A comparison of dissection and 3D approaches to estimate muscle physiological cross-sectional area, validated by in vivo bite forces.

Performance traits such as bite forces are crucial to fitness and relate to the niche and adaptation of species. However, for many insects it is not possible to directly measure bite forces because they are too small. Biomechanical models of bite forces are therefore relevant to test hypotheses of adaptation in insects and other small organisms. Although such models are based on classical mechanics, combining forces, material properties and laws of levers, it is currently unknown how various models relate to bite forces measured in vivo. One critical component of these models is the physiological cross-sectional area (PCSA) of muscles, which relates to the maximum amount of force they can produce. Here, using the grasshopper Schistocerca gregaria, we compare various ways to obtain PCSA values and use in vivo measurements of bite forces to validate the biomechanical models. We show that most approaches used to derive PCSA (dissection, 3D muscle convex hull volume, muscle attachment area) are consistent with the expected relationships between PCSA and bite force, as well as with the muscle stress values known for insects. The only exception to this are PCSA values estimated by direct 3D muscle volume computation, which could be explained by noisy variation produced by shrinkage. This method therefore produces PCSA values which are uncorrelated to in vivo bite forces. Furthermore, despite the fact that all other methods do not significantly differ from expectations, their derived PCSA values vary widely, suggesting a lack of comparability between studies relying on different methods.

Neuromodulation Can Be Simple: Myoinhibitory Peptide, Contained in Dedicated Regulatory Pathways, Is the Only Neurally-Mediated Peptide Modulator of Stick Insect Leg Muscle.

In the best studied cases (Aplysia feeding, crustacean stomatogastric system), peptidergic modulation is mediated by large numbers of peptides. Furthermore, in Aplysia, excitatory motor neurons release the peptides, obligatorily coupling target activation and modulator release. Vertebrate nervous systems typically contain about a hundred peptide modulators. These data have created a belief that modulation is, in general, complex. The stick insect leg is a well-studied locomotory model system, and the complete stick insect neuropeptide inventory was recently described. We used multiple techniques to comprehensively examine stick insect leg peptidergic modulation. Single-cell mass spectrometry (MS) and immunohistochemistry showed that myoinhibitory peptide (MIP) is the only neuronal (as opposed to hemolymph-borne) peptide modulator of all leg muscles. Leg muscle excitatory motor neurons contained no neuropeptides. Only the common inhibitor (CI) and dorsal unpaired median (DUM) neuron groups, each neuron of which innervates a group of functionally-related leg muscles, contained MIP. We described MIP transport to, and receptor presence in, one leg muscle, the extensor tibiae (ExtTi). MIP application reduced ExtTi slow fiber force and shortening by about half, increasing the muscle's ability to contract and relax rapidly. These data show neuromodulation does not need to be complex. Excitation and modulation do not need to be obligatorily coupled (Aplysia feeding). Modulation does not need to involve large numbers of peptides, with the attendant possibility of combinatorial explosion (stomatogastric system). Modulation can be simple, mediated by dedicated regulatory neurons, each innervating a single group of functionally-related targets, and all using the same neuropeptide.SIGNIFICANCE STATEMENT Vertebrate and invertebrate nervous systems contain large numbers (around a hundred in human brain) of peptide neurotransmitters. In prior work, neuropeptide modulation has been complex, either obligatorily coupling postsynaptic excitation and modulation, or large numbers of peptides modulating individual neural networks. The complete stick insect neuropeptide inventory was recently described. We comprehensively describe here peptidergic modulation in the stick insect leg. Surprisingly, out of the large number of potential peptide transmitters, only myoinhibitory peptide (MIP) was present in neurons innervating leg muscles. Furthermore, the peptide was present only in dedicated regulatory neurons, not in leg excitatory motor neurons. Peptidergic modulation can thus be simple, neither obligatorily coupling target activation and modulation nor involving so many peptides that combinatorial explosion can occur.

Juvenile ecology drives adult morphology in two insect orders.

Most animals undergo ecological niche shifts between distinct life phases, but such shifts can result in adaptive conflicts of phenotypic traits. Metamorphosis can reduce these conflicts by breaking up trait correlations, allowing each life phase to independently adapt to its ecological niche. This process is called adaptive decoupling. It is, however, yet unknown to what extent adaptive decoupling is realized on a macroevolutionary scale in hemimetabolous insects and if the degree of adaptive decoupling is correlated with the strength of ontogenetic niche shifts. It is also unclear whether the degree of adaptive decoupling is correlated with phenotypic disparity. Here, we quantify nymphal and adult trait correlations in 219 species across the whole phylogeny of earwigs and stoneflies to test whether juvenile and adult traits are decoupled from each other. We demonstrate that adult head morphology is largely driven by nymphal ecology, and that adult head shape disparity has increased with stronger ontogenetic niche shifts in some stonefly lineages. Our findings implicate that the hemimetabolan metamorphosis in earwigs and stoneflies does not allow for high degrees of adaptive decoupling, and that high phenotypic disparity can even be realized when the evolution of distinct life phases is coupled.

Four myriapod relatives - but who are sisters? No end to debates on relationships among the four major myriapod subgroups.

BACKGROUND: Phylogenetic relationships among the myriapod subgroups Chilopoda, Diplopoda, Symphyla and Pauropoda are still not robustly resolved. The first phylogenomic study covering all subgroups resolved phylogenetic relationships congruently to morphological evidence but is in conflict with most previously published phylogenetic trees based on diverse molecular data. Outgroup choice and long-branch attraction effects were stated as possible explanations for these incongruencies. In this study, we addressed these issues by extending the myriapod and outgroup taxon sampling using transcriptome data. RESULTS: We generated new transcriptome data of 42 panarthropod species, including all four myriapod subgroups and additional outgroup taxa. Our taxon sampling was complemented by published transcriptome and genome data resulting in a supermatrix covering 59 species. We compiled two data sets, the first with a full coverage of genes per species (292 single-copy protein-coding genes), the second with a less stringent coverage (988 genes). We inferred phylogenetic relationships among myriapods using different data types, tree inference, and quartet computation approaches. Our results unambiguously support monophyletic Mandibulata and Myriapoda. Our analyses clearly showed that there is strong signal for a single unrooted topology, but a sensitivity of the position of the internal root on the choice of outgroups. However, we observe strong evidence for a clade Pauropoda+Symphyla, as well as for a clade Chilopoda+Diplopoda. CONCLUSIONS: Our best quartet topology is incongruent with current morphological phylogenies which were supported in another phylogenomic study. AU tests and quartet mapping reject the quartet topology congruent to trees inferred with morphological characters. Moreover, quartet mapping shows that confounding signal present in the data set is sufficient to explain the weak signal for the quartet topology derived from morphological characters. Although outgroup choice affects results, our study could narrow possible trees to derivatives of a single quartet topology. For highly disputed relationships, we propose to apply a series of tests (AU and quartet mapping), since results of such tests allow to narrow down possible relationships and to rule out confounding signal.

The loss of flight in ant workers enabled an evolutionary redesign of the thorax for ground labour.

BACKGROUND: Explanations for the ecological dominance of ants generally focus on the benefits of division of labour and cooperation during foraging. However, the principal innovation of ants relative to their wasp ancestors was the evolution of a new phenotype: a wingless worker caste optimized for ground labour. Ant workers are famous for their ability to lift and carry heavy loads, but we know surprisingly little about the morphological basis of their strength. Here we examine the consequences of the universal loss of flight in ant workers on skeletomuscular adaptations in the thorax for enhanced foraging on six legs. RESULTS: Using X-ray microcomputed tomography and 3D segmentation, we compared winged queens and wingless workers in Euponera sikorae (subfamily Ponerinae) and Cataglyphis savignyi (subfamily Formicinae). Workers are characterized by five major changes to their thorax: i) fusion of the articulated flight thorax (queens) into a rigid box optimized to support the muscles that operate the head, legs and abdomen, ii) redesign of internal cuticular structures for better bracing and muscle attachment, iii) substantial enlargement of the neck muscles for suspending and moving the head, iv) lengthening of the external trochanter muscles, predominant for the leg actions that lift the body off the ground, v) modified angle of the petiole muscles that are key for flexion of the abdomen. We measured volumes and pennation angles for a few key muscles to assess their increased efficacy. Our comparisons of additional workers across five genera in subfamilies Dorylinae and Myrmicinae show these modifications in the wingless thorax to be consistent. In contrast, a mutillid wasp showed a different pattern of muscle adaptations resulting from the lack of wing muscles. CONCLUSIONS: Rather than simply a subtraction of costly flight muscles, we propose the ant worker thorax evolved into a power core underlying stronger mandibles, legs, and sting. This contrasts with solitary flightless insects where the lack of central place foraging generated distinct selective pressures for rearranging the thorax. Stronger emphasis is needed on morphological innovations of social insects to further our understanding of the evolution of social behaviours.

Computational biomechanics changes our view on insect head evolution.

Despite large-scale molecular attempts, the relationships of the basal winged insect lineages dragonflies, mayflies and neopterans, are still unresolved. Other data sources, such as morphology, suffer from unclear functional dependencies of the structures considered, which might mislead phylogenetic inference. Here, we assess this problem by combining for the first time biomechanics with phylogenetics using two advanced engineering techniques, multibody dynamics analysis and finite-element analysis, to objectively identify functional linkages in insect head structures which have been used traditionally to argue basal winged insect relationships. With a biomechanical model of unprecedented detail, we are able to investigate the mechanics of morphological characters under biologically realistic load, i.e. biting. We show that a range of head characters, mainly ridges, endoskeletal elements and joints, are indeed mechanically linked to each other. An analysis of character state correlation in a morphological data matrix focused on head characters shows highly significant correlation of these mechanically linked structures. Phylogenetic tree reconstruction under different data exclusion schemes based on the correlation analysis unambiguously supports a sistergroup relationship of dragonflies and mayflies. The combination of biomechanics and phylogenetics as it is proposed here could be a promising approach to assess functional dependencies in many organisms to increase our understanding of phenotypic evolution.

Evolutionary ecology of beta-lactam gene clusters in animals.

Beta-lactam biosynthesis was thought to occur only in fungi and bacteria, but we recently reported the presence of isopenicillin N synthase in a soil-dwelling animal, Folsomia candida. However, it has remained unclear whether this gene is part of a larger beta-lactam biosynthesis pathway and how widespread the occurrence of penicillin biosynthesis is among animals. Here, we analysed the distribution of beta-lactam biosynthesis genes throughout the animal kingdom and identified a beta-lactam gene cluster in the genome of F. candida (Collembola), consisting of isopenicillin N synthase (IPNS), δ-(L-α-aminoadipoyl)-L-cysteinyl-D-valine synthetase (ACVS), and two cephamycin C genes (cmcI and cmcJ) on a genomic scaffold of 0.76 Mb. All genes are transcriptionally active and are inducible by stress (heat shock). A beta-lactam compound was detected in vivo using an ELISA beta-lactam assay. The gene cluster also contains an ABC transporter which is coregulated with IPNS and ACVS after heat shock. Furthermore, we show that different combinations of beta-lactam biosynthesis genes are present in over 60% of springtail families, but they are absent from genome- and transcript libraries of other animals including close relatives of springtails (Protura, Diplura and insects). The presence of beta-lactam genes is strongly correlated with an euedaphic (soil-living) lifestyle. Beta-lactam genes IPNS and ACVS each form a phylogenetic clade in between bacteria and fungi, while cmcI and cmcJ genes cluster within bacteria. This suggests a single horizontal gene transfer event most probably from a bacterial host, followed by differential loss in more recently evolving species.

Musculoskeletal modelling of the dragonfly mandible system as an aid to understanding the role of single muscles in an evolutionary context.

Insects show a great variety of mouthpart and muscle configurations; however, knowledge of their mouthpart kinematics and muscle activation patterns is fragmentary. Understanding the role of muscle groups during movement and comparing them between insect groups could yield insights into evolutionary patterns and functional constraints. Here, we developed a mathematical inverse dynamic model including distinct muscles for an insect head-mandible-muscle complex based on micro-computed tomography (µCT) data and bite force measurements. With the advent of µCT, it is now possible to obtain precise spatial information about muscle attachment areas and head capsule construction in insects. Our model shows a distinct activation pattern for certain fibre groups potentially related to a geometry-dependent optimization. Muscle activation patterns suggest that intramandibular muscles play a minor role in bite force generation, which is a potential reason for their loss in several lineages of higher insects. Our model is in agreement with previous studies investigating fast and slow muscle fibres and is able to resolve the spatio-temporal activation patterns of these different muscle types in insects. The model used here has a high potential for large-scale comparative analyses on the role of different muscle setups and head capsule designs in the megadiverse insects in order to aid our understanding of insect head capsule and mouthpart evolution under mechanical constraints.

The first venomous crustacean revealed by transcriptomics and functional morphology: remipede venom glands express a unique toxin cocktail dominated by enzymes and a neurotoxin.

Animal venoms have evolved many times. Venomous species are especially common in three of the four main groups of arthropods (Chelicerata, Myriapoda, and Hexapoda), which together represent tens of thousands of species of venomous spiders, scorpions, centipedes, and hymenopterans. Surprisingly, despite their great diversity of body plans, there is no unambiguous evidence that any crustacean is venomous. We provide the first conclusive evidence that the aquatic, blind, and cave-dwelling remipede crustaceans are venomous and that venoms evolved in all four major arthropod groups. We produced a three-dimensional reconstruction of the venom delivery apparatus of the remipede Speleonectes tulumensis, showing that remipedes can inject venom in a controlled manner. A transcriptomic profile of its venom glands shows that they express a unique cocktail of transcripts coding for known venom toxins, including a diversity of enzymes and a probable paralytic neurotoxin very similar to one described from spider venom. We screened a transcriptomic library obtained from whole animals and identified a nontoxin paralog of the remipede neurotoxin that is not expressed in the venom glands. This allowed us to reconstruct its probable evolutionary origin and underlines the importance of incorporating data derived from nonvenom gland tissue to elucidate the evolution of candidate venom proteins. This first glimpse into the venom of a crustacean and primitively aquatic arthropod reveals conspicuous differences from the venoms of other predatory arthropods such as centipedes, scorpions, and spiders and contributes valuable information for ultimately disentangling the many factors shaping the biology and evolution of venoms and venomous species.

Structural mouthpart interaction evolved already in the earliest lineages of insects.

In butterflies, bees, flies and true bugs specific mouthparts are in close contact or even fused to enable piercing, sucking or sponging of particular food sources. The common phenomenon behind these mouthpart types is a complex composed of several consecutive mouthparts which structurally interact during food uptake. The single mouthparts are thus only functional in conjunction with other adjacent mouthparts, which is fundamentally different to biting-chewing. It is, however, unclear when structural mouthpart interaction (SMI) evolved since this principle obviously occurred multiple times independently in several extant and extinct winged insect groups. Here, we report a new type of SMI in two of the earliest wingless hexapod lineages--Diplura and Collembola. We found that the mandible and maxilla interact with each other via an articulatory stud at the dorsal side of the maxillary stipes, and they are furthermore supported by structures of the hypopharynx and head capsule. These interactions are crucial stabilizing elements during food uptake. The presence of SMI in these ancestrally wingless insects, and its absence in those crustacean groups probably ancestral to insects, indicates that SMI is a groundplan apomorphy of insects. Our results thus contradict the currently established view of insect mouthpart evolution that biting-chewing mouthparts without any form of SMI are the ancestral configuration. Furthermore, SMIs occur in the earliest insects in a high anatomical variety. SMIs in stemgroup representatives of insects may have triggered efficient exploitation and fast adaptation to new terrestrial food sources much earlier than previously supposed.

The identification of concerted convergence in insect heads corroborates palaeoptera.

The relationships of the 3 major clades of winged insects-Ephemeroptera, Odonata, and Neoptera-are still unclear. Many morphologists favor a clade Metapterygota (Odonata +Neoptera), but Chiastomyaria (Ephemeroptera + Neoptera) or Palaeoptera (Ephemeroptera +Odonata) has also been supported in some older and more recent studies. A possible explanation for the difficulties in resolving these relationships is concerted convergence-the convergent evolution of entire character complexes under the same or similar selective pressures. In this study, we analyze possible instances of this phenomenon in the context of head structures of Ephemeroptera, Odonata, and Neoptera. We apply a recently introduced formal approach to detect the occurrence of concerted convergence. We found that characters of the tentorium and mandibles in particular, but also some other head structures, have apparently not evolved independently, and thus can cause artifacts in tree reconstruction. Our subsequent analyses, which exclude character sets that may be affected by concerted convergence, corroborate the Palaeoptera concept. We show that the analysis of homoplasy and its influence on tree inference can be formally improved with important consequences for the identification of incompatibilities between data sets. Our results suggest that modified weighting (or exclusion of characters) in cases of formally identified correlated cliques of characters may improve morphology-based tree reconstruction.

Head morphology of Tricholepidion gertschi indicates monophyletic Zygentoma.

The relic silverfish Tricholepidion gertschi is the sole extant representative of the family Lepidotrichidae. Its phylogenetic position is of special interest, since it may provide crucial insights into the early phenotypic evolution of the dicondylian insects. However, the phylogenetic position of T. gertschi is unclear. Originally, it was classified among silverfish (Zygentoma), but various alternative relationships within Zygentoma as well as a sistergroup relationship to all remaining Zygentoma + Pterygota are discussed, the latter implying a paraphyly of Zygentoma with respect to Pterygota. Since characters of the head anatomy play a major role in this discussion, we here present the so far most detailed description of the head of T. gertschi based on anatomical studies by synchrotron micro-computer tomography and scanning electron microscopy. A strong focus is put on the documentation of mouthparts and the anatomy of the endoskeleton as well as the muscle equipment. In contrast to former studies we could confirm the presence of a Musculus hypopharyngomandibularis (0md4). The ligamentous connection between the mandibles composed of Musculus tentoriomandibularis inferior (0md6) is also in contact with the anterior tentorium. Phylogenetic analysis of cephalic data results in monophyletic Zygentoma including T. gertschi. Zygentoma are supported by the presence of a set of labial muscles originating at the postocciput, presence of an additional intralabral muscle, and four labial palpomeres. Character systems like the genitalic system, the mating behaviour, the segmentation of the tarsi, the overall body form, and the presence of ocelli which were proposed in other studies as potentially useful for phylogenetic reconstruction are evaluated.

Linking shape conspicuous asymmetry with shape covariation patterns and performance in the insect head and mandibles.

Bilateral symmetry is widespread across animals, yet, among bilaterians, many cases of conspicuous asymmetries evolved. This means that bilaterally homologous structures on the left and right sides display divergent phenotypes. The evolution of such divergent phenotypes between otherwise similarly shaped structures can be thought to be favored by modularity, but this has rarely been studied in the context of left-right differences. Here, we provide an empirical example, using geometric morphometrics to assess patterns of asymmetry and covariation between landmark partitions in a grasshopper with conspicuously asymmetric mandibles. Our morphometric data confirm the presence of strictly directional conspicuous asymmetry in the mandibles and surrounding structures. Covariance patterns and tests hint at a strong integration between mandibles despite their divergent morphologies, and variational modularity with the head capsule. While mandibles have been selected to achieve a key-and-lock morphology by having interlocking shapes, the developmental modularity required to achieve this seems to be overwritten by developmental and/or functional integration, allowing the precise matching required for feeding. The consequent conflicting covariation patterns are reminiscent of the palimpsest model. Finally, the degree of directional asymmetry appears to be under selection, although we find no relationship between bite force and mandible shape or asymmetry.

A bite force database of 654 insect species.

Bite force is a decisive performance trait in animals because it plays a role for numerous life history components such as food consumption, inter- and intraspecific interactions, and reproductive success. Bite force has been studied across a wide range of vertebrate species, but only for 32 species of insects, the most speciose animal lineage. Here we present the insect bite force database with bite force measurements for 654 insect species covering 476 genera, 111 families, and 13 orders with body lengths ranging from 3.76 to 180.12 mm. In total we recorded 1906 bite force series from 1290 specimens, and, in addition, present basal head, body, and wing metrics. As such, the database will facilitate a wide range of studies on the characteristics, predictors, and macroevolution of bite force in the largest clade of the animal kingdom and may serve as a basis to further our understanding of macroevolutionary processes in relation to bite force across all biting metazoans.

Revival of Palaeoptera-head characters support a monophyletic origin of Odonata and Ephemeroptera (Insecta).

The earliest branching event in winged insects, one of the core problems regarding early insect evolution, was addressed using characters of the head. The head is arguably one of the most complex body regions in insects and the phylogenetic information content of its features has been demonstrated. In contrast, the wings and other body parts related to the flight apparatus and sperm transmission are not useful in the context of this problem, as the outgroups (silverfish and bristletails) are wingless and transmit spermatophores externally. Therefore, they show profound differences in the organization of the postcephalic body, and assessment of homology and subsequent phylogenetic analysis of features of these body regions is extremely difficult. The core of this study is the investigation of head structures of representatives of the major clades of dragonflies. A detailed description of the head of Lestes virens is presented and was used as a starting point for the compilation of a character set and a character state matrix for the entire Dicondylia (winged insects + silverfish), with a main focus on the placement of dragonflies and consequently the basal branching event within winged insects. Our results indicate a sister-group relationship between a clade Palaeoptera (dragonflies + mayflies) and the megadiverse monophyletic lineage Neoptera. We show that despite considerable structural similarity between the odonate and neopteran mandible, the muscle equipment in dragonflies is more plesiomorphic with respect to Dicondylia than previously known. Odonata and Ephemeroptera also share presumably derived features of the antenna, maxilla, and labial musculature. Parsimony analyses of the head data unambiguously support a clade Palaeoptera. © The Willi Hennig Society 2012.

Suspension feeders: diversity, principles of particle separation and biomimetic potential.

Suspension feeders (SFs) evolved a high diversity of mechanisms, sometimes with remarkably convergent morphologies, to retain plankton, detritus and man-made particles with particle sizes ranging from less than 1 µm to several centimetres. Based on an extensive literature review, also including the physical and technical principles of solid-liquid separation, we developed a set of 18 ecological and technical parameters to review 35 taxa of suspension-feeding Metazoa covering the diversity of morphological and functional principles. This includes passive SFs, such as gorgonians or crinoids that use the ambient flow to encounter particles, and sponges, bivalves or baleen whales, which actively create a feeding current. Separation media can be flat or funnel-shaped, built externally such as the filter houses in larvaceans, or internally, like the pleated gills in bivalves. Most SFs feed in the intermediate flow region of Reynolds number 1-50 and have cleaning mechanisms that allow for continuous feeding. Comparison of structure-function patterns in SFs to current filtration technologies highlights potential solutions to common technical design challenges, such as mucus nets which increase particle adhesion in ascidians, vanes which reduce pressure losses in whale sharks and changing mesh sizes in the flamingo beak which allow quick adaptation to particle sizes.

A previously unknown feeding mode in millipedes and the convergence of fluid feeding across arthropods.

We report fluid feeding with a sucking pump in the arthropod class Diplopoda, using a combination of synchrotron tomography, histology, electron microscopy, and three-dimensional reconstructions. Within the head of nine species of the enigmatic Colobognatha, we found a pumping chamber, which acts as positive displacement pump and is notably similar to that of insects, showing even fine structural convergences. The sucking pump of these millipedes works together with protractible mouthparts and externally secreted saliva for the acquisition of liquid food. Fluid feeding is one of the great evolutionary innovations of terrestrial arthropods, and our study suggests that it evolved with similar biomechanical solutions convergent across all major arthropod taxa. While fluid-feeding insects are megadiverse today, it remains unclear why other lineages, such as Colobognatha, are comparably species poor.

Ultra high-resolution biomechanics suggest that substructures within insect mechanosensors decisively affect their sensitivity.

Insect load sensors, called campaniform sensilla (CS), measure strain changes within the cuticle of appendages. This mechanotransduction provides the neuromuscular system with feedback for posture and locomotion. Owing to their diverse morphology and arrangement, CS can encode different strain directions. We used nano-computed tomography and finite-element analysis to investigate how different CS morphologies within one location-the femoral CS field of the leg in the fruit fly Drosophila-interact under load. By investigating the influence of CS substructures' material properties during simulated limb displacement with naturalistic forces, we could show that CS substructures (i.e. socket and collar) influence strain distribution throughout the whole CS field. Altered socket and collar elastic moduli resulted in 5% relative differences in displacement, and the artificial removal of all sockets caused differences greater than 20% in cap displacement. Apparently, CS sockets support the distribution of distal strain to more proximal CS, while collars alter CS displacement more locally. Harder sockets can increase or decrease CS displacement depending on sensor location. Furthermore, high-resolution imaging revealed that sockets are interconnected in subcuticular rows. In summary, the sensitivity of individual CS is dependent on the configuration of other CS and their substructures.

Ovipositor and mouthparts in a fossil insect support a novel ecological role for early orthopterans in 300 million years old forests.

A high portion of the earliest known insect fauna is composed of the so-called 'lobeattid insects', whose systematic affinities and role as foliage feeders remain debated. We investigated hundreds of samples of a new lobeattid species from the Xiaheyan locality using a combination of photographic techniques, including reflectance transforming imaging, geometric morphometrics, and biomechanics to document its morphology, and infer its phylogenetic position and ecological role. Ctenoptilus frequens sp. nov. possessed a sword-shaped ovipositor with valves interlocked by two ball-and-socket mechanisms, lacked jumping hind-legs, and certain wing venation features. This combination of characters unambiguously supports lobeattids as stem relatives of all living Orthoptera (crickets, grasshoppers, katydids). Given the herein presented and other remains, it follows that this group experienced an early diversification and, additionally, occurred in high individual numbers. The ovipositor shape indicates that ground was the preferred substrate for eggs. Visible mouthparts made it possible to assess the efficiency of the mandibular food uptake system in comparison to a wide array of extant species. The new species was likely omnivorous which explains the paucity of external damage on contemporaneous plant foliage.

Location and arrangement of campaniform sensilla in Drosophila melanogaster.

Sensory systems provide input to motor networks on the state of the body and environment. One such sensory system in insects is the campaniform sensilla (CS), which detect deformations of the exoskeleton arising from resisted movements or external perturbations. When physical strain is applied to the cuticle, CS external structures are compressed, leading to transduction in an internal sensory neuron. In Drosophila melanogaster, the distribution of CS on the exoskeleton has not been comprehensively described. To investigate CS number, location, spatial arrangement, and potential differences between individuals, we compared the front, middle, and hind legs of multiple flies using scanning electron microscopy. Additionally, we imaged the entire body surface to confirm known CS locations. On the legs, the number and relative arrangement of CS varied between individuals, and single CS of corresponding segments showed characteristic differences between legs. This knowledge is fundamental for studying the relevance of cuticular strain information within the complex neuromuscular networks controlling posture and movement. This comprehensive account of all D. melanogaster CS helps set the stage for experimental investigations into their responsivity, sensitivity, and roles in sensory acquisition and motor control in a light-weight model organism.