Wing Beat Research Articles

CONTENT OF DOCOSAHEXAENOIC ACID IN PECTORAL MUSCLES OF BIRDS CORRELATES WITH WING BEAT FREQUENCY

Docosahexaenoic acid (22:6n–3, DHA) is a structural component of cell membranes and due to a peculiar form of its molecule exerts a high lateral pressure in the membranes enhancing activity of membrane-associated enzymes. A high content of DHA probably provides a high frequency of contraction and a continuous working of skeletal muscles. To estimate the probable physiological and biochemical role of DHA in muscle tissue, a relation of its contents in pectoral muscles of birds with wing beat frequency was evaluated. A high statistically significant correlation between the content of DHA in pectoral muscles of birds and species-specific wing beat frequency was found.

Content of Docosahexaenoic Acid in Pectoral Muscles of Birds Correlates with Wing Beat Frequency.

Docosahexaenoic acid (22:6n-3, DHA) is a structural component of cell membranes and due to a peculiar form of its molecule exerts a high lateral pressure in the membranes enhancing activity of membrane-associated enzymes. A high content of DHA probably provides a high frequency of contraction and a continuous working of skeletal muscles. To estimate the probable physiological and biochemical role of DHA in muscle tissue, a relation of its contents in pectoral muscles of birds with wing beat frequency was evaluated. A high statistically significant correlation between the content of DHA in pectoral muscles of birds and species-specific wing beat frequency was found.

Numerical and Experimental Studies on the Micro-Doppler Signatures of Freely Flying Insects at W-Band

Remote sensing techniques in the microwave frequency range have been successfully used in the context of bird, bat and insect measurements. This article breaks new ground in the analysis of freely flying insects by using a continuous-wave (CW) radar system in W-band, i.e., higher mm-wave frequencies, by measuring and analyzing the micro-Doppler signature of their wing beat motion. In addition to numerical and experimental methods, the investigation also includes the development of a new signal processing method using a cepstrogram approach in order to automatically determine the wing beat frequency. In this study, mosquitoes (culex pipiens) and bees (apis mellifera) are considered as model insects throughout the measurement campaign. It was found that 50 independent micro-Doppler measurements of mosquitoes and bees can be clearly distinguished from each other. Moreover, the proposed radar signal model accurately matches the experimental measurements for both species.

Flight muscle structure and flight capacity of females of the long‐distance migratory armyworm,Spodoptera frugiperda: effect of aging and reproduction, and trade‐offs between flight and fecundity

AbstractInsects in flight achieve the highest metabolism rates and wing beat frequency known in the animal kingdom, but how they do this is not fully understood. Here, we demonstrate the structure and arrangement of flight muscles in the thorax ofSpodoptera frugiperdaSmith & Abbot (Lepidoptera: Noctuidae). Dorsoventral direct flight muscles are stronger and more complicated than dorsoventral indirect flight muscles, which may be important for the moth to swiftly control the trajectory. The abundance of giant mitochondria and the extensive tracheolar system in flight muscle are two prominent features that are well adapted to the special requirements of flight. Parameters of flight muscle and flight capacity were lower in young females, and then increased with time and peaked in middle‐aged females. Mating accelerated the deterioration of the structure and function of flight muscles. Virgin females showed lower ovarian development rate but higher flight capacity than mated females. Further analysis found that female flight capacity was significantly negatively correlated to her fecundity, suggesting a trade‐off between flight and reproduction. The resource allocation to flight and egg production may be the result of a balance between the intensity of natural and sexual selection on both traits.

Membrane muscles tension bat wings for faster flight

Watching a bat flit through the night sky, you might think that the delicate membrane stretched between the animal's elbow, long splayed digit bones and down its side to the hind limbs is no more than an inert flexible surface that catches air passively like fabric covering the struts of a kite. Yet, the elegant wing membrane is spanned by thin thread-like muscles. Could the muscles, known as plagiopatagiales proprii, tense and relax the membrane to fine-tune how the structure bows and catches the air as the animals swoop and flutter? Jorn Cheney, Jeremy Rehm, Sharon Swartz and Kenny Breuer from Brown University, USA, decided to find out.But first, the team need to know how Jamaican fruit bats (Artibeus jamaicensis) fly when they had full use of the wing membrane muscles. Cheney and Rehm tempted the animals with guava juice to fly through still air in a wind tunnel and into a 5 m s−1 head wind, filming the animals with six high-speed cameras to reconstruct the wing shape during their distinctive wingbeats to find out how much the membrane bowed as the animals propelled themselves forward. Then the pair painstakingly paralysed all 25 of the fine muscles in each wing by individually injecting botulism toxin into each, inactivating them temporarily. ‘We use tiny, microliter amounts of dilute Botox, much less than would be used in a cosmetic procedure to minimize a single forehead wrinkle’, says Swartz. Once the animals had recovered, Cheney and Rehm then encouraged the bats to fly again in the still air and headwind, to find out how loss of muscle control affected the animals. The animals with the paralysed wing membrane muscles struggled to remain aloft in the motionless air. Even though they could still fly at 6.2 m s−1 into the head wind – which was 1 m s−1 slower than they had managed with full use of the wing membrane muscles – the animals struggled when there was no headwind, descending rapidly to the ground as they tried to remain aloft. And, when the team compared the bats’ wing membranes as they flew into the head wind, it was clear that the membranes of the paralysed bats were slacker, bowing 12% more than the wing membranes of the bats that still had the use of their plagiopatagiales proprii, also increasing the amount of air drag on the wing to slow the animals by 16%. However, the bats with the immobilised wing membrane muscles managed to compensate for the increased drag by increasing their wing beat amplitude from ∼60 to ∼75 deg and tipping the wing more to sweep it through a less vertical angle.‘Reduced forward speed, reduced ability for low-speed flight and changes in kinematics [when the plagiopatagiales were inactive] are consistent with the plagiopatagiales playing a crucial role in reducing drag through active control over membrane tension indirectly controlling camber’, says Cheney, explaining that using the muscles to tension the wing membrane helps bats to fly at higher speeds. However, the team points out that the bats with the paralysed muscles could have taken advantage of their slacker wing membranes to select slower preferred speeds; so why didn't they? They suspect that the animals may not be able to provide the additional flight power required to remain aloft at the lower speeds caused by bowed wing membranes. The researchers conclude, ‘Jamaican fruit bats likely always employ their wing membrane muscles during sustained flight to control camber [bowing] and to enhance flight efficiency’. And, happily, the bats soon recovered full use of their plagiopatagiales muscles after their wing slackening experience to regain full bat mobility.

Deformable model of a butterfly in motion on the example of Attacus atlas

Insect wings can undergo significant chordwise (camber) as well as spanwise (twist) deformation during flapping flight but the effect of these deformations is not well understood. The shape and size of butterfly wings leads to particularly large wing deformations, making them an ideal test case for investigation of these effects. High-speed videogrammetry was used to capture the wing kinematics and deformations. The movements of selected markers on the wings of a living insect was observed. Created characteristics showing the displacement in a three-dimensional coordinate system identified the kinematics and deformations of the butterfly's wings. These experimental results were then analyzed computationally using a high-fidelity, three-dimensional, unsteady Navier-Stokes flow solver. Computational fluid dynamics (CFD) simulations were carried out on the basis of the wing geometry of the large moth Attacus atlas. Six geometric and structural models of the Attacus atlas butterfly wing with various degrees of simplification were developed. Using these models, Fluid-Structure-Interaction (FSI) simulation studies were performed in the commercial Ansys software environment (Fluent and Mechanical). Computations of the wing beat cycle were carried out, obtaining pressure distributions, streamlines, vortex regions and cumulative force waveforms.

Soaring and intermittent flap-gliding during migratory flights of Northern Bald Ibis

Migratory journeys represent an energetic challenge for many long-distance migrants. The choice of flight times, migration route, altitude, travelling speed, wingbeat patterns, soaring as well as formation flight can all affect the energy expenditure for the journey. We monitored the flight patterns of two Northern Bald Ibises (Geronticus eremita) equipped with data loggers while crossing the Alps during a human-led migration from southern Germany to Tuscany. We observed that the birds used an intermittent flapping pattern, where phases of active flapping flight were regularly interrupted by short gliding phases. As a result of intermittent flight, the effective wing beat frequency was 13–20% lower than the observed wing beat frequency of 4.0 s−1. When local conditions allowed, the birds gained altitude through circling in thermal updrafts. During those circling bouts, gliding on the outstretched wing was predominant, though active wing flapping was still observed. Overall, the two birds spent 19 and 22% of the time soaring on the outstretched wing, accruing during that time 26 and 28% of the altitude gain required for the crossing of a major mountain range. This shows that, apart from formation flight, northern bald ibis use at least two more strategies—thermal soaring and intermittent flap-gliding—for improving energy economy during migratory flights.

Automating insect monitoring using unsupervised near-infrared sensors

Insect monitoring is critical to improve our understanding and ability to preserve and restore biodiversity, sustainably produce crops, and reduce vectors of human and livestock disease. Conventional monitoring methods of trapping and identification are time consuming and thus expensive. Automation would significantly improve the state of the art. Here, we present a network of distributed wireless sensors that moves the field towards automation by recording backscattered near-infrared modulation signatures from insects. The instrument is a compact sensor based on dual-wavelength infrared light emitting diodes and is capable of unsupervised, autonomous long-term insect monitoring over weather and seasons. The sensor records the backscattered light at kHz pace from each insect transiting the measurement volume. Insect observations are automatically extracted and transmitted with environmental metadata over cellular connection to a cloud-based database. The recorded features include wing beat harmonics, melanisation and flight direction. To validate the sensor’s capabilities, we tested the correlation between daily insect counts from an oil seed rape field measured with six yellow water traps and six sensors during a 4-week period. A comparison of the methods found a Spearman’s rank correlation coefficient of 0.61 and a p-value = 0.0065, with the sensors recording approximately 19 times more insect observations and demonstrating a larger temporal dynamic than conventional yellow water trap monitoring.

Mating Behavior and Gonotrophic Cycle in Anopheles gambiae Complex and their Significance in Vector Competence and Malaria Vector Control

Anopheles gambiae complex mosquitoes comprise different morphologically identical species and the most medically important malaria vectors in Africa. Understanding An. gambiae complex mosquitoes’ mating behaviour is a clue for prevention and control of malaria. The factors affecting the mating behavior of An. gambiae complex are age, body size, food finding, type of food, host availability and environmental temperature. An. gambiae complex passes through different and unique mating strategies. The fundamental mechanisms underlying mating behavior of An. gambiae complex are male aggregation before copulation which is called swarming, finding female and insemination. Male in the swarm detects the wing beat of female with which he mates by auditory system. The wing beat frequencies of opposite sex of the same genetic form simply harmonize indicating possible hybridization while that of different genetic forms do not harmonize. The successive mating behavior of female An. gambiae mosquitoes includes, locating a male among the swarm for cupola, friend selection and storage of sperm. Successful female An. gambiae complex mosquitoes mating is accomplished by host seeking, blood feeding and digestion, egg development and oviposition. The sequential process of host finding and blood feeding followed by blood digestion and simultaneously egg maturation and accomplished by searching of oviposition site and oviposition is referred to as gonotrophic cycle. The time period between two successive blood feedings or two successive ovipositions is said to be gonotrophic period. The length of gonotrophic period depends on temperature, number of previous gonotrophic cycle, host and breeding site availability. In addition to population net reproduction of the colony, gonotrophic cycle is also used to estimate female mosquitoes’ age by determining the parity. Finally, understandings of mating behavior and gonotrophic cycle of An. gambiae complex mosquitoes help in malaria vector control strategies and their vector competence.

Age and activity take their toll on house fly wings

Choosing a name can be stressful, so some creatures have simply ended up with literal monikers. Sloths, dung beetles and anteaters pretty much do what their names suggest; or at least they do in English. And then there's the humble fly. Where would these insects be without their wings? This is a question that Fritz-Olaf Lehmann from the University of Rostock, Germany keeps asking. How does the wear and tear that fly wings endure come about? Do the delicate structures simply become more fragile and disintegrate with age, or are they vulnerable to the knockabout of flight and collisions, accumulating damage over time? To find out where and how house flies accumulate damage to their wings, Henja-Niniane Wehmann, Thomas Engels (both from the University of Rostock) and Lehmann teamed up to identify which factors take the greatest toll on house fly wings and how much damage individuals can sustain before they can no longer remain aloft. Initially, Wehmann placed groups of four house flies (Musca domestica) together in small (130 cm3) plastic tubes for their entire lives, monitoring their activity by listening in as the insects buzzed while flying. In addition, she anaesthetised the tiny inhabitants three times a week to trace the outline of their wings and check their deterioration under a microscope. As well as cramming flies together, Wehmann also kept 20 of the insects in a larger mesh enclosure – providing 2000 times more space – regularly photographing them to find out how much of a toll the alternative lifestyle took on their wings.Recording almost 7.7 million flights, ranging from as little as 0.03 s (five wing beats) to 0.92 s for females, but only up to 0.79 s for the males, Wehmann and Engels realised that the insects’ wings first began incurring damage at the tips and rear edges of the fragile transparent membrane, becoming more ragged. However, after about 6 h of flight, the wings began showing signs of really catastrophic damage, fracturing along the front edge and losing larger portions. One fly lost almost 90% of a wing over one calamitous 3 day period.Yet, while there were some clear losers, there were also winners. Some of the closely caged insects lost only 15% of their wing area over their lifetime, while others were left with almost non-existent stubs by the time they died. Also, the flies that were living in the most cramped conditions suffered damage 20 times faster than the insects that had a spacious cage to explore, confirming that impacts contribute significantly to incurred wing damage.In contrast, some of the grounded flies appeared to have lost only 10% of their wing area, while others still managed to remain aloft, having lost as much as 34% of their initial wing area. And when Wehmann plotted the insects’ ages against their ability to fly, it was clear that the most elderly flies were the most likely to have lost the power of flight; age in addition to wear and tear, is a clear risk for wings.So, use and getting old both take a toll on the fragile structures that carry flies through the air, but the team suspects that other factors also play a role. For example, once a vein has become damaged, the wing may dry out faster, leaving it more vulnerable to damage from even the gentlest knock, accelerating the process. Wehmann also warns researchers that they shouldn't rely on the state of an insect's wings to estimate its age: ‘the variability between wings and individuals is too great’, she explains.

Book Review

Book Review

Kinematics of wings from Caudipteryx to modern birds

This study seeks to better quantify the parameters that drove the evolution of flight from non-volant winged dinosaurs to modern birds. In order to explore this issue, we used fossil data to model the feathered forelimbs of Caudipteryx, the most basal non-volant maniraptoran dinosaur with elongated pennaceous feathers that could be described as forming proto-wings. In order to quantify the limiting flight factors, we created three hypothetical wing profiles for Caudipteryx with incrementally larger wingspans. We compared them with what revealed through fossils in wing morphology. These four models were analyzed under varying air speed, wing beat amplitude, and wing beat frequency to determine lift, thrust potential, and metabolic requirements. We tested these models using theoretical equations in order to mathematically describe the evolutionary changes observed during the evolution of modern birds from a winged terrestrial theropod like Caudipteryx. Caudipteryx could not fly, but this research indicates that with a large enough wing span, Caudipteryx-like animal could have flown. The results of these analyses mathematically confirm that during the evolution of energetically efficient powered flight in derived maniraptorans, body weight had to decrease and wing area/wing profile needed to increase together with the flapping angle and surface area for the attachment of the flight muscles. This study quantifies the morphological changes that we observe in the pennaraptoran fossil record in the overall decrease in body size in paravians, the increased wing surface area in Archaeopteryx relative to Caudipteryx, and changes observed in the morphology of the thoracic girdle, namely, the orientation of the glenoid and the enlargement of the sternum.

Flexible wings take the effort out of swimming for diving penguins

Swimming with penguins in the wild is a mind-blowing experience. When the ‘mini torpedoes’ hurtle past, you can barely make out the animals’ shape, let alone their movements. This was the problem faced by Hiroto Tanaka and colleagues from the Tokyo Institute of Technology, Japan, as they tried to understand how penguins swim; their movements are supremely swift. And even though researchers have a sense of how penguins overcome buoyancy, no one had successfully visualised how the birds use their wings to propel themselves through water; do they flap like inflexible paddles, or flex and bend as they sweep through the water? Intrigued by this mystery, Tanaka, Natsuki Harada, Takuma Oura and Masateru Maeda travelled to the Nagasaki Penguin Aquarium, Japan – home to nine species ranging in size from king penguins to little penguins – to find out how gentoo penguins (Pygoscelis papua) move beneath the waves.‘Working with real penguins at the aquarium was so exciting but demanded a lot of effort to find the appropriate setup for video recording; it took several years’, explains Tanaka, who equipped the penguins’ 4 m deep tank with up to 14 waterproof cameras trained on a rectangular region in the centre of the tank to capture their manoeuvres in 3D. Then, Harada and Oura gently attached tape markers to three points on the wings of three penguins, in addition to markers on the birds’ bellies and backs, to keep track of their motions as they plunged freely through the water. ‘I was so glad and relieved to see the penguins swim comfortably inside the measurement space’, says Tanaka, who recorded over 28 h of movies as the birds darted around the tank at speeds ranging from 0.83 to 2.07 m s−1. Then, Harada and Oura meticulously analysed the birds’ manoeuvres, identifying 40 complete wingbeats to dissect in fine detail.By dividing each wing into a lozenge shape – composed of two triangles joined at their bases, where the triangle at the wing tip could hinge up and down as the wing bent at the penguins’ wrists – to conceptualize each wing beat, the team could see that the wing tip led the penguin wing beat, bending downward (with an angle larger than –20 deg) while sweeping upward and producing a shallower upward bow (∼10 deg) as the wing swept down. Most importantly, the team recorded that the penguins surged forward during both the up- and downstrokes, accelerating more during the upstroke, in contrast to other diving birds, which accelerate more during the downstroke.But how much benefit were the penguins reaping from the flexibility of their wings? After scanning the extended right wing of a penguin, Yayi Shen (Tokyo Institute of Technology) printed a 3D model of the limb before tilting it at various angles in water flowing at 2 m s−1 to measure the lift and drag exerted on the model. Harada then used the values to calculate the forces exerted on a flat and bent wing as the penguin swam and realised that swimming with flat paddle-like wings was less efficient than when the wing bent. In other words, bending the wing reduces the amount of effort penguins have to invest in swimming, improving their efficiency.So, wing flexibility is a key component of the penguin's effortless agility, and Tanaka is eager to measure the wing motions of gentoos as they twist and turn at extremely high speeds in the aquarium. He also dreams of observing their manoeuvres in the wild, ‘but I have no idea how to do that for now’ he smiles.

High Dynamic Range in Entomological Scheimpflug Lidars

Minimizing insecticide use, preventing vector diseases and facilitating biodiversity assessments are suitable applications of recent advances in photonic insect surveillance and entomological lidar. The tools also comprise a new window into fundamental aspect of the fascinating life and ecology of insects and their predators in situ. At the same time, it is evident that lidars are subject to finite detection range given by the instrument noise and saturation levels, and therefore, intervals of the biomass spectra are sectioned at different ranges. The Scheimpflug lidar allows an interesting trade-off between high sample rate and low pulse energy for retrieving wing beat harmonics and slow sample rates with high pulse energy for detecting small species far away. In this paper, we review and revise calibration, sizing and associated deficiencies, and report count rates to 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sup> insects/minute up to 2 km range. We investigate if and how high dynamic range can be exploited in entomological lidar and also how fast and slow sample rates could complement each other and capture a wider span of the biomass spectrum. We demonstrate that smaller insect can be detected further away by long exposures and show consistency between the captured biomass size spectra. However, we find unexpected discrepancies between short and long exposures in the range distributions. We found that vertebrates as well as specular insects can saturate signals. Error sources and limitations are elaborated on.

English

The fruit fly is an invasive pest that causes significant loss in horticultural crop production by damaging the fruit quality. For the integrated management of fruit fly, monitoring is a major component. Automated pest monitoring is most promising and advanced for monitoring and accurate assessment of the status of the fruit fly. The need of the hour is to automate and monitor pest populations using advanced technologies to save time and to examine the real-time situation of the field. The purpose of this paper is to discuss the approaches and sensors which detect and monitor fruit flies automatically.The review focuses on image-based sensors for identifying fruit flies, analyzing the wing beat biometric signature with optoelectronics sensors, direct counting with photo interruption sensors and E-Traps that can provide real-time field information, and presenting the various integrated systems available.With a real-time imaging system, all information about the fruit fly population and infection rate is recorded and maintained in a database. All of this has resulted in enhanced monitoring systems for fruit fly integrated pest management.

Oxygen Dependence of Flight Performance in Ageing Drosophila melanogaster

Simple SummaryStudying insects as they age helps us better understand human ageing. Insects are excellent at delivering oxygen to flight muscles, but we do not know whether they lose their flight ability and tolerance to poor oxygen conditions with age. We studied two types of physical activity in ageing fruit flies, measuring how quickly they flap their wings and climb walls. We measured flight in either normal air or air with low oxygen availability. As we expected, young flies were better climbers than old flies, and flies flew more slowly when oxygen was low. Against expectations, young and old flies flew similarly and equally tolerated poor oxygen conditions. Overall, we suggest that insects maintain their flight abilities with age, which is surprising because insect flight requires enormous amounts of oxygen and energy. Moreover, we suggest that habitats with a poor oxygen supply (e.g., those at high elevations) can become challenging for flying insects.Similar to humans, insects lose their physical and physiological capacities with age, which makes them a convenient study system for human ageing. Although insects have an efficient oxygen-transport system, we know little about how their flight capacity changes with age and environmental oxygen conditions. We measured two types of locomotor performance in ageing Drosophila melanogaster flies: the frequency of wing beats and the capacity to climb vertical surfaces. Flight performance was measured under normoxia and hypoxia. As anticipated, ageing flies showed systematic deterioration of climbing performance, and low oxygen impeded flight performance. Against predictions, flight performance did not deteriorate with age, and younger and older flies showed similar levels of tolerance to low oxygen during flight. We suggest that among different insect locomotory activities, flight performance deteriorates slowly with age, which is surprising, given that insect flight is one of the most energy-demanding activities in animals. Apparently, the superior capacity of insects to rapidly deliver oxygen to flight muscles remains little altered by ageing, but we showed that insects can become oxygen limited in habitats with a poor oxygen supply (e.g., those at high elevations) during highly oxygen-demanding activities such as flight.

Wing damage no obstacle for hummingbird hawkmoths

It's a sad fact, but life takes its toll. From saggy skin to creaky joints, older animals build up wear and tear, and insects are no different. Over days and weeks, wings become more tattered from collisions and ageing. Yet the dogged aeronauts seem to keep going regardless, compensating for the reduction in the lift force that they can generate by beating their frayed wings faster. Yet it wasn't clear how much of an impact this deterioration might have on insect manoeuvrability. Knowing that nectar sipping hummingbird hawkmoths (Macroglossum stellatarum) must weave in sync with bobbing flowers while feasting on the sweet fluid, Anna Stöckl from University of Würzburg, Germany, with Eric Warrant and Klara Kihlström from Lund University, Sweden, decided to find out how well elderly insects with tatty wings keep up with bobbing flowers while dining.‘I went to France to collect a few adult animals and then we let them mate and raise their offspring in Sweden’, says Stöckl. Once the new adults emerged, Kihlström provided them with stands of artificial flowers to sip from when hovering, allowing some to grow old and develop tattered wings naturally, while she trimmed the wings of younger moths to simulate the effects of ageing before putting them all to the test. Fitting a motor to an artificial flower, Kihlström set the robo-bloom bobbing at speeds ranging from a gentle 11-mm-wide, 5 s long sway to frenetically bobbing back and forth 20 times per second over a narrower (0.07 mm) arc. Then she filmed the insects’ wing beats and manoeuvres as they tried to keep up. ‘We were surprised how keenly even the wing-damaged individuals approached the flowers’, says Stöckl.She and her colleagues then joined forces with Simon Sponberg and Brett Aiello from the Georgia Institute of Technology, USA, to analyse how the damage affected the moths’ movements and they were impressed to find that the moths managed to keep up even with the speediest blooms. ‘Flower tracking and manoeuvrability was not compromised by natural or artificial wing damage’, says Stöckl. However, when the researchers analysed how the impaired moths compensated for the loss of lift caused by the reduction in wing surface area, they were surprised that in addition to flapping their wings faster, the moths also swept their wings over wider arcs: they increased their wing beat amplitude. ‘A similar increase in wing beat amplitude has not been observed in any of the insect species so far studied’, says Stöckl.So why do hummingbird hawkmoths resort to this belt and braces approach to keep up with bobbing blooms when other elderly insect hoverers only beat their wings faster? The team suspects that aged hummingbird hawkmoths would have to flap their wings at rates of up to 93 flaps s–1 to compensate for their reduced wing area – a flap rate that their flight muscles are probably unable to achieve – forcing them to compensate for their lack of lift by also sweeping their wings through ever wider arcs.‘Our findings suggest that intact wings are not crucial for the precise control of lateral flight manoeuvres, which hawkmoths perform when tracking flowers within their natural movement range’, says Stöckl, adding that these moths rarely land, feeding exclusively on the wing and even laying their eggs on bobbing stickyweed when in mid-air. And the robust insects are more likely to accumulate wing damage over their lengthy lives than other species since some even hibernate over winter, making it even more essential that they maintain manoeuvrability when they emerge the following spring.

Wing damage affects flight kinematics but not flower tracking performance in hummingbird hawkmoths.

Wing integrity is crucial to the many insect species that spend distinct portions of their life in flight. How insects cope with the consequences of wing damage is therefore a central question when studying how robust flight performance is possible with such fragile chitinous wings. It has been shown in a variety of insect species that the loss in lift-force production resulting from wing damage is generally compensated by an increase in wing beat frequency rather than amplitude. The consequences of wing damage for flight performance, however, are less well understood, and vary considerably between species and behavioural tasks. One hypothesis reconciling the varying results is that wing damage might affect fast flight manoeuvres with high acceleration, but not slower ones. To test this hypothesis, we investigated the effect of wing damage on the manoeuvrability of hummingbird hawkmoths (Macroglossum stellatarum) tracking a motorised flower. This assay allowed us to sample a range of movements at different temporal frequencies, and thus assess whether wing damage affected faster or slower flight manoeuvres. We show that hummingbird hawkmoths compensate for the loss in lift force mainly by increasing wing beat amplitude, yet with a significant contribution of wing beat frequency. We did not observe any effects of wing damage on flight manoeuvrability at either high or low temporal frequencies.

The presence of knockdown resistance mutations reduces male mating competitiveness in the major arbovirus vector, Aedes aegypti.

The development of insecticide resistance in mosquitoes can have pleiotropic effects on key behaviours such as mating competition and host-location. Documenting these effects is crucial for understanding the dynamics and costs of insecticide resistance and may give researchers an evidence base for promoting vector control programs that aim to restore or conserve insecticide susceptibility. We evaluated changes in behaviour in a backcrossed strain of Aedes aegypti, homozygous for two knockdown resistance (kdr) mutations (V1016G and S989P) isolated in an otherwise fully susceptible genetic background. We compared biting activity, host location behaviours, wing beat frequency (WBF) and mating competition between the backcrossed strain, and the fully susceptible and resistant parental strains from which it was derived. The presence of the homozygous kdr mutations did not have significant effects on blood avidity, the time to locate a host, or WBF in females. There was, however, a significant reduction in mean WBF in males and a significant reduction in estimated male mating success (17.3%), associated with the isolated kdr genotype. Our results demonstrate a cost of insecticide resistance associated with an isolated kdr genotype and manifest as a reduction in male mating success. While there was no recorded difference in WBF between the females of our strains, the significant reduction in male WBF recorded in our backcrossed strain might contribute to mate-recognition and mating disruption. These consequences of resistance evolution, especially when combined with other pleiotropic fitness costs that have been previously described, may encourage reversion to susceptibility in the absence of insecticide selection pressures. This offers justification for the implementation of insecticide resistance management strategies based on the rotation or alternation of different insecticide classes in space and time.

Design and kinematic analysis of flapping wing mechanism for common swift inspired micro aerial vehicle

The article presents a novel flapping wing mechanism for Micro Aerial Vehicle (MAV) inspired by one of the most efficient flyers of the aerial world, the Common swift ( Apus apus). The flight characteristics such as wing beat frequency, wing beat amplitude, and fore and aft movements, as well as wing rotation of the bird at a flight speed 8 m /s, were studied. The common swift rotates its hand wing keeping the pitch of the arm wing constant during the entire wingbeat cycle. The hand wing undergoes forward rotation during the downstroke and backward rotation during the upstroke. This complex wing kinematics enables swift to generate various unsteady aerodynamic mechanisms. Using the geometric and kinematic details, a flapping wing mechanism that emulates the wing kinematics of the bird was designed. The flapping wing mechanism based on the epicyclic ellipsograph mechanism presented herein integrates flapping motion, fore and aft motion, and selective wing rotation. Importantly, this fully constrained mechanism allows performing all the key kinematic motions of the common swift with a single actuator. A kinematic model of the mechanism is presented to calculate the design parameters based on the scale of the MAV. Kinematic simulation of the mechanism is also presented to verify the design.