthropod inclusions have been discovered thus far, which have affinities to taxa from the Eocene of northern Europe, to the Recent of Australasia, and the Miocene to Recent of tropical America. Thus, India just prior to or immediately following contact shows little biological insularity. A significant diversity of eusocial insects are fossilized, including corbiculate bees, rhinotermitid termites, and modern subfamilies of ants (Formicidae), groups that apparently radiated during the contemporaneous Early Eocene Climatic Optimum or just prior to it during the Paleocene-Eocene Thermal Maximum. Cambay amber preserves a uniquely diverse and early biota of a modern-type of broad-leaf tropical forest, revealing 50 Ma of stasis and change in biological communities of the dipterocarp primary forests that dominate southeastern Asia today.

Among insects, eusocial behavior occurs in termites, ants, some bees and wasps. Isoptera and Hymenoptera convergently share social behavior, and for both taxa its evolution remains poorly understood. While dating analyses provide researchers with the opportunity to date the origin of eusociality, fossil calibration methodology may mislead subsequent ecological interpretations. Using a comprehensive termite dataset, we explored the effect of fossil placement and calibration methodology. A combined molecular and morphological dataset for 42 extant termite lineages was used, and a second dataset including these 42 taxa, plus an additional 39 fossil lineages for which we had only morphological data. MrBayes doublet-model analyses recovered similar topologies, with one minor exception (Stolotermitidae is sister to the Hodotermitidae, s.s., in the 42-taxon analysis but is in a polytomy with Hodotermitidae and (Kalotermitidae + Neoisoptera) in the 81-taxon analysis). Analyses using the r8s program on these topologies were run with either minimum/maximum constraints (analysis a = 42-taxon and analysis c = 81-taxon analyses) or with the fossil taxon ages fixed (ages fixed to be the geological age of the deposit from which they came, analysis b = 81-taxon analysis). Confidence intervals were determined for the resulting ultrametric trees, and for most major clades there was significant overlap between dates recovered for analyses A and C (with exceptions, such as the nodes Neoisoptera, and Euisoptera). With the exception of isopteran and eusiopteran node ages, however, none of the major clade ages overlapped when analysis B is compared with either analysis A or C. Future studies on Dictyoptera should note that the age of Kalotermitidae was underestimated in absence of kalotermitid fossils with fixed ages., (Copyright (c) 2009 Elsevier Ltd. All rights reserved.)

Aside from pollen and nectar, bees of the subfamily Megachilinae are closely associated with plants as a source of materials for nest construction. Megachilines use resins, masticated leaves, trichomes and other plant materials sometimes along with mud to construct nests in cavities or in soil. Among these, the leafcutter bees (Megachile s.l.) are the most famous for their behaviour to line their brood cells with discs cut from various plants. We report on fossil records of one body fossil of a new non-leafcutting megachiline and of 12 leafcuttings from three European sites-Eckfeld and Messel, both in Germany (Eocene), and Menat, France (Paleocene). The excisions include the currently earliest record of probable Megachile activity and suggest the presence of such bees in the Paleocene European fauna. Comparison with extant leafcuttings permits the interpretation of a minimal number of species that produced these excisions. The wide range of size for the leafcuttings indirectly might suggest at least two species of Megachile for the fauna of Messel in addition to the other megachiline bee described here. The presence of several cuttings on most leaves from Eckfeld implies that the preferential foraging behaviour of extant Megachile arose early in megachiline evolution. These results demonstrate that combined investigation of body and trace fossils complement each other in understanding past biodiversity, the latter permitting the detection of taxa not otherwise directly sampled and inferences on behavioural evolution.

Fossilized, winged adults belonging to the psocopteran family Liposcelididae are reported in amber from the mid-Cretaceous (ca 100 Myr) of Myanmar (described as Cretoscelis burmitica, gen. et sp. n.) and the Miocene (ca 20 Myr) of the Dominican Republic (Belaphopsocus dominicus sp. n.). Cretoscelis is an extinct sister group to all other Liposcelididae and the family is the free-living sister group to the true lice (order Phthiraptera, all of which are ectoparasites of birds and mammals). A phylogenetic hypothesis of relationships among genera of Liposcelididae, including fossils, reveals perfect correspondence between the chronology of fossils and cladistic rank of taxa. Lice and Liposcelididae minimally diverged 100 Myr, perhaps even in the earliest Cretaceous 145 Myr or earlier, in which case the hosts of lice would have been early mammals, early birds and possibly other feathered theropod dinosaurs, as well as haired pterosaurs.

Insects are the most diverse lineage of all life in numbers of species, and ecologically they dominate terrestrial ecosystems. However, how and when this immense radiation of animals originated is unclear. Only a few fossils provide insight into the earliest stages of insect evolution, and among them are specimens in chert from Rhynie, Scotland's Old Red Sandstone (Pragian; about 396-407 million years ago), which is only slightly younger than formations harbouring the earliest terrestrial faunas. The most well-known animal from Rhynie is the springtail Rhyniella praecursor (Entognatha; Collembola), long considered to be the oldest hexapod. For true insects (Ectognatha), the oldest records are two apparent wingless insects from later in the Devonian period of North America. Here we show, however, that a fragmentary fossil from Rhynie, Rhyniognatha hirsti, is not only the earliest true insect but may be relatively derived within basal Ectognatha. In fact, Rhyniognatha has derived characters shared with winged insects, suggesting that the origin of wings may have been earlier than previously believed. Regardless, Rhyniognatha indicates that insects originated in the Silurian period and were members of some of the earliest terrestrial faunas.

Fossils encompassing multiple individuals provide rare direct evidence of behavioral interactions among extinct organisms. However, the fossilization process can alter the spatial relationship between individuals and hinder behavioral reconstruction. Here, we report a Baltic amber inclusion preserving a female-male pair of the extinct termite species Electrotermes affinis. The head-to-abdomen contact in the fossilized pair resembles the tandem courtship behavior of extant termites, although their parallel body alignment differs from the linear alignment typical of tandem runs. To solve this inconsistency, we simulated the first stage of amber formation, the immobilization of captured organisms, by exposing living termite tandems to sticky surfaces. We found that the posture of the fossilized pair matches trapped tandems and differs from untrapped tandems. Thus, the fossilized pair likely is a tandem running pair, representing the direct evidence of the mating behavior of extinct termites. Furthermore, by comparing the postures of partners on a sticky surface and in the amber inclusion, we estimated that the male likely performed the leader role in the fossilized tandem. Our results demonstrate that past behavioral interactions can be reconstructed despite the spatial distortion of body poses during fossilization. Our taphonomic approach demonstrates how certain behaviors can be inferred from fossil occurrences. [ABSTRACT FROM AUTHOR]

Clubtail dragonfly Lindenia heeri sp. nov., is described and figured as the first fossil representative of the extant lindeniine genus Lindenia, based on a finely preserved forewing from the mid-Miocene lacustrine maar of Öhningen, Germany. The new species differs from the type and only species of Lindenia tetraphylla in the dark brown pterostigma covering ten cells vs. only five. Otherwise its forewing venation is identical to that of the modern species. The paleoclimatic data fit well with the climatic preferences of extant Lindenia tetraphylla, consistent with the generally warmer climate of that region during that period of time, allowing for more Mediterranean or even subtropical elements of the flora and fauna to persist. [ABSTRACT FROM AUTHOR]