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"Animal flight."
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Smart wing rotation and trailing-edge vortices enable high frequency mosquito flight
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.
Journal Article
Can it fly?
Using simple text and pictures, this book presents examples of animals that can fly and animals that can't.
Book
Novel flight style and light wings boost flight performance of tiny beetles
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.
Journal Article
Statistical mechanics for natural flocks of birds
Flocking is a typical example of emergent collective behavior, where interactions between individuals produce collective patterns on the large scale. Here we show how a quantitative microscopic theory for directional ordering in a flock can be derived directly from field data. We construct the minimally structured (maximum entropy) model consistent with experimental correlations in large flocks of starlings. The maximum entropy model shows that local, pairwise interactions between birds are sufficient to correctly predict the propagation of order throughout entire flocks of starlings, with no free parameters. We also find that the number of interacting neighbors is independent of flock density, confirming that interactions are ruled by topological rather than metric distance. Finally, by comparing flocks of different sizes, the model correctly accounts for the observed scale invariance of long-range correlations among the fluctuations in flight direction.
Journal Article
Book of flight : 10 record-breaking animals with 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.
Book
Locust density shapes energy metabolism and oxidative stress resulting in divergence of flight traits
Flight ability is essential for the enormous diversity and evolutionary success of insects. The migratory locusts exhibit flight capacity plasticity in gregarious and solitary individuals closely linked with different density experiences. However, the differential mechanisms underlying flight traits of locusts are largely unexplored. Here, we investigated the variation of flight capacity by using behavioral, physiological, and multiomics approaches. Behavioral assays showed that solitary locusts possess high initial flight speeds and short-term flight, whereas gregarious locusts can fly for a longer distance at a relatively lower speed. Metabolome–transcriptome analysis revealed that solitary locusts have more active flight muscle energy metabolism than gregarious locusts, whereas gregarious locusts show less evidence of reactive oxygen species production during flight. The repression of metabolic activity by RNA interference markedly reduced the initial flight speed of solitary locusts. Elevating the oxidative stress by paraquat injection remarkably inhibited the long-distance flight of gregarious locusts. In respective crowding and isolation treatments, energy metabolic profiles and flight traits of solitary and gregarious locusts were reversed, indicating that the differentiation of flight capacity depended on density and can be reshaped rapidly. The density-dependent flight traits of locusts were attributed to the plasticity of energy metabolism and degree of oxidative stress production but not energy storage. The findings provided insights into the mechanism underlying the trade-off between velocity and sustainability in animal locomotion and movement.
Journal Article
Foraging success of biological Levy flights recorded in situ
It is an open question how animals find food in dynamic natural environments where they possess little or no knowledge of where resources are located. Foraging theory predicts that in environments with sparsely distributed target resources, where forager knowledge about resources' locations is incomplete, Lévy flight movements optimize the success of random searches. However, the putative success of Lévy foraging has been demonstrated only in model simulations. Here, we use high-temporal-resolution Global Positioning System (GPS) tracking of wandering (Diomedea exulans) and black-browed albatrosses (Thalassarche melanophrys) with simultaneous recording of prey captures, to show that both species exhibit Lévy and Brownian movement patterns. We find that total prey masses captured by wandering albatrosses during Lévy movements exceed daily energy requirements by nearly fourfold, and approached yields by Brownian movements in other habitats. These results, together with our reanalysis of previously published albatross data, overturn the notion that albatrosses do not exhibit Lévy patterns during foraging, and demonstrate that Lévy flights of predators in dynamic natural environments present a beneficial alternative strategy to simple, spatially intensive behaviors. Our findings add support to the possibility that biological Lévy flight may have naturally evolved as a search strategy in response to sparse resources and scant information.
Journal Article