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In addition to generating lift by leading-edge vortices (as used by most insects), mosquitoes also employ trailing-edge vortices and a lift mechanism from wing rotation, which enables them to stay airborne despite having a seemingly unlikely airframe. On the wings of a mosquito As anyone who has shared a bedroom with a mosquito will attest, mosquitos beat their wings fast enough for the irritating whine at about 800 Hz to be audible. Strangely, mosquito wings are long and thin, rather than the short and stubby wings expected to support rapid wing beats. The wing beat is also of rather low amplitude; the entire angular sweep of the wing is around 40 degrees, less than half that of the honey bee, whose 91 degree range is regarded as shallow. So how do mosquitoes fly at all? Bomphrey and colleagues show that in addition to generating lift by leading-edge vortices (as used by most insects) mosquitos employ trailing-edge vortices and a lift mechanism caused by the rotation of the wing. This adds to the expanding repertoire of mechanisms that insects use to stay airborne despite a seemingly unlikely airframe. Mosquitoes exhibit unusual wing kinematics; their long, slender wings flap at remarkably high frequencies for their size (>800 Hz)and with lower stroke amplitudes than any other insect group 1 . This shifts weight support away from the translation-dominated, aerodynamic mechanisms used by most insects 2 , as well as by helicopters and aeroplanes, towards poorly understood rotational mechanisms that occur when pitching at the end of each half-stroke. Here we report free-flight mosquito wing kinematics, solve the full Navier–Stokes equations using computational fluid dynamics with overset grids, and validate our results with in vivo flow measurements. We show that, although mosquitoes use familiar separated flow patterns, much of the aerodynamic force that supports their weight is generated in a manner unlike any previously described for a flying animal. There are three key features: leading-edge vortices (a well-known mechanism that appears to be almost ubiquitous in insect flight), trailing-edge vortices caused by a form of wake capture at stroke reversal, and rotational drag. The two new elements are largely independent of the wing velocity, instead relying on rapid changes in the pitch angle (wing rotation) at the end of each half-stroke, and they are therefore relatively immune to the shallow flapping amplitude. Moreover, these mechanisms are particularly well suited to high aspect ratio mosquito wings.

\"A stunning world-records book of animal flight, by the author-and-illustrator team behind the bestselling Book of Bones! Meet ten fascinating flyers through a series of superlatives - and guess who's who while learning about airborne animals. From the fastest (white-throated needletail) to the most acrobatic (flying fox bat), and from the best glider (colugo) to the best backward flyer (hummingbird), each master of flight is cleverly depicted in a blueprint-inspired diagram, accompanied by playful, informative text. The stunning page-turn reveal features a full-colour illustration and an explanation of what makes each animal's way of flying so special. Ages 5-8.\" --Provided by publisher.

Flight speed is positively correlated with body size in animals 1 . However, miniature featherwing beetles can fly at speeds and accelerations of insects three times their size 2 . Here we show that this performance results from a reduced wing mass and a previously unknown type of wing-motion cycle. Our experiment combines three-dimensional reconstructions of morphology and kinematics in one of the smallest insects, the beetle Paratuposa placentis (body length 395 μm). The flapping bristled wings follow a pronounced figure-of-eight loop that consists of subperpendicular up and down strokes followed by claps at stroke reversals above and below the body. The elytra act as inertial brakes that prevent excessive body oscillation. Computational analyses suggest functional decomposition of the wingbeat cycle into two power half strokes, which produce a large upward force, and two down-dragging recovery half strokes. In contrast to heavier membranous wings, the motion of bristled wings of the same size requires little inertial power. Muscle mechanical power requirements thus remain positive throughout the wingbeat cycle, making elastic energy storage obsolete. These adaptations help to explain how extremely small insects have preserved good aerial performance during miniaturization, one of the factors of their evolutionary success. Three-dimensional reconstructions of morphology and flight mechanics of the beetle Paratuposa placentis reveal adaptations that enable extremely small insects to fly at speeds similar to those of much larger insects.

A celebration of the miraculous phenomenon of flight through 14 species and across millions of years - from pterosaurs to dragonflies, butterflies to albatross.

The wings of Lepidoptera contain a matrix of living cells whose function requires appropriate temperatures. However, given their small thermal capacity, wings can overheat rapidly in the sun. Here we analyze butterfly wings across a wide range of simulated environmental conditions, and find that regions containing living cells are maintained at cooler temperatures. Diverse scale nanostructures and non-uniform cuticle thicknesses create a heterogeneous distribution of radiative cooling that selectively reduces the temperature of structures such as wing veins and androconial organs. These tissues are supplied by circulatory, neural and tracheal systems throughout the adult lifetime, indicating that the insect wing is a dynamic, living structure. Behavioral assays show that butterflies use wings to sense visible and infrared radiation, responding with specialized behaviors to prevent overheating of their wings. Our work highlights the physiological importance of wing temperature and how it is exquisitely regulated by structural and behavioral adaptations. Butterfly wings have low thermal capacity and thus are vulnerable to damage by overheating. Here, Tsai et al. take an interdisciplinary approach to reveal the organs, nanostructures and behaviors that enable butterflies to sense and regulate their wing temperature.

Some insects have alternative wing morphs, one that is long-winged and changes habitat to follow resources, and one that is short-winged and flightless but has high fertility; here, the molecular details of this switch are revealed, with opposite effects of two insulin receptors controlling the development of different wing morphs in the planthopper. Insect double identity is insulin-linked Some types of insect can exist in two forms, both as long-winged morphs that can move from habitat to habitat to follow resources, and as short-winged flightless morphs with high fertility, but the molecular details of this switch have remained unclear. One species that leads this double life is the migratory brown planthopper Nilaparvata lugens , a serious pest in rice-growing regions of Asia. Chuan-Xi Zhang and colleagues show that long-wing versus short-wing development in N. lugens is controlled through the opposing effects of two insulin receptors, InR1 and InR2, on the activity of the forkhead transcription factor Foxo. Wing polyphenism is an evolutionarily successful feature found in a wide range of insects 1 . Long-winged morphs can fly, which allows them to escape adverse habitats and track changing resources, whereas short-winged morphs are flightless, but usually possess higher fecundity than the winged morphs 1 , 2 , 3 . Studies on aphids, crickets and planthoppers have revealed that alternative wing morphs develop in response to various environmental cues 1 , 2 , 4 , 5 , 6 , 7 , 8 , and that the response to these cues may be mediated by developmental hormones, although research in this area has yielded equivocal and conflicting results about exactly which hormones are involved 4 , 8 , 9 , 10 . As it stands, the molecular mechanism underlying wing morph determination in insects has remained elusive. Here we show that two insulin receptors in the migratory brown planthopper Nilaparvata lugens , InR1 and InR2, have opposing roles in controlling long wing versus short wing development by regulating the activity of the forkhead transcription factor Foxo. InR1, acting via the phosphatidylinositol-3-OH kinase (PI(3)K)–protein kinase B (Akt) signalling cascade, leads to the long-winged morph if active and the short-winged morph if inactive. InR2, by contrast, functions as a negative regulator of the InR1–PI(3)K–Akt pathway: suppression of InR2 results in development of the long-winged morph. The brain-secreted ligand Ilp3 triggers development of long-winged morphs. Our findings provide the first evidence of a molecular basis for the regulation of wing polyphenism in insects, and they are also the first demonstration—to our knowledge—of binary control over alternative developmental outcomes, and thus deepen our understanding of the development and evolution of phenotypic plasticity.

Wing colour patterning of multiple species in the butterfly genus Heliconius is controlled by differential expression of the gene cortex , a member of a conserved family of cell cycle regulators. The look of Lepidoptera driven by cortex The darkening of the peppered moth Biston betularia , the phenomenon known as industrial melanism, is a textbook example of evolutionary biology in action. However, the genetic background of the black or c arbonaria variants has remained unclear. Building on their earlier work that isolated the gene responsible to within a roughly 400-kilobase region containing 13 genes, Ilik Saccheri and colleagues have identified the melanism-causing event as the insertion of a class II transposable element into the first intron of a gene called cortex . Statistical inference indicates that the polymorphism occurred around 1819, when the Industrial Revolution was well under way. In a separate study, Nicola Nadeau et al . report that colour patterning in butterflies of the genus Heliconius is also mediated by expression of the cortex gene, apparently co-opted to control the rate of scale cell development, on which colour depends. Taken together, these two papers suggest that cortex , conserved widely within Lepidoptera, is a major target for natural selection acting on colour and pattern variation. The wing patterns of butterflies and moths (Lepidoptera) are diverse and striking examples of evolutionary diversification by natural selection 1 , 2 . Lepidopteran wing colour patterns are a key innovation, consisting of arrays of coloured scales. We still lack a general understanding of how these patterns are controlled and whether this control shows any commonality across the 160,000 moth and 17,000 butterfly species. Here, we use fine-scale mapping with population genomics and gene expression analyses to identify a gene, cortex , that regulates pattern switches in multiple species across the mimetic radiation in Heliconius butterflies. cortex belongs to a fast-evolving subfamily of the otherwise highly conserved fizzy family of cell-cycle regulators 3 , suggesting that it probably regulates pigmentation patterning by regulating scale cell development. In parallel with findings in the peppered moth ( Biston betularia ) 4 , our results suggest that this mechanism is common within Lepidoptera and that cortex has become a major target for natural selection acting on colour and pattern variation in this group of insects.

Morphogens, such as Decapentaplegic (Dpp) in the fly imaginal discs, form graded concentration profiles that control patterning and growth of developing organs. In the imaginal discs, proliferative growth is homogeneous in space, posing the conundrum of how morphogen concentration gradients could control position-independent growth. To understand the mechanism of proliferation control by the Dpp gradient, we quantified Dpp concentration and signaling levels during wing disc growth. Both Dpp concentration and signaling gradients scale with tissue size during development. On average, cells divide when Dpp signaling levels have increased by 50%. Our observations are consistent with a growth control mechanism based on temporal changes of cellular morphogen signaling levels. For a scaling gradient, this mechanism generates position-independent growth rates.

The morphogen Decapentaplegic (Dpp) has been implicated in both wing patterning and growth in fruitflies; here, a nanobody-based morphotrap approach has been developed that rules out a role for the Dpp gradient in regulating lateral wing growth. Drosophila Decapentaplegic (Dpp) has served as a paradigm to study morphogen-dependent growth control. However, the role of a Dpp gradient in tissue growth remains highly controversial. Two fundamentally different models have been proposed: the ‘temporal rule’ model suggests that all cells of the wing imaginal disc divide upon a 50% increase in Dpp signalling, whereas the ‘growth equalization model’ suggests that Dpp is only essential for proliferation control of the central cells. Here, to discriminate between these two models, we generated and used morphotrap, a membrane-tethered anti-green fluorescent protein (GFP) nanobody, which enables immobilization of enhanced (e)GFP::Dpp on the cell surface, thereby abolishing Dpp gradient formation. We find that in the absence of Dpp spreading, wing disc patterning is lost; however, lateral cells still divide at normal rates. These data are consistent with the growth equalization model, but do not fit a global temporal rule model in the wing imaginal disc. Morphogen patterning in Drosophila In Drosophila , the morphogen Decapentaplegic (Dpp), which is homologous to bone morphogenetic protein, has been implicated both in wing patterning and growth. Dpp is secreted from a central stripe in developing wing, and forms a gradient that is thought to be essential for its role in patterning. How the Dpp gradient drives proliferation across the whole tissue has been a matter of debate, joined by two groups reporting in this issue of Nature . Stefan Harmansa et al . have developed a morphotrap approach that relies on the expression of a membrane-tethered GFP antibody to immobilize GFP-tagged Dpp in a specific region of the wing. They show that although the absence of spreading disrupts the patterning of the wing, lateral cells still divide normally, ruling out a role for the Dpp gradient in regulating lateral wing growth. Takuya Akiyama and Matthew Gibson have used a CRISPR–Cas9-mediated approach to ablate Dpp expression specifically in the stripe and although the resulting animals exhibit patterning defects, their cell proliferation and growth remained relatively normal. This rules out a role for the Dpp stripe in modulating wing growth.