The effect of forewing depressor activity on wing movement during locust flight

Locusts are passively yawed in the laminar air current of a wind tunnel (Fig. 1). In order to study the influence of depressor muscles of the forewing on its movement, electromyography is combined with true 3-dimensional inductive forewing movement recording. In quick response to the yaw stimulus, many kinematic parameters (e.g. shape of the wing tip path, amplitudes of wingstroke, ratios of downstroke to upstroke duration, time interval between beginning of downstroke and time of maximum pronation etc.) vary differently in both forewings (Figs. 3–5). Pronation changes in correlation to yawing reciprocally on both forewings with comparable differences of pronation angles (Fig. 5a). Maximum pronation is decreased on that side, to which the animal is-passively-yawed, whereas the slope of the wing tip paths remains almost constant. Therefore, decreasing pronation most probably indicates increasing thrust. The animal appears to perform a disturbance avoidance behaviour. Although the burst length of muscle firing is almost constant here, the onset of 8 depressor muscles (1 st basalar and subalar muscles of all 4 wings) varies in correlation to the stimulus (Figs. 6–8). The changing time intervals between the 1 st basalar muscle M97 and subalar muscle M99 are responsible for the alterations of forewing downstroke. Quantitative analysis of combined motor and movement pattern (Fig. 9) shows the following: (i) the maximum pronation and time interval between the onset of 1 st basalar muscle M97 as well as subalar muscle M99 and the beginning of downstroke are positively correlated (Figs. 10 and 12a and b). (ii) Maximum pronation is greatest, when muscles M97 and M99 act simultaneously (Fig. 12c). Thus, both muscles work synergistically, concerning pronation. Muscle M99 is of less importance than muscle M97. On failing activity of the depressor muscle M97, downstroke is greatly reduced. Some depressor as well as elevator muscles are switched on and off separately on each side (Fig. 11).     

The motor pattern of locusts during visually induced rolling in long-term flight

Desert locusts (Schistocerca gregaria F.), mounted in a wind tunnel on a low-mechanical-impedance torque meter, flew for at least 30 min in the posture typical of long-term flight. As they flew, they were induced to rotate about their long axis (roll) by rotation of an artificial horizon. All maintained departures from the horizontal attitude were brought about actively, by the animal's own efforts. In the roll maneuver, the hindlegs and abdomen were bent toward the side ipsilateral to the direction of rotation. However, these rudderlike movements were not adequate to initiate and maintain a constant roll angle.During a roll, there was a change in the pattern of excitation of all the wing muscles that were monitored: the depressorsM81, 97, 99, 112, 127, and 129, and the elevatorsM83, 84, 89, 113, 118, 119 (numbering according to Snodgrass 1929). Hence all 12 muscles probably not only provide power for the flight but also steer it. Evidently, then, for these muscles a rigid distinction between power and steering muscles is not appropriate.The period of the contraction cycle changed in correlation with the roll angle, but was not a parameter for control of the roll maneuver, because the changes were the same in all muscles (Fig. 2).Even with constant burst length, the phase shifts between the muscles changed. These changes were the main control parameter for rolling (Figs. 3–9).There was a latency coupling between elevators and the following depressors (Fig. 3).The changes in phase shift were tonic or phasic (sometimes phasic-tonic) in different muscle pairs (Fig. 4).When a roll angle of ca. 15° was adopted, the phase shifts between depressor muscles in a given fore- or hindwing (e.g.,M127R vs.M129R) changed by about 5 ms, whereas the elevators changed by less than 1 ms (Fig. 6).The phase shifts between the anterior elevators and depressors of a given wing, as well as the posterior elevators and depressors, changed by ca. 5 ms (in some cases with different time courses) when the animal rolled to an angle of ca. 15° (Fig. 7).The changes in phase shift between muscles of the fore-and hindwing on one side of the body amounted, as a rule, to about 4 ms at ca. 15° roll (Fig. 8).Corresponding muscles on the two sides of the body change in phase with respect to one another by as much as 10 ms (Fig. 9). The phase shifts of all such contralateral muscle pairs except for the posterior basalar muscles,M127, have the same sign, such that the muscle ipsilateral to the direction of rotation becomes active sooner.     

Flight motor patterns of locusts responding to thermal stimuli

Correctional and intentional steering manoeuvres in locusts differ in several important respects. The most profound difference between the two is the production of large forewing asymmetries in angle of elevation during the downstroke in intentional steering that are not obvious in correctional steering. We investigated the flight motor patterns during intentional steering responses to a radiant heat source. We found asymmetries in the timing of forewing first basalar (m97) activity on the left and right sides that were strongly and positively correlated with forewing asymmetries. Timing asymmetry in the second basalar (m98) and pleuroalar (m85) muscles was not significantly different from the changes observed in m97. The hindwing first basalar (m127) shifted its asymmetry in the opposite direction. The forewing subalar muscle (m99) did not shift its asymmetry with the same magnitude as m97, but instead was phase-shifted relative to m97 on the left and right sides, suggesting its role as a supinator. We conclude that large asymmetries in the elevation angle of the forewings during the downstroke, as are evident in intentional steering, are generated by bulk shifts in the activation times of forewing depressor muscles to cause a relative shift in the time of stroke reversals of the two forewings. Accepted: 19 June 1998     

Visual control of steering in locust flight: the effects of head movement on responses to roll stimuli

The contribution of head movement to the control of roll responses in flying locusts (Locusta migratoria) has been examined (i) on a flight balance, recording the angles through which the locust turns when following an artificial horizon; (ii) by recording activity in a pair of flight muscles in restrained conditions; and (iii) by observations on free flying locusts. Responses were compared when the head was free to turn about the thorax, as normal, and when the head was waxed to the thorax, blocking any relative motion between the two (head-fixed). These experiments suggest that the major signal generating corrective roll manoeuvres is the visual error between the angle of the head and the horizon, rather than a signal that includes a measure of the head-thorax angle.

Acoustic startle/escape reactions in tethered flying locusts: motor patterns and wing kinematics underlying intentional steering

We simultaneously recorded flight muscle activity and wing kinematics in tethered, flying locusts to determine the relationship between asymmetric depressor muscle activation and the kinematics of the stroke reversal at the onset of wing depression during attempted intentional steering manoeuvres. High-frequency, pulsed sounds produced bilateral asymmetries in forewing direct depressor muscles (M97, 98, 99) that were positively correlated with asymmetric forewing depression and asymmetries in stroke reversal timing. Bilateral asymmetries in hindwing depressor muscles (M127 and M128 but not M129) were positively correlated with asymmetric hindwing depression and asymmetries in the timing of the hindwing stroke reversal; M129 was negatively correlated with these shifts. Hindwing depressor asymmetries and wing kinematic changes were smaller and shifted in opposite direction than corresponding measurements of the forewings. These findings suggest that intentional steering manoeuvres employ bulk shifts in depressor muscle timing that affect the timing of the stroke reversals thereby establishing asymmetric wing depression. Finally, we found indications that locusts may actively control the timing of forewing rotation and speculate this may be a mechanism for generating steering torques. These effects would act in concert with forces generated by asymmetric wing depression and angle of attack to establish rapid changes in direction.Abbreviations ASR acoustic startle response - dB SPL decibel sound pressure level (re: 20 Pa RMS) - EMG electromyogram - FWA forewing asymmetry - HWA hindwing asymmetry     

The control of wing kinematics by two steering muscles of the blowfly (Calliphora vicina)

We used a combination of high speed video and electrophysiological recordings to investigate the relationship between wing kinematics and the firing patterns of the first (b1) and second (b2) basalar muscles of tethered flying blowflies (Calliphora vicina). The b1 typically fires once during every wing stroke near the time of the dorsal stroke reversal. The b2 fires either intermittently or in bursts that may be elicited by a visual turning stimulus. Sustained activation of the b1 at rates near wing beat frequency appears necessary for the tonic maintenance of stroke amplitude. In addition, advances in the phase of b1 activation were correlated with both increased wing protraction during the down-stroke and increased stroke amplitude. Similar kinematic alterations were correlated with b2 spikes, and consequently, both muscles may function in the control of turns toward the contralateral side. The effects of the two muscles were evident within a single stroke period and decayed quickly. Kinematic changes correlated with b1 phase shifts were graded, suggesting a role in compensatory course stabilization. In contrast, b2 spikes were correlated with all-or-none changes in the wing stroke, a characteristic consistent with a role in mediating rapid turns towards or away from objects.Abbreviations b1 first basalar muscle - b2 second basalar muscle - PWP pleural wing process - RS radial stop - S wing span · - angle between the stroke plane and the longitudinal body axis - stroke amplitude - stroke elevation - L wing length - b1 phase of b1 activation - b2 phase of b2 activation - stroke deviation     

Activation phase ensures kinematic efficacy in flight-steering muscles of Drosophila melanogaster

During tethered flight in Drosophila melanogaster, spike activity of the second basalar flight-control muscle (M.b2) is correlated with an increase in both the ipsilateral wing beat amplitude and the ipsilateral flight force. The frequency of muscle spikes within a burst is about 100 Hz, or 1 spike for every two wing beat cycles. When M.b2 is active, its spikes tend to occur within a comparatively narrow phase band of the wing beat cycle. To understand the functional role of this phase-lock of firing in the control of flight forces, we stimulated M.b2 in selected phases of the wing beat cycle and recorded the effect on the ipsilateral wing beat amplitude. Varying the phase timing of the stimulus had a significant effect on the wing beat amplitude. A maximum increase of wing beat amplitude was obtained by stimulating M.b2 at the beginning of the upstroke or about 1 ms prior to the narrow phase band in which the muscle spikes typically occur during flight. Assuming a delay of 1 ms between the stimulation of the motor nerve and muscle activation, these results indicate that M.b2 is activated at an instant of the stroke cycle that produces the greatest effect on wing beat amplitude.     

The three-dimensional optomotor torque system ofDrosophila melanogaster

Summary The well known optomotor yaw torque response in flies is part of a 3-dimensional system. Optomotor responses around the longitudinal and transversal body axes (roll and pitch) with strinkingly similar properties to the optomotor yaw response are described here forDrosophila melanogaster. Stimulated by visual motion from a striped drum rotating around an axis aligned with the measuring axis, a fly responds with torque of the same polarity as that of the rotation of the pattern. In this stimulus situation the optomotor responses for yaw, pitch and roll torque have about the same amplitudes and dynamic properties (Fig. 2). Pronounced negative responses are measured with periodic gratings of low pattern wavelengths due to geometrical interference (Fig. 3). The responses depend upon the contrast frequency rather than the angular velocity of the pattern (Fig. 4). Like the optomotor yaw response, roll and pitch responses can be elicited by small field motion in most parts of the visual field; only for motion below and behind the fly roll and pitch responses have low sensitivity.The mutantoptomotor-blind ^H31 (omb ^H31) in which the giant neurones of the lobula plate are missing or severely reduced, is impaired in all 3 optomotor torque responses (Fig. 5) whereas other visual responses like the optomotor lift/thrust response and the landing response (elicited by horizontal front-to-back motion) are not affected (Heisenberg et al. 1978).We propose that the lobula plate giant neurons mediate optomotor torque responses and that the VS-cells in particular are involved in roll and pitch but not in lift/thrust control. This hypothesis accommodates various electrophysiological and anatomical observations about these neurons in large flies.Abbreviation EMD elementary movement detector     

Der Vorderflügel großer Heuschrecken als Luftkrafterzeuger

Summary The functional mechanics of the forewingtwisting ofLocusta migratoria L. is described and demonstrated by means of plastic models. The upstroke-supination (Z-profile) is produced by elastic and aerodynamic forces only. A tonic muscle, the muscle of the axillary 3, acts as upstroke-pronator, flattening the Z-profile. The three direct wing depressor muscles (basalar muscles, subalar muscle) pronate the wing during the downstroke. The basalar muscles initiate the wing-turning at the begin of downstroke by clicking the Z-profile into a reverse clap profile. The muscle of the axillary 3 decreases the downstroke-pronation, acting in this phase as a supinator. This muscle is therefore able to increase the aerodynamical angle of attack in both wingstroke phases. The functional significance of the muscles for the control of flight is discussed.     

Three‐dimensional geometry of a pterosaur wing skeleton,and its implications for aerial and terrestrial locomotion

This study reports on the three‐dimensional spatial arrangement and movements of the skeleton of Anhanguera santanae (Pterodactyloidea: Ornithocheiridae), determined using exceptionally well‐preserved uncrushed fossil material, and a rigid‐body method for analysing the joints of extinct animals. The geometric results of this analysis suggest that the ornithocheirids were inherently unstable in pitch and yaw. As a result, pitch control would probably have been brought about by direct adjustment of the angle of attack of the wing, by raising or lowering the trailing edge from the root using the legs if, as is indicated in soft‐tissue specimens of a number of unrelated pterosaur species, the legs were attached to the main wing membrane, or by using long‐axis rotations at the shoulder or wrist to raise and lower the trailing edge from the wingtip. An analysis of the three‐dimensional morphology of the wrist lends support to the idea that the pteroid – a long, slender wrist bone unique to pterosaurs that supported a membranous forewing – was directed forwards in flight, not towards the body. As a result, the forewing could have fulfilled the function of an air‐brake and high‐lift device, and may also have had an important role in pitch, yaw, and roll control. The joint analysis is consistent with a semi‐erect quadrupedal model of terrestrial locomotion in the ornithocheirids. © 2008 The Linnean Society of London, Zoological Journal of the Linnean Society, 2008, 154 , 27–69.     

On the sex-specific mechanisms of butterfly flight: flight performance relative to flight morphology, wing kinematics, and sex in Pararge aegeria

Many evolutionary ecological studies have documented sexual dimorphism in morphology or behaviour. However, to what extent a sex-specific morphology is used differently to realize a certain level of behavioural performance is only rarely tested. We experimentally quantified flight performance and wing kinematics (wing beat frequency and wing stroke amplitude) and flight morphology (thorax mass, body mass, forewing aspect ratio, and distance to centre of forewing area) in the butterfly Pararge aegeria (L.) using a tethered tarsal reflex induced flight set-up under laboratory conditions. On average, females showed higher flight performance than males, but frequency and amplitude did not differ. In both sexes, higher flight performance was partly determined by wing beat frequency but not by wing stroke amplitude. Dry body mass, thorax mass, and distance to centre of forewing area were negatively related to wing beat frequency. The relationship between aspect ratio and wing stroke amplitude was sex-specific: females with narrower wings produced higher amplitude whereas males show the opposite pattern. The results are discussed in relation to sexual differences in flight behaviour.  © 2006 The Linnean Society of London, Biological Journal of the Linnean Society , 2006, 89 , 675–687.     

Role of wing pronation in evasive steering of locusts

Evasive steering is crucial for flying in a crowded environment such as a locust swarm. We investigated how flying locusts alter wing-flapping symmetry in response to a looming object approaching from the side. Desert locusts (Schistocerca gregaria) were tethered to a rotatable shaft that allowed them to initiate a banked turn. A visual stimulus of an expending disk on one side of the locust was used to evoke steering while recording the change in wingbeat kinematics and electromyography (EMG) of metathoracic wing depressors. Locusts responded to the looming object by rolling to the contralateral direction. During turning, EMG of hindwing depressors showed an omission of one action potential in the subalar depressor (M129) of the hindwing inside the turn. This omission was associated with increased pronation of the same wing, reducing its angle-of-attack during the downstroke. The link between spike-omission in M129 and wing pronation was verified by stimulating the hindwing depressor muscles with an artificial motor pattern that included the misfire of M129. These results suggest that hindwing pronation is instrumental in rotating the body to the side opposite of the approaching threat. Turning away from the threat would be highly adaptive for collision avoidance when flying in dense swarms.     

Optomotor control of wing beat and body posture in drosophila

Continuous movement of striped patterns was presented on either side of a tethered fruitfly, Drosophila melanogaster, in order to simulate the displacement of stationary landmarks within the visual field of the freely moving fly. The horizontal components of the stimulus elicit, predominantly, yaw-torque responses during flight, or turning responses on the ground, which counteract involuntary deviations from a streight course in the corresponding mode of locomotion. The vertical components elicit, predominantly, covariant responses of lift and thrust which enable the fly to maintain a given level of flight. Monocular stimulation is sufficient to produce antagonistic responses, if the direction of the stimulus is reversed. The following constituents of the responses were derived mainly from properties of wing beat and body posture on photographs of fixed flight under visual stimulation. Wing stroke modulation (W. S. M.): The difference, and the sum, of the stroke amplitudes on either side are independently controlled by horizontal and vertical movement components, respectively. The maximum range of modulation per wing (12.3°) is equivalent to a 63% change in thrust on the corresponding side. Leg stroke modulation (L.S.M.): In the walking fly each pair of legs is under control of visual stimulation. The details of leg articulation are still unknown. Abdominal deflection (A.D.): An actively induced posture effect. Facilitates steering during free flight at increased air speed. Hind leg deflection (H.L.D.): Same as before. On most of the photographs the hind legs were deflected simultaneously and in the same direction as the abdomen. Hitch inhibition (H.I.): The term hitch denotes a transient reduction of stroke amplitude which seems to occur spontaneously and independently on either side of the fly. The hitch angle (12.2±3.8° S.D.) is most probably invariant to visual stimulation. Hitches are comparatively frequent in the absence of pattern movement. Their inhibition under visual stimulation is equivalent to an increase of the average thrust of the corresponding wing. The different constituents contribute to the optomotor responses according to the following tentative scheme (Fig. 7). The torque response is essentially due to the effects of W.S.M., A.D., H.L.D. and H.I., and the turning response to L.S.M. and possibly H.L.D., if the landmarks drift from anterior to posterior. So far, H.I. seems to be the only source of the torque response, and L.S.M. the only source of the turning response, if the landmarks drift in the opposite direction. The lift/thrust response results essentially from the effects of W.S.M. and H.I., no matter whether the landmarks drift from inferior to superior or in the opposite direction. The results obtained so far suggest that the optomotor control of course and altitude in Drosophila requires at least eight independent input channels or equivalent means for the separation of the descending signals from the visual centres. Further extension and refinement of the wiring scheme is required in order to improve the identification of the sensory inputs of the motor system and the classification of optomotor defective mutants.     

An analysis of bailer movements responsible for gill ventilation in the crab,cancer novae‐zelandiae

The movements of the bailer during normal ventilation can be resolved into two components, a cycle of pronation and supination being superimposed on a cycle of protraction and retraction. Pronation leads protraction with a phase angle of about 90° in a normal cycle. Pronation is accompanied by flexion of the bailer.

The skeletal anatomy of the bailer is such as to restrict movements of the bailer to those described above. Further the pronated and supinated positions of the limb represent the two stable positions of a skeletal click mechanism, the operation of which may help to resolve the functional duality of the promotor and remotor muscles.

This functional duality arises because the muscles are positioned so as to produce either protraction or supination of the limb. Other muscles in the limb are monofunctional. The bulk of muscle tissue responsible for protraction and supination seems to be greater than that responsible for pronation and retraction.

The sequence of muscular activity during the ventilation cycle follows that expected for a sequence, of protraction, supination, retraction and pronation. Overlap in the periods of activity of the bifunctional muscles and muscles responsible for pronation may also help to resolve the functional duality of the former.

The amplitude of bailer excursion (protraction‐retraction) is not greatly affected by changes in frequency. An advance in the onset of activity in some muscles at higher ventilation ? frequencies suggests that the system is tailored to produce a constant beat amplitude at all frequencies.

Pauses in ventilation occur with the bailer in the retracted position, and it is maintained in this position by tonic activity in the appropriate muscle. During normal ventilation the relative contraction duration of this muscle is positively correlated with cycle period, so that pauses apparently represent a prolongation of the normal retracted phase. The relative contraction durations of some other muscles are negatively correlated with cycle period. The different signs of these correlations may be related to the type of endogenous oscillator present in the central nervous system.     

Upper-limb surface electro-myography at maximum supination and pronation torques: the effect of elbow and forearm angle.

Forearm pronation and supination, and increased muscular activity in the wrist extensors have been both linked separately to work-related injuries of the upper limb, especially humeral epicondylitis. However, there is a lack of information on forearm torque strength at ranges of elbow and forearm angles typical of industrial tasks. There is a need for strength data on forearm torques at different upper limb angles to be investigated. Such a study should also include the measurement of muscular activity for the prime torque muscles and also other muscles at possible risk of injury due to high exertion levels during tasks requiring forearm torques.Twenty-four male subjects participated in the study that involved maximum forearm torque exertions for the right arm, in the pronation and supination directions, and at four elbow and three forearm rotation angles. Surface EMG (SEMG) was used to evaluate the muscular activity of the pronator teres (PT), pronator quadratus (PQ), biceps brachi (BB), brachioradialis (BR), mid deltoid (DT) and the extensor carpi radialis brevis (ECRB) during maximum torque exertions. Repeated measures ANOVA indicated that both direction and forearm angle had a significant effect on the maximum torques (p<0.05) while elbow angle and the interactions were highly significant (p<0.001). The results revealed that supination torques were stronger overall with a mean maximum value of 16.2 Nm recorded for the forearm 75% prone. Mean maximum pronation torque was recorded as 13.1 Nm for a neutral forearm with the elbow flexed at 45 degrees. The data also indicated that forearm angle had a greater effect on supination torque than pronation torque. Supination torques were stronger for the mid-range of elbow flexion, but pronation torques increased with increasing elbow extension. The strength profiles for the maximum torque exertions were reflected in the EMG changes in the prime supinators and pronators. In addition, the EMG data expressed as the percentage of Maximum Voluntary Electrical activity (MVE), revealed high muscular activity in the ECRB for both supination (26-43% MVE) and pronation torques (17-55% MVE). The results suggest that the ECRB acts as a stabiliser to the forearm flexors for gripping during pronation torques depending on forearm angle, but acts as a prime mover in wrist extension for supination torques with little effect of elbow and forearm angle. This indicates a direct link between forearm rotations against resistance and high muscular activity in the wrist extensors, thereby increasing stress on the forearm musculo-skeletal system, especially the lateral epicondyle.     

The role of delayed excitation in the co-ordination of some metathoracic flight motoneurons of a locust

Summary Intracellular recordings have been made from the somata of two metathoracic flight motoneurons, one innervating an elevator muscle of the hindwing, the tergosternal muscle 113 and the other a depressor, the first basalar muscle 127. The locust,Ghortoicetes terminifera was mounted ventral side uppermost with the thorax restrained and opened for access to the thoracic ganglia. Patterns of electrical activity recorded from the thoracic muscles were similar to those shown by a locust during flight when tethered in a more normal posture. In flight the left and right 113 motoneurons each receive a single impulse together at every stroke of the wing, with the 127 muscles active in approximate antiphase. A spike in a 113 motoneuron causes a delayed wave of excitation simultaneously upon itself and its contralateral partner (Fig. 2). The epsp's which form these waves summate and may cause a spike which follows the original one with a delay equal to the wingbeat period. The delayed excitation of the contralateral motoneuron is of larger amplitude than the ipsilateral one so that spikes in either motoneuron must activate separate but symmetrical pathways. A single spike may cause multiple waves in either motoneuron, each separated by intervals equal to the wingbeat period (Fig. 3). In the pathway must be neurons capable of reverberation.A spike in a 113 motoneuron causes a delayed excitation of the ipsilateral 127 motoneuron so that its membrane potential is lowered antiphasically to that of 113 (Fig. 17). A spike in a 127 motoneuron has no effect on the 113 motoneurons. In flight these pathways causing delayed excitation may co-ordinate the motoneurons.The left and right 113 motoneurons receive common synaptic inputs from at least two sources (Fig. 8). These occur as bursts of epsp's at intervals approximately equal to or multiples of the wingbeat period and in the absence of flight. Epsp's of sufficient amplitude cause a spike in the motoneuron which is in the correct phase in the flight pattern relative to any other active motoneurons (Fig. 9). During sustained flight epsp's contribute to the wave of depolarization that the motoneuron undergoes at each wingbeat (Fig. 11). In the absence of the epsp's the motoneuron does not oscillate on its own. At the end of flight bursts of epsp's may continue at the flight frequency long after all activity in the muscles has ceased.Beit Memorial Research Fellow.     

Der Vorderflügel großer Heuschrecken als Luftkrafterzeuger

Summary The mode is demonstrated in which the three regions of the forewings of large grasshoppers, i.e. the costal, radial and anal parts (Fig. 2) are folded against each other during up- and downstroke (Fig. 1; measurements made by W. Zarnack). The aerodynamic effects of this wing folding are determined from the measurements of lift carried out on wing models in parallel air stream (Fig. 3) and on rotating wing models (Fig. 4). Accordingly wing bending during downstroke generates distinctly higher lift at small and medium angles of attack than a flat wing having the same dimensions and moving at the same speed. It generates less lift at high angles of attack. Wing bending during upstroke generates higher lift only at>15°. Lift remains greater than that of a flat wing up to the highest angles of attack. These conclusions are supported by measurements of downstroke wind velocity (Fig. 5). Therefore it is possible to change the lift of right and left wings in order to generate moments for flight control around all three axes of the animal's system of co-ordinates without changing the rough kinematics of the beating wings.

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Der Verfasser dankt Dr. H.K. Pfau für die Einstellung der Flügelmodelle auf typische Mittelpositionen nach funktionsmorphologischen Gesichtspunkten (Abb. 2a) und Dr. W. Zarnack für die Vorpublikationserlaubnis der in Abb. 1 zusammengefaßten Meßdaten. Für meßtechnische Mitarbeit dankt er Frl. cand. rer. nat. U. Britz.     

Gleitflug des FlugbeutlersPetaurus breviceps papuanus (Thomas)

Summary Experiments with models made on thin flat plates were made in front of a wind tunnel in order to determine the relationship between their coefficients of lift and drag (Fig. 2) and the angle of attack as well as their aspects of flow (Fig. 8). The following results were achieved. When the plates were covered on one side with the fur from aPetaurus' flight skin, coefficients of lift at average angles of attack were improved, the critical angle of attack was increased and the characteristics of flow separation were flattened. However, these positive effects were only achieved by physiological orientation of the fur (i.e. placed on the upper surface with fur lying backwards; Fig. 3). The gliding number is improved at very high angles of attack only (Fig. 6). Thus the fur of aPetaurus acts as a lift generator within high (critical) angles of attack, during gliding flight (Nachtigall, 1979). Other natural and synthetic furs show a qualitatively similar, but quantitatively less distinct effect (Fig. 7). The aerodynamic efficiency of a fur coating is due to the boundary layer effects provided by the individual hairs which seem to act as miniature back-flow breaks (Fig. 8,9). The bionic transferability of this effect to technical wings is discussed.

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Mit Unterstützung der Deutschen Forschungsgemeinschaft

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Für melßtechnische Mitarbeit danke ich Frfiulein Hedwig Reichel und Herrn Rainer Grosch. Frau Lore Dinnendahl danke ich für Literaturhinweise.     

The relationship between eyespot shape and wing shape in the butterfly Bicyclus anynana: A genetic and morphometrical approach

The African butterfly, Bicyclus anynana, normally possesses circular eyespots on its wings. Artificial selection lines, which express ellipsoidal eyespots on the dorsal surface of the forewing, were used to investigate correlated changes in wing shape. Morphometric analysis of linear wing measurements and wing scale counts provided evidence that eyespot shape was correlated with localised shape changes in the corresponding wing-cell, with overall shape changes in the wing, and with the density/arrangement of scales around the eyespot area.