Stem chewing lice on Cretaceous feathers preserved in amber.

Phthirapteran lice (true lice or parasitic lice) are a major group of ectoparasitic insects living on their bird or mammal hosts during their entire life cycle.1 Due to their highly specialized lifestyles, they are extremely poorly represented in fossil records.2 Molecular clock estimations have speculated extensively about the origin time of parasitic lice,3,4 yet none have been confirmed unequivocally. Herein, we report a new family of stem chewing lice, based on two adult insects associated with several semiplume feathers preserved within a piece of Kachin amber from the mid-Cretaceous. They display some defining characteristics of the Amblycera, an early-diverging lineage of the crown lice group. These features include a wingless body, chewing mouthparts, narrow and small thorax, and short tarsus with elongated euplantulae. Our phylogenetic analysis places the new taxa in the Amblycera, and the discovery thus pushes back the lice fossil records by at least 55 million years. Furthermore, the new specimens show primitive characters such as compressed and club-shaped terminal segments of antennae, maxillary and labial palps, and unmodified femora of hind legs, providing key information for the evolutionary relationship between free-living booklice and parasitic lice. This suggests that some ectoparasitic characters defining the crown lice group might have evolved among amblyceran and non-amblyceran lice in parallel. These newly described fossil specimens imply at least a Cretaceous age of Phthiraptera.

Independent wing reductions and losses among stick and leaf insects (Phasmatodea), supported by new Cretaceous fossils in amber.

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.

Early specializations for mimicry and defense in a Jurassic stick insect.

Mimicry and secondary defense are staples among predator-prey interactions. Among insects, the stick and leaf insects are masters of camouflage. Nonetheless, a meager understanding of their origin and early mimetic evolution persists. Here, we report the earliest mimetic and defensive strategies of a stick insect from the Middle Jurassic of China, Aclistophasma echinulatum gen. et sp. nov., exquisitely preserving abdominal extensions and femoral spines. The distribution of these characteristics mapped onto the phylogeny of Phasmatodea reveals that abdominal extensions and femoral spines developed multiple times during the evolution of stick insects, and indicates that the origin of abdominal extensions predates other modifications, while tergal extensions predate other expansions of the body, such as those of the sterna and pleura, as well as defensive femoral spines. The new fossil provides clues into early antipredator defensive strategies, allows inferences as to the potential environment and predators, and reveals the mimetic and defensive mechanisms of stick insects from 165 million years ago.

The first queen-worker association for Cretaceous Formicidae: the winged caste of Haidomyrmex cerberus.

Two queen ant specimens, one alate and one dealate, from mid-Cretaceous (Late Albian-Early Cenomanian) Burmese amber are herein reported as belonging Haidomyrmex cerberus Dlussky, 1996. This is the first discovery and documentation of an alate queen in Haidomyrmex. Compared with workers of Haidomyrmex cerberus, alate and dealate queens are larger in body size, have smaller compound eyes, a longer antennal scape, more complex mandibles, and a relatively large-sized metasoma. It is hypothesized that these differences are due to caste differences.

The mid-Miocene Zhangpu biota reveals an outstandingly rich rainforest biome in East Asia.

During the Mid-Miocene Climatic Optimum [MMCO, ~14 to 17 million years (Ma) ago], global temperatures were similar to predicted temperatures for the coming century. Limited megathermal paleoclimatic and fossil data are known from this period, despite its potential as an analog for future climate conditions. Here, we report a rich middle Miocene rainforest biome, the Zhangpu biota (~14.7 Ma ago), based on material preserved in amber and associated sedimentary rocks from southeastern China. The record shows that the mid-Miocene rainforest reached at least 24.2°N and was more widespread than previously estimated. Our results not only highlight the role of tropical rainforests acting as evolutionary museums for biodiversity at the generic level but also suggest that the MMCO probably strongly shaped the East Asian biota via the northern expansion of the megathermal rainforest biome. The Zhangpu biota provides an ideal snapshot for biodiversity redistribution during global warming.

Jurassic scorpionflies (Mecoptera) with swollen first metatarsal segments suggesting sexual dimorphism.

BACKGROUND: Sexual dimorphism is widespread in insects. The certain specialized structures may be used as weapons in male-male combats or as ornaments to enhance mating opportunities. RESULTS: We report striking swollen first tarsal segments in two families, four genera and six species of scorpionflies from the Middle Jurassic Yanliao Biota of Northeastern China. Swollen tarsal segments are restricted to male specimens and to hind leg tarsi. The geometric morphometric analyses reveal that the degree of swelling within the orthophlebiid species possessing swollen first metatarsal segments is species-specific, which can be used as a diagnostic character for taxonomic and phylogenetic studies. CONCLUSIONS: The new findings indicate that swollen first metatarsal segments are relatively common in the family Orthophlebiidae during the Middle Jurassic. The tarsal swellings are considered to be sexually dimorphic, potentially associated with sexually display by males and/or camouflage of a "nuptial gift" in the mating process.

Behaviors and Interactions of Insects in Mid-Mesozoic Ecosystems of Northeastern China.

During the past 20 years, more than 1,600 species of well-preserved fossil insects, including members of over 270 families within 24 orders, have been described from the Middle Jurassic Yanliao Entomofauna and Early Cretaceous Jehol Entomofauna in Northeastern China. Diversified fossil insects not only document the origin, systematics, and early evolution of many lineages, but also reveal these lineages' behaviors and interactions with coexisting plants, vertebrates, and other insects in their ecosystems. Fossil evidence has been documented, for example, regarding insects' feeding and pollination mutualism with gymnosperms; ectoparasitic feeding on blood of vertebrates; camouflage, mimicry of gymnosperm plants, and eyespot warning; sound stridulation for attracting potential mates; and sexual display, mating, egg-laying, and parental care. In this article, we review the diverse taxonomy of mid-Mesozoic insects of Northeastern China and elucidate their behaviors and interactions within their ecosystems, which have impacted their early evolution and development into extant insects.

A new species of Astreptolabis in mid-Cretaceous amber from northern Myanmar, with the discovery of the first male of Astreptolabidinae (Dermaptera).

A new species of one of the basal families among extant Dermaptera, Pygidicranidae, is described from mid-Cretaceous amber of Myanmar based on two females and a male. Astreptolabis laevis sp. nov., belongs to the extinct subfamily Astreptolabidinae, sharing the diagnostic combination of features typical of this group, such as the well-developed compound eyes, large pronotum, and straight and tubular cerci. The discovery of a male with its genitalia partly exerted permits characterization of traits for the subfamily and provides further information on the uniqueness and affinities of the subfamily. In addition, the extended hind wing allows for a comparison between the folding mechanism between these fossils and their modern counterparts, demonstrating considerable conservatism in hind wing evolution among Dermaptera.

Termite colonies from mid-Cretaceous Myanmar demonstrate their early eusocial lifestyle in damp wood.

Insect eusociality is characterized by cooperative brood care, reproductive division of labour and multiple generations of adults within a colony. The morphological specializations of the different termite castes from Burmese amber were recently reported, indicating the termites possessed advanced sociality in the mid-Cretaceous. Unfortunately, all the reported Cretaceous termites are individually preserved, which does not cover the behaviours of the cooperative brood care and multiple generations of adults in the nests of the Cretaceous termites. Herein, we report three eusocial aggregations from colonies of the oldest known Stolotermitidae, Cosmotermes gen. nov., in 100 Ma mid-Cretaceous Burmese amber. One large aggregation, comprising 8 soldiers, 56 workers/pseudergates and 25 immatures of different instars, additionally presents the behaviours of cooperative brood care and overlapping generations. Furthermore, taphonomic evidence indicates Cosmotermes most probably dwelled in damp/rotting wood, which provides a broader horizon of the early societies and ecology of the eusocial Cosmotermes.

A new sawfly of Megalodontesidae (Insecta, Hymenoptera, Pamphilioidea) with pectinate antennae from the Early Cretaceous of China.

A new sawfly of Megalodontesidae, Jibaissodes peichenae sp. nov., is described from the Lower Cretaceous Yixian Formation of Northeastern China. It is established mainly based on the pectinate antenna comprising 42 flagellomeres and the proximal 28 bearing apical rami, which gradually shorten in length toward the apex of the flagellum. The pterostigma of the forewing is infuscated apically and on the hind wing, vein 1-Rs is nearly equal to 1r-m and slightly shorter than 1-M. The first tergum is widely excised posteriorly and roundly protruding laterally alike in Megalodontes. This find supports that pectinate antennae in extant sawflies of Megalodontesidae originated at least during or before the Early Cretaceous.

New insects feeding on dinosaur feathers in mid-Cretaceous amber.

Due to a lack of Mesozoic fossil records, the origins and early evolution of feather-feeding behaviors by insects are obscure. Here, we report ten nymph specimens of a new lineage of insect, Mesophthirus engeli gen et. sp. nov. within Mesophthiridae fam. nov. from the mid-Cretaceous (ca. 100 Mya) Myanmar (Burmese) amber. This new insect clade shows a series of ectoparasitic morphological characters such as tiny wingless body, head with strong chewing mouthparts, robust and short antennae having long setae, legs with only one single tarsal claw associated with two additional long setae, etc. Most significantly, these insects are preserved with partially damaged dinosaur feathers, the damage of which was probably made by these insects' integument-feeding behaviors. This finding demonstrates that feather-feeding behaviors of insects originated at least in mid-Cretaceous, accompanying the radiation of feathered dinosaurs including early birds.

Cretaceous winged stick insects clarify the early evolution of Phasmatodea.

Wingless and shorter winged stick insects are very common today, but most known extinct stick insects had fully developed wings, leading to contentious affinities among the extinct winged and extant groups. We report herein three male winged stick insects, assigned to Pterophasmatidae fam. nov., from mid-Cretaceous Myanmar (Burmese) amber. Pterophasmatidae fam. nov. are regarded as transitional taxa from extinct winged to modern wingless and shorter winged stick insects based on their similar tegmina venation with extinct Susumanioidea and some body features the same as extant Phasmatodea. However, their symmetric phallic organs comprising two consistent phallomeres are different from those of all living groups. Phylogenetic analyses suggest that the extinct winged taxa, including the new family, are the stem groups of modern stick and leaf insects, and all of them constitute the clade of Phasmatodea. New findings indicate winged and wingless stick insects' morphologies diversified significantly during or before the mid-Cretaceous.

The earliest Timematids in Burmese amber reveal diverse tarsal pads of stick insects in the mid-Cretaceous.

Many extant insects have developed pad structures, euplantulae or arolia on their tarsi to increase friction or enhance adhesion for better mobility. Many polyneopteran insects with euplantulae, for example, Grylloblattodea, Mantophasmatodea and Orthoptera, have been described from the Mesozoic. However, the origin and evolution of stick insects' euplantulae are poorly understood due to rare fossil records. Here, we report the earliest fossil records of Timematodea hitherto, Tumefactipes prolongates gen. et sp. nov. and Granosicorpes lirates gen. et sp. nov., based on three specimens from mid-Cretaceous Burmese amber. Specimens of Tumefactipes prolongates gen. et sp. nov. have extremely specialized and expanded euplantulae on their tarsomere II. These new findings are the first known and the earliest fossil records about euplantula structure within Phasmatodea, demonstrating the diversity of euplantulae in Polyneoptera during the Mesozoic. Such tarsal pads might have increased friction and helped these mid-Cretaceous stick insects to climb more firmly on various surfaces, such as broad leaves, wetted tree branches or ground. These specimens provide more morphological data for us to understand the relationships of Timematodea, Euphasmatodea, Orthoptera and Embioptera, suggesting that Timematodea might be monophyletic with Euphasmatodea rather than Embioptera and Phasmatodea should have a closer relationship with Orthoptera rather than Embioptera.

Stick insect in Burmese amber reveals an early evolution of lateral lamellae in the Mesozoic.

Extant stick and leaf insects commonly imitate twigs or leaves, with lateral lamellae used to enhance crypsis or achieve mimicry for protection. However, the origin and early evolution of such lateral expansions among Phasmatodea are unknown, because all known Mesozoic phasmatodeans hitherto lack preserved evidence of such structures. We report here the first Mesozoic stick insect, Elasmophasma stictum gen. et sp. nov., with well-preserved, thin, lateral lamellae on the thoracic pleura, the terga of abdominal segments I-X and the ventrolateral margins of all femora. This new species, from the mid-Cretaceous amber of northern Myanmar, has a clear, stick-like body and is assigned to Euphasmatodea. The abdominal structures of E. stictum exhibit traces of multiple expansions of the terga, suggesting that such structure might have been an early development of body expansions used to improve crypsis for stick or leaf insects when they sprawled on twigs or leaves.

Convergent evolution of ramified antennae in insect lineages from the Early Cretaceous of Northeastern China.

Antennae are important, insect sensory organs that are used principally for communication with other insects and the detection of environmental cues. Some insects independently evolved ramified (branched) antennae, which house several types of sensilla for motion detection, sensing olfactory and chemical cues, and determining humidity and temperature levels. Though ramified antennae are common in living insects, occasionally they are present in the Mesozoic fossil record. Here, we present the first caddisflies with ramified antennae, the earliest known fossil sawfly, and a scorpionfly also with ramified antennae from the mid-Lower Cretaceous Yixian Formation of Northeastern China, dated at 125 million years ago (Ma). These three insect taxa with ramified antennae consist of three unrelated lineages and provide evidence for broad structural convergence that historically has been best demonstrated by features such as convergent mouthparts. In addition, ramified antennae in these Mid-Mesozoic lineages likely do not constitute a key innovation, as they are not associated with significantly increased diversification compared with closely related lineages lacking this trait, and nor are they ecologically isolated from numerous, co-occurring insect species with unmodified antennae.

A new xyelotomid (Hymenoptera) from the Middle Jurassic of China displaying enigmatic venational asymmetry.

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.

The first flea with fully distended abdomen from the Early Cretaceous of China.

BACKGROUND: Fleas, the most notorious insect ectoparasites of human, dogs, cats, birds, etc., have recently been traced to its basal and primitive ancestors during the Middle Jurassic. Compared with extant fleas, these large basal fleas have many different features. Although several fossil species with transitional morphologies filled the evolutionary blank, the early evolution of these ectoparasites is still poorly known. RESULTS: Here we report a new flea with transitional characters, Pseudopulex tanlan sp. nov., assigned to Pseudopulicidae, from the Lower Cretaceous Yixian Formation of Liaoning Province, China. Different from the previously described pseudopulicids, P. tanlan has relatively smaller body size but lacking any ctenidia on the tibiae or body, while the male with comparatively smaller and shorter genitalia. On the other hand, P. tanlan has some characters similar to the transitional fleas of saurophthirids, such as, a small head, short compacted antennae, small pygidium and many stiff setae covering the body. CONCLUSIONS: Even though other possibilities can not be ruled out, the female specimen with extremely distended abdomen suggests that it might have consumed its last meal before its demise. Compared with other reported female flea fossils, we calculate and estimate that P. tanlan sp. nov. might have consumed 0.02 milliliter (ml) of blood, which is about 15 times of the intake volume by extant fleas. These new findings further support that fleas had evolved a broad diversity by the Early Cretaceous.

A catalytic asymmetric hetero-Diels-Alder reaction of olefinic azlactones and isatins: facile access to chiral spirooxindole dihydropyranones.

A catalytic asymmetric hetero-Diels-Alder (HDA) reaction has been achieved through hydrogen-bond directed γ-addition of olefinic azlactones to isatins. This methodology provides an efficient access to spirooxindole dihydropyranones in moderate to good yields and with excellent enantioselectivities.