Wing Beat Research Articles

A Flight Sensory-Motor to Olfactory Processing Circuit in the Moth Manduca sexta.

Neural circuits projecting information from motor to sensory pathways are common across sensory domains. These circuits typically modify sensory function as a result of motor pattern activation; this is particularly so in cases where the resultant behavior affects the sensory experience or its processing. However, such circuits have not been observed projecting to an olfactory pathway in any species despite well characterized active sampling behaviors that produce reafferent mechanical stimuli, such as sniffing in mammals and wing beating in the moth Manduca sexta. In this study we characterize a circuit that connects a flight sensory-motor center to an olfactory center in Manduca. This circuit consists of a single pair of histamine immunoreactive (HA-ir) neurons that project from the mesothoracic ganglion to innervate a subset of ventral antennal lobe (AL) glomeruli. Furthermore, within the AL we show that the M. sexta histamine B receptor (MsHisClB) is exclusively expressed by a subset of GABAergic and peptidergic LNs, which broadly project to all olfactory glomeruli. Finally, the HA-ir cell pair is present in fifth stage instar larvae; however, the absence of MsHisClB-ir in the larval antennal center indicates that the circuit is incomplete prior to metamorphosis and importantly prior to the expression of flight behavior. Although the functional consequences of this circuit remain unknown, these results provide the first detailed description of a circuit that interconnects an olfactory system with motor centers driving flight behaviors including odor-guided flight.

Bizarre snail that swims like a flying insect

Snails usually lumber along on their single fleshy foot, but not sea butterflies (Limacina helicina). These tiny marine molluscs gently flit around their Arctic water homes propelled by fleshy wings that protrude out of the shell opening. But little was known about how they move through water. ‘Most zooplankton swim with a drag-based paddling technique,’ explains David Murphy from the Georgia Institute of Technology, USA, and even though one of Murphy's thesis advisors – Jeannette Yen – had filmed one of the enigmatic snails swimming while it was attached to a wire in 2003, it had not been possible to observe how fluid flowed around the animals to explain how they move. So, when Murphy built a new 3D system to visualise fluid movements around minute animals, Yen and Don Webster were keen to test more sea butterflies as they swam freely to discover more about their exotic mode of propulsion.However, working with the delicate animals in land-locked Atlanta posed a unique set of challenges. Murphy explains that sea butterflies are scarce at the best of times, and that transporting the fragile gelatinous creatures across the continent from their ocean home was tricky. ‘You have to ship them overnight in an insulated cooler to keep them cold and if the water is too dirty, particles will stick to them, so the water has to be very clean’, he says. Yen then devised a cunning V-shaped structure at the bottom of the tank to ensure that the freely swimming snails repeatedly ascended through the middle portion of the tank – where four high-speed cameras were focused to capture every detail of the wings’ movements. Even then, Murphy admits that it was a miracle that they were able to collect any data, and he recalls that the team only had a few short hours to film the molluscs, explaining that they could only be sure that the swimming conditions were ideal then. However, by the end of the afternoon the snails had serendipitously crossed the path of the cameras on four occasions. ‘In this sort of free-swimming experiment, it's normal to take 30 passes to get three usable ones, but we got really lucky! The animals even cooperated by swimming in different orientations, so we could see different perspectives’, chuckles Murphy, who then began visualising the snails' wing beats and the fluid movements around their bodies with Deepak Adhikari.After months of painstaking analysis – interrupted by Murphy's relocation from Georgia to Johns Hopkins University in Baltimore, Maryland – the team was astonished when they realised that the snails were swimming just like fruit flies fly. ‘I said to myself, “Its wing stroke is just like what an insect is doing”’, recalls Murphy, describing the snails’ characteristic figure-of-eight wing beat that was only apparent after he took account of the molluscs’ extraordinary bobbing motion. And when he investigated how water flowed around the snails’ wings, he was impressed to see that the molluscs generated the same low-pressure system that produces lift in flying fruit flies. Murphy explains that the snails (and fruit flies) clap their wings together at the top of a wing beat before peeling them apart, sucking fluid into the V-shaped gap between the wings to create low-pressure vortices at the wing tips that generate lift. He says, ‘No one has actually been able to measure the flow around an insect doing this while it is flying, and so that was kind of the holy grail of this area of research’. And he adds, ‘It really surprised me that sea butterflies turned out to be honorary insects’.

European shags optimize their flight behavior according to wind conditions.

Aerodynamics results in two characteristic speeds of flying birds: the minimum power speed and the maximum range speed. The minimum power speed requires the lowest rate of energy expenditure per unit time to stay airborne and the maximum range speed maximizes air distance traveled per unit of energy consumed. Therefore, if birds aim to minimize the cost of transport under a range of wind conditions, they are predicted to fly at the maximum range speed. Furthermore, take-off is predicted to be strongly affected by wind speed and direction. To investigate the effect of wind conditions on take-off and cruising flight behavior, we equipped 14 European shags Phalacrocorax aristotelis with a back-mounted GPS logger to measure position and hence ground speed, and a neck-mounted accelerometer to record wing beat frequency and strength. Local wind conditions were recorded during the deployment period. Shags always took off into the wind regardless of their intended destination and take-off duration was correlated negatively with wind speed. We combined ground speed and direction during the cruising phase with wind speed and direction to estimate air speed and direction. Whilst ground speed was highly variable, air speed was comparatively stable, although it increased significantly during strong head winds, because of stronger wing beats. The increased air speeds in head winds suggest that birds fly at the maximum range speed, not at the minimum power speed. Our study demonstrates that European shags actively adjust their flight behavior to utilize wind power to minimize the costs of take-off and cruising flight.

Shags take advantage of headwind to take off

During the nesting season, the pressure is on for avian mums and dads to provide as much nourishment as possible for their chicks. For seabird parents, this can mean costly foraging trips across the waves. Katsufumi Sato from the University of Tokyo, Japan, explains that it was thought that seabirds may improve their flight cost efficiency by flying into headwinds to increase their air speed (the speed relative to the prevailing wind). However, it was not known whether birds actively choose to fly into the wind to reduce their costs and few studies had recorded seabird flights in enough detail to find out whether the seabirds take advantage of headwinds. So, Sato and his colleagues Yukihisa Kogure and Yutaka Watanuki added tiny accelerometers to the new generation of lightweight GPS tracking systems, which enabled them to use the equipment to follow foraging seabird flights with sufficient accuracy to assess whether the wind helps improve their efficiency.Travelling to Scotland to work with long-term collaborators Francis Daunt and Sarah Wanless from the Centre for Ecology & Hydrology, UK, Sato and his colleagues were ready to track the flights of foraging European shags. Over three consecutive breeding seasons, the scientists caught the boat to the Isle of May off Scotland where they carefully attached accelerometers and GPS trackers to the necks and backs of 14 male shags before returning the birds to their nests. Then, having measured the wind speed at the highest point on the island and after successfully retrieving the data loggers, Sato and Kogure were faced with the gargantuan task of reconstructing the bird flight paths from thousands of GPS coordinates, in addition to measuring the birds' wing beat patterns from the acceleration traces, before calculating the birds' flight and air speeds.Having analysed 147 flights, Sato and Kogure could see that the birds flapped their wings harder during take-off from the water than when cruising through the air, suggesting that they were expending more energy as they became airborne. Also, all of the birds took off into a headwind regardless of their final destination, to take advantage of the lift generated by the wind rushing towards them. And on two occasions – when the wind speed was in excess of 8 m s−1 – the birds were able to become airborne without the usual exertions by simply flapping their wings as if they were cruising.However, once they were aloft, the wind direction seemed to have little effect on the shags' choice of course, with the birds flying in all possible directions. And when the team estimated the birds' air speed, by subtracting the wind speed from the ground speed, they found that it was relatively stable at around 15 m s−1, unless the birds were flying into a strong headwind, when they flapped their wings harder and increased their air speed. The team suspects that instead of flying at the lowest power that allows them to remain aloft, European shags fly at a speed that allows them to travel the greatest distance for the least energy consumed during the flight. They also suggest that the birds are able to adjust their flight strategy to take the greatest advantage of any assistance that the wind can give them. However, they warn that the stronger winds that are predicted as a consequence of climate change could have beneficial and detrimental effects on foraging shags, giving the birds a helping hand to take off while hampering them as they battle headwinds once airborne.

Realistic Instrumentation Platform for Active and Passive Optical Remote Sensing.

We describe the development of a novel versatile optical platform for active and passive remote sensing of environmental parameters. Applications include assessment of vegetation status and water quality. The system is also adapted for ecological studies, such as identification of flying insects including agricultural pests. The system is based on two mid-size amateur astronomy telescopes, continuous-wave diode lasers at different wavelengths ranging from violet to the near infrared, and detector facilities including quadrant photodiodes, two-dimensional and line scan charge-coupled device cameras, and a compact digital spectrometer. Application examples include remote Ramanlaser-induced fluorescence monitoring of water quality at 120 m distance, and insect identification at kilometer ranges using the recorded wing beat frequency and its spectrum of overtones. Because of the low cost this developmental platform is very suitable for advanced research projects in developing countries and has, in fact, been multiplied during hands-on workshops and is now being used by a number of groups at African universities.

Intra-specific variation in wing morphology and its impact on take-off performance in blue tits (Cyanistes caeruleus) during escape flights.

ABSTRACTDiurnal and seasonal increases in body mass and seasonal reductions in wing area may compromise a bird's ability to escape, as less of the power available from the flight muscles can be used to accelerate and elevate the animal's centre of mass. Here, we investigated the effects of intra-specific variation in wing morphology on escape take-off performance in blue tits (Cyanistes caeruleus). Flights were recorded using synchronised high-speed video cameras and take-off performance was quantified as the sum of the rates of change of the kinetic and potential energies of the centre of mass. Individuals with a lower wing loading, WL (WL=body weight/wing area) had higher escape take-off performance, consistent with the increase in lift production expected from relatively larger wings. Unexpectedly, it was found that the total power available from the flight muscles (estimated using an aerodynamic analysis) was inversely related to WL. This could simply be because birds with a higher WL have relatively smaller flight muscles. Alternatively or additionally, variation in the aerodynamic load on the wing resulting from differences in wing morphology will affect the mechanical performance of the flight muscles via effects on the muscle's length trajectory. Consistent with this hypothesis is the observation that wing beat frequency and relative downstroke duration increase with decreasing WL; both are factors that are expected to increase muscle power output. Understanding how wing morphology influences take-off performance gives insight into the potential risks associated with feather loss and seasonal and diurnal fluctuations in body mass.

Batoid locomotion: effects of speed on pectoral fin deformation in the little skate, Leucoraja erinacea.

Most batoids have a unique swimming mode in which thrust is generated by either oscillating or undulating expanded pectoral fins that form a disc. Only one previous study of the freshwater stingray has quantified three-dimensional motions of the wing, and no comparable data are available for marine batoid species that may differ considerably in their mode of locomotion. Here, we investigate three-dimensional kinematics of the pectoral wing of the little skate, Leucoraja erinacea, swimming steadily at two speeds [1 and 2bodylengths(BL)s-1]. We measured the motion of nine points in three dimensions during wing oscillation and determined that there are significant differences in movement amplitude among wing locations, as well as significant differences as speed increases in body angle, wing beat frequency and speed of the traveling wave on the wing. In addition, we analyzed differences in wing curvature with swimming speed. At 1 BL s-1, the pectoral wing is convex in shape during the downstroke along the medio-lateral fin midline, but at 2 BL s-1 the pectoral fin at this location cups into the flow, indicating active curvature control and fin stiffening. Wing kinematics of the little skate differed considerably from previous work on the freshwater stingray, which does not show active cupping of the whole fin on the downstroke.

Mulberries, and: The Old Lady Tour

Mulberries, and: The Old Lady Tour Donald Platt (bio) Mulberries For breakfast I go out and eat mulberries straight from the tree. I cram them into my hungry watering mouth, so succulent sweet, crunch of their star seeds between my teeth. If one could eat the infinite night sky, it would taste like plump mulberries. They start out small, light green, almost white, swell to pink drupelets, then turn to blood clots, ripen black. Plucked red, they’re tart. Pick them too late, and they’ve already begun to ferment. Dark sugars fester in my mouth. Festina lente, make haste slowly, say the old Latin writers. Such sweet paradox, delicious to the tongue as rain-swollen mulberries. Learn how to grow old and die from them. By tomorrow, some of the red berries will have turned to black constellations I’ll reach for. The starlings will gorge on them, shit out mid mind-maddening zigzag flight [End Page 28] their purple-splatter Rorschachs, a diarrhea diary on our white car’s roof and hood. I read my future in that screed. Festina lente. The world’s a festival of lights. The coreopsis’s bright sunspots will wilt and black out slowly if summer brings no withering drought on the red-winged blackbird’s quick apocalyptic wing. It flashes fire and night with each dark wing beat’s hammer stroke and strike. Death, make haste slowly. Away let me idle this day. A white, two-seater plane buzzes above me, banks, practices perfect circles, pollinates the cumulus clouds flowering the southeast horizon—pure white, hybrid peonies. When I was young, an old poet told me that the proper subject of poetry was flowers. What a forty-pound sack of horse manure, I thought. Now, I’m not so sure. Our hostas put forth green spikes whose tips erupt into creamy lavender clusters of florets, summer’s erectile tissue. The backyard’s studded with clover, star field of weeds that take over everything. Cool breeze sways the mulberry tree. I’m happy to waste my life on these words, so many indescribably sweet mulberries [End Page 29] that I and the gossipy starlings can’t possibly consume them all. They fall to the ground where they too become black dirt. The Old Lady Tour Dana, my wife, used to drive her dad, Erwin, from his retirement community in Virginia Beach to visit his two lifelong friends three hours away in Charlottesville. “The old lady tour” she calls it, as if Coco and Carter are landmarks, bronze nonagenarian statues that the pigeons perch and shit upon in the city square, each with a tarnished plaque identifying them, their dates, the exploits that made them famous under the dumbstruck sun now petrified to a standstill. Erwin’s dead. We still make the rounds, do the old lady tour. Coco, who started out in independent living fifteen years ago, just moved to a single room next to the solarium on the third floor of the nursing home. “The waiting for God floor” she likes to call it at ninety-four. She launches into her monologue. How her good friend, who ended up a baroness, was “barren, [End Page 30] no kids” and had gotten married three times. “The first marriage was for love, the second for money, the third for sex.” Coco too is childless. She shows us photos of herself and her late husband Horace in front of their black Bentley in the early 1950s. She looks like a movie star in her form-fitting, strapless, silver satin dress. Her now-thinning white hair, wild as Einstein’s, was then platinum blonde and permed in synchronized waves. She and Horace, in his dove-gray morning suit, were “the cream of Charlottesville’s horsey set.” She tells us how they built an ultra-modern house out in the country, mostly glass, with floor-to-ceiling windows, against which the hounds when Horace went riding with their neighbors in the monthly fox hunt “would lift their legs” as they went baying by, hot on the scent. Coco would have to go out and wash the windows. The couple to whom she sold the property tore the...

Concept of an Active Amplification Mechanism in the Infrared Organ of Pyrophilous Melanophila Beetles

Jewel beetles of the genus Melanophila possess a pair of metathoracic infrared (IR) organs. These organs are used for forest fire detection because Melanophila larvae can only develop in fire killed trees. Several reports in the literature and a modeling of a historic oil tank fire suggest that beetles may be able to detect large fires by means of their IR organs from distances of more than 100 km. In contrast, the highest sensitivity of the IR organs, so far determined by behavioral and physiological experiments, allows a detection of large fires from distances up to 12 km only. Sensitivity thresholds, however, have always been determined in non-flying beetles. Therefore, the complete micromechanical environment of the IR organs in flying beetles has not been taken into consideration. Because the so-called photomechanic sensilla housed in the IR organs respond bimodally to mechanical as well as to IR stimuli, it is proposed that flying beetles make use of muscular energy coupled out of the flight motor to considerably increase the sensitivity of their IR sensilla during intermittent search flight sequences. In a search flight the beetle performs signal scanning with wing beat frequency while the inputs of the IR organs on both body sides are compared. By this procedure the detection of weak IR signals could be possible even if the signals are hidden in the thermal noise. If this proposed mechanism really exists in Melanophila beetles, their IR organs could even compete with cooled IR quantum detectors. The theoretical concept of an active amplification mechanism in a photon receptor innervated by highly sensitive mechanoreceptors is presented in this article.

Bats coordinate echolocation calls with wing beats

![Figure][1] Big brown bat negotiating net obstacle. Photo credit: Ben Falk. Bats are the ultimate evolutionary opportunists. To cash in on the bonanza of insects that take to the air after dark, the mammals have developed agile flight and a unique echolocation system to locate fast-moving

"Singing in the Tube"--audiovisual assay of plant oil repellent activity against mosquitoes (Culex pipiens).

Plant essential oils have been suggested as a promising alternative to the established mosquito repellent DEET (N,N-diethyl-meta-toluamide). Searching for an assay with generally available equipment, we designed a new audiovisual assay of repellent activity against mosquitoes "Singing in the Tube," testing single mosquitoes in Drosophila cultivation tubes. Statistics with regression analysis should compensate for limitations of simple hardware. The assay was established with female Culex pipiens mosquitoes in 60 experiments, 120-h audio recording, and 2580 estimations of the distance between mosquito sitting position and the chemical. Correlations between parameters of sitting position, flight activity pattern, and flight tone spectrum were analyzed. Regression analysis of psycho-acoustic data of audio files (dB[A]) used a squared and modified sinus function determining wing beat frequency WBF ± SD (357 ± 47Hz). Application of logistic regression defined the repelling velocity constant. The repelling velocity constant showed a decreasing order of efficiency of plant essential oils: rosemary (Rosmarinus officinalis), eucalyptus (Eucalyptus globulus), lavender (Lavandula angustifolia), citronella (Cymbopogon nardus), tea tree (Melaleuca alternifolia), clove (Syzygium aromaticum), lemon (Citrus limon), patchouli (Pogostemon cablin), DEET, cedar wood (Cedrus atlantica). In conclusion, we suggest (1) disease vector control (e.g., impregnation of bed nets) by eight plant essential oils with repelling velocity superior to DEET, (2) simple mosquito repellency testing in Drosophila cultivation tubes, (3) automated approaches and room surveillance by generally available audio equipment (dB[A]: ISO standard 226), and (4) quantification of repellent activity by parameters of the audiovisual assay defined by correlation and regression analyses.

Automatic classification of flying bird species using computer vision techniques

Bird populations are identified as important biodiversity indicators, so collecting reliable population data is important to ecologists and scientists. However, existing manual monitoring methods are labour-intensive, time-consuming, and potentially error prone. The aim of our work is to develop a reliable automated system, capable of classifying the species of individual birds, during flight, using video data. This is challenging, but appropriate for use in the field, since there is often a requirement to identify in flight, rather than while stationary. We present our work, which uses a new and rich set of appearance features for classification from video. We also introduce motion features including curvature and wing beat frequency. Combined with Normal Bayes classifier and a Support Vector Machine classifier, we present experimental evaluations of our appearance and motion features across a data set comprising seven species. Using our appearance feature set alone we achieved a classification rate of 92% and 89% (using Normal Bayes and SVM classifiers respectively) which significantly outperforms a recent comparable state-of-the-art system. Using motion features alone we achieved a lower-classification rate, but motivate our on-going work which we seeks to combine these appearance and motion feature to achieve even more robust classification.

Skipper genome sheds light on unique phenotypic traits and phylogeny.

BackgroundButterflies and moths are emerging as model organisms in genetics and evolutionary studies. The family Hesperiidae (skippers) was traditionally viewed as a sister to other butterflies based on its moth-like morphology and darting flight habits with fast wing beats. However, DNA studies suggest that the family Papilionidae (swallowtails) may be the sister to other butterflies including skippers. The moth-like features and the controversial position of skippers in Lepidoptera phylogeny make them valuable targets for comparative genomics.ResultsWe obtained the 310 Mb draft genome of the Clouded Skipper (Lerema accius) from a wild-caught specimen using a cost-effective strategy that overcomes the high (1.6 %) heterozygosity problem. Comparative analysis of Lerema accius and the highly heterozygous genome of Papilio glaucus revealed differences in patterns of SNP distribution, but similarities in functions of genes that are enriched in non-synonymous SNPs. Comparison of Lepidoptera genomes revealed possible molecular bases for unique traits of skippers: a duplication of electron transport chain components could result in efficient energy supply for their rapid flight; a diversified family of predicted cellulases might allow them to feed on cellulose-enriched grasses; an expansion of pheromone-binding proteins and enzymes for pheromone synthesis implies a more efficient mate-recognition system, which compensates for the lack of clear visual cues due to the similarities in wing colors and patterns of many species of skippers. Phylogenetic analysis of several Lepidoptera genomes suggested that the position of Hesperiidae remains uncertain as the tree topology varied depending on the evolutionary model.ConclusionCompletion of the first genome from the family Hesperiidae allowed comparative analyses with other Lepidoptera that revealed potential genetic bases for the unique phenotypic traits of skippers. This work lays the foundation for future experimental studies of skippers and provides a rich dataset for comparative genomics and phylogenetic studies of Lepidoptera.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-015-1846-0) contains supplementary material, which is available to authorized users.

Towards Quantitative Optical Cross Sections in Entomological Laser Radar - Potential of Temporal and Spherical Parameterizations for Identifying Atmospheric Fauna.

In recent years, the field of remote sensing of birds and insects in the atmosphere (the aerial fauna) has advanced considerably, and modern electro-optic methods now allow the assessment of the abundance and fluxes of pests and beneficials on a landscape scale. These techniques have the potential to significantly increase our understanding of, and ability to quantify and manage, the ecological environment. This paper presents a concept whereby laser radar observations of atmospheric fauna can be parameterized and table values for absolute cross sections can be catalogued to allow for the study of focal species such as disease vectors and pests. Wing-beat oscillations are parameterized with a discrete set of harmonics and the spherical scatter function is parameterized by a reduced set of symmetrical spherical harmonics. A first order spherical model for insect scatter is presented and supported experimentally, showing angular dependence of wing beat harmonic content. The presented method promises to give insights into the flight heading directions of species in the atmosphere and has the potential to shed light onto the km-range spread of pests and disease vectors.

Dynamics of Cricket Sound Production

The clever designs of natural transducers are a great source of inspiration for man-made systems. At small length scales, there are many transducers in nature that we are now beginning to understand and learn from. Here, we present an example of such a transducer that is used by field crickets to produce their characteristic song. This transducer uses two distinct components—a file of discrete teeth and a plectrum that engages intermittently to produce a series of impulses forming the loading, and an approximately triangular membrane, called the harp, that acts as a resonator and vibrates in response to the impulse-train loading. The file-and-plectrum act as a frequency multiplier taking the low wing beat frequency as the input and converting it into an impulse-train of sufficiently high frequency close to the resonant frequency of the harp. The forced vibration response results in beats producing the characteristic sound of the cricket song. With careful measurements of the harp geometry and experimental measurements of its mechanical properties (Young's modulus determined from nanoindentation tests), we construct a finite element (FE) model of the harp and carry out modal analysis to determine its natural frequency. We fine tune the model with appropriate elastic boundary conditions to match the natural frequency of the harp of a particular species—Gryllus bimaculatus. We model impulsive loading based on a loading scheme reported in literature and predict the transient response of the harp. We show that the harp indeed produces beats and its frequency content matches closely that of the recorded song. Subsequently, we use our FE model to show that the natural design is quite robust to perturbations in the file. The characteristic song frequency produced is unaffected by variations in the spacing of file-teeth and even by larger gaps. Based on the understanding of how this natural transducer works, one can design and fabricate efficient microscale acoustic devices such as microelectromechanical systems (MEMS) loudspeakers.

Wings as a new route of exposure to pesticides in the honey bee.

In pesticide risk assessment, estimating the routes and levels of exposure is critical. For honey bees subjected to pesticide spray, toxicity is assessed by thorax contact to account for all possible contact exposures. In the present study, the authors tested 6 active substances with different hydrophobicity. For the first time, the authors demonstrated that it is possible to induce mortality by pesticide contact with only the wings of the honey bee. The toxicities induced by contact with the wings and thorax were similar, with the wing median lethal dose (LD50) being 0.99 to 2.23 times higher than that of the thorax. This finding demonstrates that the wings represent a relevant route of exposure in the honey bee. In a second approach, the authors estimated the air volume displaced by the wings during 1 beating cycle to be 0.51 ± 0.03 cm(3), which corresponds to a volume of 116.8 ± 5.8 cm(3) s(-1) at a wing beat frequency of 230 Hz. The authors then tested realistic scenarios of exposure for bees flying through a pesticide cloud at different concentrations. In the worst-case scenario, the dose accumulated during the flight reached 525 ng bee(-1) s(-1). These results show that the procedure used to assess the risk posed by contact with pesticides could be improved by accounting for wing exposure.

Antennal mechanosensory neurons mediate wing motor reflexes in flying Drosophila.

Although many behavioral studies have shown the importance of antennal mechanosensation in various aspects of insect flight control, the identities of the mechanosensory neurons responsible for these functions are still unknown. One candidate is the Johnston's organ (JO) neurons that are located in the second antennal segment and detect phasic and tonic rotations of the third antennal segment relative to the second segment. To investigate how different classes of JO neurons respond to different types of antennal movement during flight, we combined 2-photon calcium imaging with a machine vision system to simultaneously record JO neuron activity and the antennal movement from tethered flying fruit flies (Drosophila melanogaster). We found that most classes of JO neurons respond strongly to antennal oscillation at the wing beat frequency, but not to the tonic deflections of the antennae. To study how flies use input from the JO neurons during flight, we genetically ablated specific classes of JO neurons and examined their effect on the wing motion. Tethered flies flying in the dark require JO neurons to generate slow antiphasic oscillation of the left and right wing stroke amplitudes. However, JO neurons are not necessary for this antiphasic oscillation when visual feedback is available, indicating that there are multiple pathways for generating antiphasic movement of the wings. Collectively, our results are consistent with a model in which flying flies use JO neurons to detect increases in the wing-induced airflow and that JO neurons are involved in a response that decreases contralateral wing stoke amplitude.

Use of acoustic signals in mating in an eavesdropping frog-biting midge

The sensory systems of organisms are shaped by selective pressures imposed by their performance in a variety of contexts. Female frog-biting midges use the mating calls of anurans to locate their host to obtain a blood meal. Although the use of sound in foraging is well documented in this group, it is unknown whether sound is used in other contexts. To investigate the ability to use sound in nonforaging contexts, we experimentally tested the prediction that frog-biting midges (Corethrella appendiculata) use sound in mating. We recorded their wing beats while swarming, in controlled tethered conditions and during different- and same-sex pair interactions. Our results show sexual differences in the acoustic properties of flight tones, with male midges having higher frequency wing beats than females. Wing beats of free-flying individuals were significantly higher in frequency than those recorded from tethered individuals, cautioning the interpretation of recordings obtained following this widely used technique. In addition, interacting, tethered opposite-sex pairs altered their flight tones to match their upper harmonics, converging at the third and fourth harmonic frequencies of males and females, respectively. In male–male interactions, however, the frequency of their wing beats diverged. Therefore, flight tones in frog-biting midges may function as courtship signals attracting conspecific females and deterring rival males. We discuss the use of sound in multiple contexts in these midges and potential factors leading to their ability to eavesdrop on anurans.

Pigeons trade efficiency for stability in response to level of challenge during confined flight

Individuals traversing challenging obstacles are faced with a decision: they can adopt traversal strategies that minimally disrupt their normal locomotion patterns or they can adopt strategies that substantially alter their gait, conferring new advantages and disadvantages. We flew pigeons (Columba livia) through an array of vertical obstacles in a flight arena, presenting them with this choice. The pigeons selected either a strategy involving only a slight pause in the normal wing beat cycle, or a wings-folded posture granting reduced efficiency but greater stability should a misjudgment lead to collision. The more stable but less efficient flight strategy was not used to traverse easy obstacles with wide gaps for passage but came to dominate the postures used as obstacle challenge increased with narrower gaps and there was a greater chance of a collision. These results indicate that birds weigh potential obstacle negotiation strategies and estimate task difficulty during locomotor pattern selection.

High frequency and counterstroking:Calopteryx splendensfemale threatening flight

A hitherto unknown flight pattern of female Calopteryx splendens is described. On a day with heavy winds, when no damselfly could fly in open space of the river, I observed and filmed four to six females foraging in a small bay sheltered by bank vegetation. Females fought for perches and showed a threatening flight with counterstroking and high frequency wing-beating. In all other female flight modes the fore and hind wings were beaten nearly in parallel with a much lower beat frequency. As the newly observed flight mode resembles the courting flight mode of males of C. splendens the female's threatening flight is compared with it. At landings of both sexes the wings were beaten in a counterstroking mode for one to seven beats, as well. The possible development of female's threatening flight from wing beating during landing of C. splendens is discussed. The relevance of these findings is to extend the knowledge about the variety of flight modes in Calopteryx females.