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Although organ systems evolve in response to many intrinsic and extrinsic factors, frequently one factor has a dominating influence. For example, mouthpart shape and mechanics are thought to correlate strongly with aspects of the diet. Within insects, this paradigm of a shape-diet connection is advocated for decades but the relationship has so far never been quantified and is mostly based on qualitative observations. Orthoptera (grasshoppers, crickets, and allies) are a prominent case, for which mandible shape and dietary preference are thought to correlate strongly and even lead to predictions of feeding preferences. Here, we analysed mandible shape, biting efficiency, and their potential correlation with dietary categories in a phylogenetic framework for a broad sampling of several hundred extant Orthoptera covering nearly all families. The mandibular mechanical advantage was used as a descriptor of gnathal edge shape and bite force transmission efficiency. We aimed to understand how mandible shape is linked to biting efficiency and diet, and how these traits are influenced by phylogeny and allometry. The investigation reveals that feeding ecology is not the unequivocal predictor of mandible shape that it was assumed to be. There is a strong phylogenetic signal suggesting that phylogenetic history does have a much more prevalent influence on gnathal edge shape and distal mechanical advantage, than, e.g., feeding guilds or the efficiency of the force transmission to the food. Being ancestrally phytophagous, Orthoptera evolved in an environment with abundant food sources so that selective pressures leading to more specialized mouthpart shapes and force transmission efficiencies were low.

In recent years, the study of insect morphology has benefited greatly from the emergence of new digital imaging and analysis technologies such as X-ray micro-computed tomography (μ-CT), digital 3D reconstruction, and animation. Through interactive gaming and virtual reality, the external morphology of insects can be studied by a broad audience of both entomologists and non-specialists. EntomonVR is a serious game designed to investigate the external morphology of insects with adequate quality for the virtual reality platform. We discuss the advantages of virtual reality, introduce the EntomonVR new educational game, and conclude about future perspectives, validations, and cost-effectiveness. For game assessment, we have tested this game on 25 participants with an entomological background and improved the game based on their feedback. This study demonstrates the efficacy of virtual reality technology for an experimental learning environment in teaching the morphology of insects and the crucial needs for advancing an efficient and interactive educational program.

Fossils provide unique opportunity to understand the tempo and mode of evolution and are essential for modeling the history of lineage diversification. Here, we interrogate the Mesozoic fossil record of the Aculeata, with emphasis on the ants (Formicidae), and conduct an extended series of ancestral state estimation exercises on distributions of tip-dated combined-evidence phylogenies. We developed and illustrated from ground-up a series of 576 morphological characters which we scored for 144 extant and 431 fossil taxa, including all families of Aculeata, Trigonaloidea, Evanioidea, and †Ephialtitoidea. We used average posterior probability support to guide composition of a target matrix of 303 taxa, for which we integrated strongly filtered ultraconserved element (UCE) data for 115 living species. We also implemented reversible jump MCMC (rjMCMC) and hidden state methods to model complex behavioral characters to test hypotheses about the pathway to obligate eusociality. In addition to revising the higher classification of all sampled groups to family or subfamily level using estimated character polarities to diagnose nodes across the phylogeny, we find that the mid-Cretaceous genera †Camelomeciaand †Camelospheciaform a clade which is robustly supported as sister to all living and fossil Formicidae. For this reason, we name this extinct clade as †@@@idaefam. nov.and provide a definition for the expanded Formicoidea. Based on our results, we recognize three major phases in the early evolution of the ants: (1) origin of Formicoidea as ground-adapted huntresses during the Late Jurassic in the “stinging aggressor” guild (Aculeata) among various lineages of “sneaking parasitoids” (non-aculeate Vespina); (2) the first formicoid radiation during the Early Cretaceous, by the end of which all major extant linages originated; and (3) turnover of the Formicoidea at the end-Cretaceous leading to the second formicoid radiation. We conclude with a concentrated series of considerations for future directions of study with this dataset and beyond.

The extraordinary success of social insects is partially based on ‘division of labour’, i. e. individuals exclusively or preferentially perform specific tasks. Task-preference may correlate with morphological adaptations so implying task-specialisation, but the extent of such specialisation can be difficult to determine. Here, we demonstrate how the physical foundation of some tasks can be leveraged to quantitatively link morphology and performance. We study the allometry of bite force capacity inAtta vollenweiderileaf-cutter ants, polymorphic insects in which the mechanical processing of plant material is a key aspect of the behavioural portfolio. Through a morphometric analysis of tomographic scans, we show that the bite force capacity of the heaviest colony workers is twice as large as predicted by isometry. This disproportionate ‘boost’ is predominantly achieved through increased investment in muscle volume; geometrical parameters such as mechanical advantage, fibre length or pennation angle are likely constrained by the need to maintain a constant mandibular opening range. We analyse this preference for an increase in size-specific muscle volume and the adaptations in internal and external head anatomy required to accommodate it with simple geometric and physical models, so providing a quantitative understanding of the functional anatomy of the musculoskeletal bite apparatus in insects.

2.AbstractSuction organs provide powerful yet dynamic attachments for many aquatic animals, including octopus, squid, remora, and clingfish. While the functional morphology of suction organs from various cephalopods and fishes has been investigated in detail, there are only few studies on such attachment devices in insects. Here we characterise the morphology, ultrastructure, andin vivomovements of the suction attachment organs of net-winged midge larvae (genusLiponeura) – aquatic insects that live on rocks in rapid alpine waterways where flow rates can reach 3 m s-1– using scanning electron microscopy, laser confocal scanning microscopy, and X-ray computed micro-tomography (micro-CT). We identified structural adaptations important for the function of the suction attachment organs fromL. cinerascensandL. cordata. First, a dense array of spine-like microtrichia covering each suction disc comes into contact with the substrate upon attachment. Similar hairy structures have been found on the contact zones of suction organs from octopus, clingfish, and remora fish. These structures are thought to contribute to the seal and to provide increased shear force resistance in high-drag environments. Second, specialised rim microtrichia at the suction disc periphery form a continuous ring in close contact with a surface and may serve as a seal on a variety of surfaces. Third, a V-shaped cut on the suction disc (the V-notch) is actively peeled open via two cuticular apodemes inserting into its flanks. The apodemes are attached to dedicated V-notch opening muscles, thereby providing a unique detachment mechanism. The complex cuticular design of the suction organs, along with specialised muscles that attach to them, allows blepharicerid larvae to generate powerful attachments which can withstand strong hydrodynamic forces and quickly detach for locomotion. Our findings could be applied to bio-inspired attachment devices that perform well on a wide range of surfaces.