Flying Slower: Floor Pattern Object Size Affects Orthokinetic Responses During Moth Flight to Sex Pheromone

Previous studies with Oriental Fruit Moth (OFM, Grapholita molesta) and Heliothis virescens males flying upwind along a pheromone plume showed that they increased their upwind flight speed as they flew higher above striped floor patterns and, for OFM, to a similar degree over dotted floor patterns. This response pattern has been demonstrated in another moth species, Epiphyas postvittana and in a beetle, Prostephanus truncatus. In all cases the role played by the change in angular size of the wind tunnel’s ventral floor pattern was not assessed. In the present study we specifically addressed this question with a systematic examination of moths’ flight control over different sizes of transverse stripes and dot patterns ranging down by halves from 5 to 0.625 cm and a blank white floor as a control, and showed that OFM males fly faster upwind and along their flight paths over floor patterns of decreasing size. Increased speeds over striped patterns were evident as stripe width decreased below 2.5 cm, whereas moths did not increase their flight speed over dot patterns until dot size had decreased to less than 1.25 cm. Another flight component that the moths can actively control, their course angles, was unchanged above both patterns, except for moths flying over 5 cm stripes. Turning frequency and interturn distances were mostly unchanged or offset each other, negating any effects on upwind progress. As in an earlier study examining flight speeds at three heights above floor patterns of three densities, the moths’ changes in speed appear to be exclusively affected by changes in their orthokinetic response to the size of the floor pattern objects.     

粘虫飞行对生殖及寿命的影响

该文报道了粘虫Mythimna separata（Walker）成虫飞行后产卵、交配及寿命的研究结果。1日龄成虫飞行6 h、12 h、18 h、24 h后的产卵前期均显著短于对照的,其中飞行6 h、12 h的比对照的短2天以上,产卵量均比对照的高。对1～5日龄成虫分别飞行23.5 h后的研究结果表明,1日龄飞行的产卵前期和上述结果相一致。2～4日龄飞行的与对照的没有显著差异,但产卵量则随飞行日龄的延迟而逐渐减少。5日龄飞行的产卵前期显著延长,产卵量已不到对照的一半。所有经过飞行的成虫产卵高峰日比对照的早1天。不同日龄成虫飞行时间、距离与成虫产卵量的关系为：1～3日龄飞行时间、距离长的个体产卵量也高;但4～5日龄的成虫飞行时间与距离越长,其产卵量越少,表现出明显的卵子发生飞行拮抗症(oogenesis-flight syndrome)。除了5日龄飞行的成虫交配率有所下降以外,所有经过飞行的成虫产卵历期、交配率及寿命与对照的没有显著差异。最后,根据这些结果,对粘虫迁飞的起飞时期,迁飞在粘虫生殖、种群动态及成灾规律中的作用进行了讨论。     

温度对甜菜夜蛾飞行能力的影响

温度对甜菜夜蛾飞行能力有显著的影响（P<0.05）。在16～32℃内,成虫均能进行正常的飞行活动。24℃下的成虫飞行能力最强,在15 h的吊飞飞行中,成虫飞行距离最远（37.14 km）、飞行速度最快（0.87 m/s）、飞行时间最长（11.73 h）。温度低于２０℃或高于２８℃时,其飞行能力均显著降低。甜菜夜蛾在不同温度下飞行时对主要能源物质（甘油三酯）的利用效率不同。在较适宜的温度下,尽管成虫飞行消耗的甘油三酯较多,但单位飞行距离所消耗的甘油三酯却较少,即利用效率较高,表明成虫飞行能源物质利用效率的不同是导致其在不同温度下飞行能力产生差异的主要原因之一。     

REGULATION OF FLIGHT CAPACITY AND CONTENTS OF ENERGY SUBSTANCES BY METHOPRENE IN THE MOTHS OF ORIENTAL ARMYWORM,MYTHIMNA SEPARATA*

Abstract The flight capacity and contents of energy substances in the moths of migratory Oriental armyworm, Mythimna separata (Walker)dosed with juvenile hormone analogue methoprene(JHM) were compared with the normal moth through day‐1 to day‐6 after the treatment. The flight capacity of JHM‐treated moths, as determined by a 12‐hours tethered‐flight test, was significantly lower than that of the controls, although it might differ with their age and sex. The moth's flight capacity between the treatments was insignificantly different from the first to 3rd day after the treatment but was significantly different from the 4th to 6th day either in the mean flight duration or in distance. Evaluation of the long fliers at the same stages between the treatments also supported this finding. Flight capacity of the JHM‐treated moths also differed with the sex. The JHM‐treated female did not fly less than the control from day‐1 to day‐3, but did significantly less from day‐4 to day‐6 after the treatment. The flight capacity of the JHM‐treated males, however, was not weaker than that of the control throughout the test period. Comparison of the levels of energy substances in the JHM‐treated adults and the controls showed that JHM may directly acted on metabolism of glyceride, which in turn affected flight capacity. Furthermore, higher levels of glyceride in the treated male adults raised their flight capacity to a stronger levels than the control in most of the days of tethered‐flight test period. Contents of glycogen, however, were insignificantly affected by JHM in both male and female adults. In might therefore be concluded that levels of JH is a critical factor regulationg migratory behavior in the army worm moth. In addition to affect metabolism of glyceride, other possible physiological roles that JH played in determining migrattory behavior are also discussed.     

Auditory-evoked evasive manoeuvres in free-flying locusts and moths

We presented free-flying locusts (Locusta migratoria L.) with sounds that varied in temporal structure and carrier frequency as they flew toward a light source in a flight room under controlled temperature and light conditions. Previous studies have shown tethered locusts react more often to trains of 30-kHz pulses than to pulse trains below 10 kHz. Further, this acoustic startle response has been suggested to function in bat-avoidance. We expected free-flying locusts to respond similarly; however, we found locusts responded to all sounds we presented, not just high-frequency, bat-like sounds. Response rates of turns, loops, and dives varied from 6% to 26% but were statistically independent of carrier frequency and/or pulse structure. Free-flying moths and tethered locusts were tested using a subset of our acoustic stimuli under the same temperature and light conditions as the free-flying locusts. Moth responses were carrier frequency dependent as were responses of tethered locusts positioned along the flight path observed in our free-flight trials. All responses were unaffected by a 90% reduction in room light. We conclude that locusts possess an acoustic startle response evocable in free flight, however, free-flying locusts do not show the same discrimination observed in tethered locusts under similar conditions.Abbreviations ASR acoustic startle response - dB SPL decibel sound pressure level (RMS re: 20 Pa)     

Reduced antennal sensitivity, behavioural response, and attraction of male codling moths, Cydia pomonella, to their pheromone (E,E)-8,10-dodecadien-1-ol following various pre-exposure regimes

The effects of pre‐exposing male codling moths, Cydia pomonella (L.) (Lepidoptera: Tortricidae), to their pheromone (E,E)‐8,10‐dodecadien‐1‐ol (codlemone), in static and moving air, under laboratory and field conditions, on subsequent antennal sensitivity, behavioural responsiveness, and attraction to codlemone were investigated. In flight tunnel experiments, the percentage of moths wing fanning and taking flight were mostly unaffected, but upwind flight to, and contact with, pheromone sources known to elicit responses of both were shown to depend on the intensity and duration of previous exposure to codlemone and recovery time between exposure and assessment. Ten to 30‐min pre‐exposures to codlemone in static air (≈ 35 µg l^?1) not only caused a 99% reduction in attraction, but also significantly reduced electroantennogram response to codlemone. Recovery of full antennal sensitivity to codlemone took more than 1 h, but recovery of attraction took over 4 h, suggesting that habituation is also partially involved in reduced behavioural responsiveness following pre‐exposure. Seventy‐five min exposures to codlemone in moving air (5–10 cm s^?1) at rates of 0.9, 4.5, and 18 µg h^?1 from Celcon fibres caused 75, 86, and 99% disruption, respectively. However, 30–34‐h exposure of caged moths to air moving through an orchard treated with 1000 Isomate‐C® dispensers ha^?1 releasing approximately 20 µg h^?1 per dispenser during tests, had no impact on moth response in flight‐tunnel assays 30 min after removal from the orchard. In this treated orchard, catches of free‐flying moths in pheromone‐baited traps were completely inhibited. If observed mechanisms such as long‐lasting antennal adaptation or habituation of the central nervous system contribute to the disruption of pheromone communication among codling moths under field conditions, it seems unlikely that they occur following exposure to the average atmospheric concentrations of codlemone. For these effects to be important, codling moths may require close contact with pheromone sources for extended periods, or repeated close encounters.     

Observations of the flight behaviour of the army worm moth, Spodoptera exempta, at an emergence site using radar and infra-red optical techniques

ABSTRACT.

• 1 Studies were made in Kenya of the flight behaviour of African armyworm moths which had emerged from areas previously infested with‘gregarious’caterpillars. The use of radar and an infra-red optical detector permitted quantitative, direct observations of the flying moths, over all of their flight altitudes, without disturbing their behaviour.
• 2 Almost all of the successfully emergent moths climbed to altitudes of several hundred metres above ground level and migrated from the emergence sites. Their migratory flights sometimes started on the night of emergence, but on other occasions the moths remained roosting in trees until dawn, then engaged in short dispersal flights, concealed themselves during the day. and commenced migration in mass flights at dusk the following night.
• 3 The onset of these‘dusk flights’occurred when the irradiance level fell on average to 2.7 × 10^?5Wm^?2 nm^?1 in the 450–800 nm range (in the photometric units appropriate for human vision this corresponds approximately to 2 lux). The‘dawn flights’began with the first sustained increase in irradiance at dawn, and terminated at the end of dawn twilight.
• 4 Migratory flight in the strong, easterly winds which usually occurred during the first half of the night resulted in rapid, down-wind displacement to the west. Observations of groups of flying moths passing successively over two radars demonstrated that these migrations could cover at least 20 km.
• 5 In the second half of the night, winds were usually weak and variable, and up-wind or cross-wind directions of displacement were sometimes observed.
• 6 Moths were observed to disperse rapidly during their migration, so that the mass influxes which lead to outbreaks must be a consequence of subsequent reconcentration. The importance of meso-scale wind convergence zones in reconcentrating flying moths, and the role of rainfall in inducing descent, and possibly landing, are discussed.

     

The behaviour of flying green lacewings, Chrysopa carnea, in the presence of ultrasound

Green lacewings stop flying in response to ultrasound. The behavioural response begins with folding of the wings, which starts about 40 msec following stimulation. About 66 msec later potentials from the indirect flight muscles cease. Insects resume their stationary flight after a certain period of time, which is dependent on the stimulus duration. Consistent responses occur only during the insects' night. Stimuli eliciting the cessation of flight have the following parameters: frequencies of from 15 to 140 kHz, intensities above 55 dB, single pulses of from 1 to 100 msec in duration, and pulse sequences having repetition rates up to 70 or 80 pulses/sec. Pulse sequences from 0·1 to 1 sec produce response durations that last longer than the stimulus, whereas pulse sequences longer than 1 sec, elicit responses that do not last as long as the stimulus. The duration of the response remains nearly constant when single ultrasonic pulses are given. This flight cessation behaviour provides a mechanism whereby green lacewings can avoid predation by bats. Responses seen in green lacewings are compared with similar responses in noctuid moths.     

Longevity,flight ability and reproductive performance of the diamondback moth,Plutella xylostella (L.) (Lepidoptera: Yponomeutidae), related to adult body size

Plutella xylostella in the temperate zone shows a clear seasonal change in adult body size. In the laboratory, large and small moths were produced during immature stages at 15°C and 25°C, respectively. These moths were then used to evaluate longevity, age-specific flight ability, flight ability of mated and unmated females, and the influence of flight experience on the subsequent reproductive success. The large moths lived longer and displayed a greater flight ability over 3 weeks. Irrespective of body size, unmated females flew for a longer time than mated females, and flight experience affected their subsequent reproductive success. Females of both sizes mated and laid eggs soon after emergence, without any obvious pre-reproductive period. More flight experience did not delay oviposition, but did reduce egg production. It is likely that large moths with a longer adult life span and greater flight ability are better fitted for long-distance flight and more fecund than small ones. These experimental results may explain why long-distance migration ofP. xylostella is mostly seen during cool seasons, when relatively large moths with long forewing appear in the field.     

Prey pursuit strategy of Japanese horseshoe bats during an in-flight target-selection task

The prey pursuit behavior of Japanese horseshoe bats (Rhinolophus ferrumequinum nippon) was investigated by tasking bats during flight with choosing between two tethered fluttering moths. Echolocation pulses were recorded using a telemetry microphone mounted on the bat combined with a 17-channel horizontal microphone array to measure pulse directions. Flight paths of the bat and moths were monitored using two high-speed video cameras. Acoustical measurements of returning echoes from fluttering moths were first collected using an ultrasonic loudspeaker, turning the head direction of the moth relative to the loudspeaker from 0° (front) to 180° (back) in the horizontal plane. The amount of acoustical glints caused by moth fluttering varied with the sound direction, reaching a maximum at 70°–100° in the horizontal plane. In the flight experiment, moths chosen by the bat fluttered within or moved across these angles relative to the bat’s pulse direction, which would cause maximum dynamic changes in the frequency and amplitude of acoustical glints during flight. These results suggest that echoes with acoustical glints containing the strongest frequency and amplitude modulations appear to attract bats for prey selection.     

Visual ground pattern modulates flight speed of male Oriental fruit moth Grapholita molesta

Insects flying in a horizontal pheromone plume must attend to visual cues to ensure that they make upwind progress. Moreover, it is suggested that flying insects will also modulate their flight speed to maintain a constant retinal angular velocity of terrestrial contrast elements. Evidence from flies and honeybees supports such a hypothesis, although tests with male moths and beetles flying in pheromone plumes are not conclusive. These insects typically fly faster at higher elevations above a high‐contrast ground pattern, as predicted by the hypothesis, although the increase in speed is not sufficient to demonstrate quantitatively that they maintain constant visual angular velocity of the ground pattern. To test this hypothesis more rigorously, the flight speed of male oriental fruit moths (OFM) Grapholita molesta Busck (Lepidoptera: Tortricidae) flying in a sex pheromone plume in a laboratory wind tunnel is measured at various heights (5–40 cm) above patterns of different spatial wavelength (1.8–90°) in the direction of flight. The OFM modulate their flight speed three‐fold over different patterns. They fly fastest when there is no pattern in the tunnel or the contrast elements are too narrow to resolve. When the spatial wavelength of the pattern is sufficiently wide to resolve, moths fly at a speed that tends to maintain a visual contrast frequency of 3.5 ± 3.2 Hz rather than a constant angular velocity, which varies from 57 to 611° s^?1. In addition, for the first time, it is also demonstrated that the width of a contrast pattern perpendicular to the flight direction modulates flight speed.     

Influence of Nematode Parasitism,Body Size,Temperature, and Diel Period on the Flight Capacity of <Emphasis Type="Italic">Sirex noctilio</Emphasis> F. (Hymenoptera: Siricidae)

Sirex noctilio F. (Hymenoptera: Siricidae) is a woodwasp of pine trees that has recently invaded and established in North American forests. Although S. noctilio has had a limited impact in North America to date, there is some concern that it could have a significant impact on pine plantations, especially in the southeastern U.S.A. Moreover, there are few data on the flight capacity of male S. noctilio. We found no association between parasitism by D. siricidicola and whether or not S. noctilio initiated flight on the flight mill. Male wasps that were parasitized by nematodes were heavier than non-parasitized males, but there was no significant difference in mass between parasitized and non-parasitized females. We also examined the flight capacity of male and female S. noctilio in relation to nematode parasitism, body mass, temperature (for only males), and diel period. Body mass, temperature, and diel period affected flight in S. noctilio such that wasps were generally observed to fly faster, farther, and more frequently if they were heavier, flying at warmer temperatures, and flying during the photoperiod. The fact that nematode-parasitized male wasps were found to fly farther than the non-parasitized males is consistent with the hypothesis that nematode parasitism does not negatively affect the flight capacity of S. noctilio.     

Fast and slow flight torque responses in flies and their possible role in visual orientation behaviour

The flight torque responses of tethered flying houseflies to motion and presentation or removal of a vertical dark stripe on a bright background were recorded in real time. Motion with constant speed of 100° s^-1 from front to back elicits a strong fast response following the diraction of the stimulus motion. Motion from back to front elicits a weaker response. Instantaneous presentation and removal of a stationary stripe elicit weak, slow response. Apparent motion from front to back and from back to front elicit weak responses with a fast, directionally selective, transient peak followed by a slow response component oriented towards the stripes position. The fast transient peak response is not elicited if the animals were stimulated before with real movement of the stripe. The results are discussed and an earlier proposed model for free flight tracking and fixation is extended.     

Flying Faster: Flight Height Affects Orthokinetic Responses During Moth Flight to Sex Pheromone

Male Oriental Fruit Moths (Grapholita molesta) flew faster toward a pheromone source as they flew higher above striped and dotted floor patterns. The moths significantly (P?<?0.05) increased their ground speed over floor patterns of transverse stripes or pseudo randomly placed dots. The moths’ track angles (flight path angle off the windline) decreased significantly (P?<?0.05) when they flew 40 cm above the floor patterns vs. flight at 10 cm up, and they tended to steer more upwind flight (smaller course angles) at the upper, 40 cm, height compared to 10 cm up. Turn frequencies and reversal distances across the wind line were also affected by dot density. However, the interaction of small changes in flight speed, course angle, turn widths and turn frequencies are difficult to assess; I have subsumed all their affects into a simple measure of “total distance” flown by the moths by summing the length of all flight vectors analyzed for the other metrics, but no differences were found. By far, the largest change in flight was the positive orthokinetic response to increased flight height above both striped and dotted floor patterns (Fig. 2; P?<?0.05), and nearly all other changes appear to be entirely due to faster moth flight with little or no changes in steering or turning patterns.     

The dawn flight of the gold swift Hepialus hecta: predator avoidance and the integration of complex lek behaviour (Lepidoptera,Hepialidae)

Predator pressure is a considerable evolutionary force. The evening twilight flight of species in the family Hepialidae Swift moths has been attributed to the moths (which have no hearing and so cannot detect bats) flying in a bat/bird free window. Several species deploy elaborate lek behaviour in this period. The expected flight in the dawn twilight is little reported, except in the non‐leking Hepialus (Korscheltellus) gracilis. A detailed study of the dawn flight in the leking species Hepialus (Phymatopus) hecta shows that it is less extensive than the evening lek flight (both in duration and in the number of moths participating), is confined to a much narrower window around sunrise, involves no reproductive behaviour, and functions only to re‐locate the members of copulating pairs and sessile displaying males from the emergent ground vegetation to less conspicuous roosting sites. Compilation of individual biographies over the 24‐h cycle permits a full construction of the diel activity in time and space. It consists of two twilight flight periods, separated by prolonged roosting during the hours of darkness and daylight. The moths use almost the whole available range of roosting sites, from the base of the ground vegetation to the tree canopy, and cyclically leave and re‐enter the lek site from these positions. The copulating posture and position avoid mammalian predators, and facilitate escape from spiders and wasps by the efficient use of a dead drop. The narrowness of the dawn flight is attributed to the need for this prolonged but conspicuous copulation, which precludes a morning mating, and to a demonstrated asymmetry of twilight activity in birds. The whole integrated spatio‐temporal cycle is attributable to evolutionary pressure to minimize the impact of predators, demonstrated to include birds, bats, wasps, and spiders, and probably also dragonflies, mice and shrews; the pre‐existing dawn flight is permissive to the evolution of sessile male displays during the evening lek. © 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2013, 110 , 305–319.     

Time-correlated flights of juvenile and mature locusts: A comparison between free and tethered animals

The flights of free and tethered Locusta migratoria were followed from initiation with a high-speed film camera. A longer sequence of wing-beat cycles can thus be correlated unequivocally with the animals's movement in time and space. In both flight situations the locusts start with approximately the same instantaneous wing-beat frequency. During the early flight phase free-flying animals increase their wing-beat frequency, whereas for tethered locusts this parameter remains constant or even decreases. The general flight pattern is similar in juvenile and mature locusts; the juveniles however, fly with alower wing-beat frequency and flight speed. The differences in the wing-beat frequencies for both flight performances are discussed with respect to differences in the sensory inputs to the flight motor centre.     

Dual Dimensionality Reduction Reveals Independent Encoding of Motor Features in a Muscle Synergy for Insect Flight Control

What are the features of movement encoded by changing motor commands? Do motor commands encode movement independently or can they be represented in a reduced set of signals (i.e. synergies)? Motor encoding poses a computational and practical challenge because many muscles typically drive movement, and simultaneous electrophysiology recordings of all motor commands are typically not available. Moreover, during a single locomotor period (a stride or wingstroke) the variation in movement may have high dimensionality, even if only a few discrete signals activate the muscles. Here, we apply the method of partial least squares (PLS) to extract the encoded features of movement based on the cross-covariance of motor signals and movement. PLS simultaneously decomposes both datasets and identifies only the variation in movement that relates to the specific muscles of interest. We use this approach to explore how the main downstroke flight muscles of an insect, the hawkmoth Manduca sexta, encode torque during yaw turns. We simultaneously record muscle activity and turning torque in tethered flying moths experiencing wide-field visual stimuli. We ask whether this pair of muscles acts as a muscle synergy (a single linear combination of activity) consistent with their hypothesized function of producing a left-right power differential. Alternatively, each muscle might individually encode variation in movement. We show that PLS feature analysis produces an efficient reduction of dimensionality in torque variation within a wingstroke. At first, the two muscles appear to behave as a synergy when we consider only their wingstroke-averaged torque. However, when we consider the PLS features, the muscles reveal independent encoding of torque. Using these features we can predictably reconstruct the variation in torque corresponding to changes in muscle activation. PLS-based feature analysis provides a general two-sided dimensionality reduction that reveals encoding in high dimensional sensory or motor transformations.     

Tethered flight of the potato moth, Phthorimaea operculella

ABSTRACT. The effects of sex, age and mated state on average flight speed, duration and distance were determined for potato moths, Phthorimaea operculella (Zeller) (Lepidoptera, Gelechiidae), tethered to flight mills. Moths were classified as non-fliers (NFs), good-fliers (GFs) and remaining-fliers (RFs) on the basis of their performance over the first two flights. Some moths flew for over 5 h non-stop, while others tethered overnight flew between 20 and 30 km. Speed, duration and distance flown were greater during the first flight. First flight duration and distance flown by females decreased with age, whereas no trend was evident for males. Mated males and females flew slower first flights with increasing age, whereas virgin moths showed no marked trend. The analysis of fliers and NFs revealed that GFs were heavier than both RFs and NFs, GFs were faster than RFs, the percentage of NFs increased with age especially for mated females, and the percentage of GFs decreased with age. Age and mated state are important factors influencing flight performance especially for female moths. The relevance of these results to the field situation and the possible application of tethered flight to tests of potato moth quality are discussed.     

Visuomotor Response to Object Expansion in Free-Flying Bumble Bees

The flight control systems of flying insects enable many kinds of sophisticated maneuvers, including avoidance of midair collisions. Visuomotor response to an approaching object, received as image expansion on insects’ retina, is a complex event in a dynamic environment where both animals and objects are moving. There are intensive free flight studies on the landing response in which insects receive image expansion by their own movement. However, few studies have been conducted regarding how freely flying insects respond to approaching objects. Here, using common laboratory insects for behavioral research, the bumblebee Bombus ignitus, we examined their visual response to an approaching object in the free-flying condition. While the insect was slowly flying in a free-flight arena, an expanding stripe was projected laterally from one side of the arena with a high-speed digital mirror device projector. Rather than turning away reported before, the bumble bees performed complex flight maneuvers. We synchronized flight trajectories, orientations and wing stroke frequencies with projection parameters of temporal resolution in 0.5 ms, and analyzed the instantaneous relationship between visual input and behavioral output. In their complex behavioral responses, we identified the following two visuomotor behaviors: increasing stroke frequency when the bumble bees confront the stripe expansion, and turning towards (not away) the stripe expansion when it is located laterally to the bee. Our results suggested that the response to object expansion is not a simple and reflexive escape but includes object fixation, presumably for subsequent behavioral choice.     

粘虫迁飞模拟试验

粘虫是我国禾谷类作物的主要迁飞性害虫之一。近十多年来,我国昆虫学者在迁飞问题上作了大量研究工作。迄今已基本摸清了我国东部粘虫的远距离迁飞、迁飞方向及路线(林昌善等,1963;林昌善、张宗炳,1963),分析了粘虫迁飞的生理生态机制(马世骏,1963)和迁飞与气流场的关系(林昌善,19632 赵圣菊等,1981),开展了一些粘虫飞行的观察和