Migrations of dragonflies (Odonata) in the south of the West Siberian plain

The paper presents a summary of mass dragonfly migrations observed previously in Russia, in particular in West Siberia. From 1969 to 2009, the authors studied the dynamics of dragonfly population, their spatial distribution and movements in the West Siberian forest-steppe. The main studies were conducted in the Lake Chany basin (the Biological Station of the Institute of Animal Systematics and Ecology, Siberian Division, Russian Academy of Sciences). The spatial redistribution of dragonflies is regarded as a balance of homing and wandering behavior. Homing results in a relative stability of local dragonfly populations and assemblages, while wandering leads to dispersal of dragonflies from their emergence sites and colonization of new habitats; the latter is especially important due to the ephemeral nature of many shallow reservoirs where the nymphs develop. The formation of more or less constant migration routes is a peculiar variant of wandering activities. A special type of dragonfly migrations is mass exodus from native habitats, triggered by excessive population growth and leading to elimination of all or most individuals. Such migrations not only optimize the size of dragonfly populations but also facilitate removal of nutrients and organic matter from eutrophic water bodies. An original generalized classification of dragonfly migrations is proposed.     

Simultaneous monitoring of flight and oviposition of individual velvetbean caterpillar moths

ABSTRACT. A 'pivot' flight actograph was combined with a rolling oviposition surface to characterize the flight and oviposition behaviour of velvetbean caterpillar moths, Anticarsia gemmatalis Hubner. Tethered, caged control females laid significantly more eggs that those flown on the actograph. Mated females laid more eggs than unmated ones. However, mating did not affect longevity nor fight frequency and duration. Laboratory-reared and wild-type females also did not differ signficantly in longevity and flight. Both laboratory and wild mated females laid most of their eggs during the first 7 days whereas unmated ones delayed their oviposition. None of the female types produced a definite hourly, daily or lifetime pattern in flight frequency or duration. Of the 7672 recorded flights, about 3% were greater than 0.5 h. 'Long' flights (>0.5h) were made by some females before oviposition, as in colonization migration, but most interspersed flight with oviposition, as in extended search migration.     

Do container size and predator presence affect Culex (Diptera: Culicidae) oviposition preferences?

Organisms with complex life cycles typically do not exhibit parental care. Hence, the ability of adult females to choose quality oviposition sites is critical for offspring success. Gravid females of many insect taxa have the capability to detect environmental conditions in water-holding containers (e.g., resource level, presence of competitors or predators) and to choose the sites that are most suitable for offspring growth and development. Mosquitoes may also detect physical container characteristics related to water permanence such as surface area, volume, or container size, and some species such as those in the genus Culex have been shown to prefer larger containers. However, predators may also preferentially colonize larger containers; thus, ovipositing females may face decisions based on cues of site quality that balance the costs and benefits for offspring. We used a field experiment to evaluate the oviposition preferences of two Culex species in response to experimental container size and predator abundances within the containers. We found that both species avoided ovipositing in the largest containers, which have high abundances of Chaoborus sp. and dragonfly larvae (predators). However, the container size most commonly chosen for oviposition (15-L buckets) also had high mean abundance per liter of dragonfly larvae. These results suggest either prey naiveté or reduced vulnerability of these species to dragonflies compared to Chaoborus sp. Other potential mechanisms for the observed patterns are discussed.     

Prey detection of aquatic predators: Assessing the identity of chemical cues eliciting prey behavioral plasticity

Chemical cues transmitted through the environment are thought to underlie many prey responses to predation risk, but despite the known ecological and evolutionary significance of such cues, their basic composition are poorly understood. Using anuran tadpoles (prey) and dragonfly larvae (predators), we identified chemical cues associated with predation risk via solid phase extraction and mass spectrometry of the extracts. We found that dragonfly larvae predators consistently produced a negative ion, m/z 501.3, when they fed on bullfrog (Rana catesbeiana) and mink frog (Rana septentrionalis) tadpoles, but this ion was absent when dragonflies were fasted or fed invertebrate prey. When tadpole behavioral responses to dragonfly chemical cues were examined, tadpoles reduced their activity, particularly in response to dragonflies feeding on tadpoles. Furthermore, a negative correlation was noted between the level of tadpole activity and the concentration of the m/z 501.3 compound in dragonfly feeding trials, indicating that this ion was possibly responsible for tadpole anti-predator behavior.     

Peculiarities of structural-functional organization of the motor neuropil in the dragonfly thoracic ganglia

The study considers structural-functional relations in motor neuropil of the thoracic ganglia in dragonflies-insects capable of performing very complex and fast maneuvering in flight. The motor neuropil in dragonflies was shown to be more differentiated than in less mobile insects, while its motor nuclei are more outlined and approached to each other. There were revealed dendrites of the leg muscle motoneurons (intermediate nucleus), running to the anterior and posterior nuclei that contain dendrites of the wing muscle motoneurons. A possible role of such a dendrite approaching is discussed for close functional cooperation of wing and leg muscles essential for dragonflies to catch a large prey in flight by using their legs. Peculiarities of structural organization of the wing muscle motoneurons in dragonflies and locusts are considered to suggest the greater functional capabilities of motoneurons in the dragonfly motor apparatus.     

Prey pursuit and interception in dragonflies

Perching dragonflies (Libellulidae; Odonata) are sit-and-wait predators, which take off and pursue small flying insects. To investigate their prey pursuit strategy, we videotaped 36 prey-capture flights of male dragonflies, Erythemis simplicicollis and Leucorrhinia intacta, for frame-by-frame analysis. We found that dragonflies fly directly toward the point of prey interception by steering to minimize the movement of the prey's image on the retina. This behavior could be guided by target-selective descending interneurons which show directionally selective visual responses to small-object movement. We investigated how dragonflies discriminate distance of potential prey. We found a peak in angular velocity of the prey shortly before take-off which might cue the dragonfly to nearby flying targets. Parallax information from head movements was not required for successful prey pursuit. Accepted: 11 November 1999     

Interactive effects of body mass changes and species‐specific morphology on flight behavior of chick‐rearing Antarctic fulmarine petrels under diurnal wind patterns

For procellariiform seabirds, wind and morphology are crucial determinants of flight costs and flight speeds. During chick‐rearing, parental seabirds commute frequently to provision their chicks, and their body mass typically changes between outbound and return legs. In Antarctica, the characteristic diurnal katabatic winds, which blow stronger in the mornings, form a natural experimental setup to investigate flight behaviors of commuting seabirds in response to wind conditions. We GPS‐tracked three closely related species of sympatrically breeding Antarctic fulmarine petrels, which differ in wing loading and aspect ratio, and investigated their flight behavior in response to wind and changes in body mass. Such information is critical for understanding how species may respond to climate change. All three species reached higher ground speeds (i.e., the speed over ground) under stronger tailwinds, especially on return legs from foraging. Ground speeds decreased under stronger headwinds. Antarctic petrels (Thalassoica antarctica; intermediate body mass, highest wing loading, and aspect ratio) responded stronger to changes in wind speed and direction than cape petrels (Daption capense; lowest body mass, wing loading, and aspect ratio) or southern fulmars (Fulmarus glacialoides; highest body mass, intermediate wing loading, and aspect ratio). Birds did not adjust their flight direction in relation to wind direction nor the maximum distance from their nests when encountering headwinds on outbound commutes. However, birds appeared to adjust the timing of commutes to benefit from strong katabatic winds as tailwinds on outbound legs and avoid strong katabatic winds as headwinds on return legs. Despite these adaptations to the predictable diurnal wind conditions, birds frequently encountered unfavorably strong headwinds, possibly as a result of weather systems disrupting the katabatics. How the predicted decrease in Antarctic near‐coastal wind speeds over the remainder of the century will affect flight costs and breeding success and ultimately population trajectories remains to be seen.     

Conservation of a groundwater-dependent mire-dwelling dragonfly: implications of multiple threatening processes

Groundwater-dependent ecosystems and their dependent species are under increasing threat globally. Petalurid dragonflies are one such group. This review highlights processes that threaten the groundwater-dependent mire habitats of Petalura gigantea, a dragonfly with long-lived fossorial larvae. The species is reliant for successful reproduction on areas of emergent seepage, or at least, on a water table that is sufficiently high to cause saturation of the peaty substrate. These microhabitat characteristics are critical for successful oviposition and larval burrow establishment, making the species particularly vulnerable to any lowering of water tables. The effect of any lowering of water tables, due to groundwater abstraction or longwall coal mining, for example, will be compounded by the effects of more intense fire regimes in these mires and by projected climate change. These threatening processes act in conjunction with a range of other anthropogenic threats and are mirrored globally in threats to other groundwater-dependent mire ecosystems and their dependent species, including other petalurid dragonflies.     

Influence of adult experience on host microhabitat location by the generalist parasitoid,Campoletis sonorensis (Hymenoptera: Ichneumonidae)

The effect of adult experience on microhabitat location behavior of the generalist parasitoid Campoletis sonorensis (Cameron)was examined in a wind tunnel bioassay. Responses were tested to the odors of two host plants (cotton and sesame) of Heliothis virescens (F.) or a nonhost plant (potato), either damaged and infested with host larvae and host products (host/plant complex) or intact, clean and uninfested. Parasitoid females remained naive or were allowed one oviposition experience on either of the plants, 1 min, 2 h, or 24 h prior their introduction into the wind tunnel. In a no-choice test, parasitoids experienced 1 min prior to bioassay completed significantly more flights to sesame and potato host/plant complexes than did naive parasitoids. However, 24 h after experience, only females experienced on potato completed more flights to the host/ plant complex than did naive females. Parasitoids experienced 1 min prior to flight to undamaged plants showed a slight increase in flight response (significant only for potato) but, after 24 h, completed only as many flights as naive parasitoids. In a dual-choice situation, parasitoids did not show a preference for either of the two host plants but did prefer a host to a nonhost plant. This innate plant preference was not changed by a single oviposition experience. The potential significance of these results to the microhabitat location behavior of C. sonorensisin the field is discussed.     

Effects of an invasive plant transcend ecosystem boundaries through a dragonfly-mediated trophic pathway

Trophic interactions can strongly influence the structure and function of terrestrial and aquatic communities through top-down and bottom-up processes. Species with life stages in both terrestrial and aquatic systems may be particularly likely to link the effects of trophic interactions across ecosystem boundaries. Using experimental wetlands planted with purple loosestrife (Lythrum salicaria), we tested the degree to which the bottom-up effects of floral density of this invasive plant could trigger a chain of interactions, changing the behavior of terrestrial flying insect prey and predators and ultimately cascading through top-down interactions to alter lower trophic levels in the aquatic community. The results of our experiment support the linkage of terrestrial and aquatic food webs through this hypothesized pathway, with high loosestrife floral density treatments attracting high levels of visiting insect pollinators and predatory adult dragonflies. High floral densities were also associated with increased adult dragonfly oviposition and subsequently high larval dragonfly abundance in the aquatic community. Finally, high-flower treatments were coupled with changes in zooplankton species richness and shifts in the composition of zooplankton communities. Through changes in animal behavior and trophic interactions in terrestrial and aquatic systems, this work illustrates the broad and potentially cryptic effects of invasive species, and provides additional compelling motivation for ecologists to conduct investigations that cross traditional ecosystem boundaries.     

Nocturnal migration of dragonflies over the Bohai Sea in northern China

Abstract.  1. A sudden increase and subsequent sharp decrease of catches of dragonflies in a searchlight trap, with Pantala flavescens Fabricius (Odonata: Libellulidae) predominating, observed at Beihuang Island in the centre of the Bohai Gulf, in 2003 and 2004, indicated a seasonal migration of these insects over the sea during the night in China. The movements were associated with the onset of fog.
2. Simultaneous radar observations indicated that the nocturnally migrating dragonflies generally flew at altitudes of up to 1000 m above sea level, with high density concentrations at about 200–300 or 500 m; these concentrations were coincident with the temperature inversion.
3. During early summer, the dragonflies oriented in a downwind direction, so that the displacement direction varied between different altitudes. In contrast, during late summer, the dragonflies were able to compensate for wind drift, even headwind drift, so as to orient south-westward no matter how the wind changed, and thus the displacement direction was towards the south-west.
4. The duration of flight, estimated from the variation of area density derived from radar data and hourly catches in the searchlight trap through the night, was about 9–10 h. The displacement speed detected using radar was ≈5–11 m s⁻¹. Therefore, the dragonflies might migrate 150–400 km in a single flight.
5. The dragonflies were thought to originate in Jiangsu province and they migrated into north-east China to exploit the temporary environment of paddy fields in early summer. Their offspring probably migrated back south during late summer and autumn.     

Measurement on Camber Deformation of Wings of Free-flying Dragonflies and Beating-flying Dragonflies

1　IntroductionNumerouskinematicparameters,includingwing beatfrequency ,wingorientation ,andbothspan andchord wisedeformation ,arerelevanttotheaerodynam icanalysisofinsectflight[1,2 ] .Althoughnearlyalltherecentstudiesofinsectflightaerodynamics[3,4 ] haveidentifiedthatthemechanismsrequireflowseparationattheleadingedge ,andcamberisnotexpectedtohaveanysignificantinfluenceonthemagnitudeoftheforcecoefficient,someinsects ,suchasdragonfliesandbut terflies,frequently glideusinglowanglesofattack ,lead…     

Eye movements and target fixation during dragonfly prey-interception flights

The capture of flying insects by foraging dragonflies is a highly accurate, visually guided behavior. Rather than simply aiming at the prey’s position, the dragonfly aims at a point in front of the prey, so that the prey is intercepted with a relatively straight flight trajectory. To better understand the neural mechanisms underlying this behavior, we used high-speed video to quantify the head and body orientation of dragonflies (female Erythemis simplicicollis flying in an outdoor flight cage) relative to an artificial prey object before and during pursuit. The results of our frame-by-frame analysis showed that during prey pursuit, the dragonfly adjusts its head orientation to maintain the image of the prey centered on the “crosshairs” formed by the visual midline and the dorsal fovea, a high acuity streak that crosses midline at right angles about 60° above the horizon. The visual response latencies to drifting of the prey image are remarkably short, ca. 25 ms for the head and 30 ms for the wing responses. Our results imply that the control of the prey-interception flight must include a neural pathway that takes head position into account.     

The effects of a wind farm on birds in a migration point: the Strait of Gibraltar

The interaction between birds and wind turbines is an important factor to consider when a wind farm is constructed. A wind farm and two control areas were studied in Tarifa (Andalusia Province, southern Spain, 30STF590000–30STE610950). Variables were studied along linear transects in each area and observations of flight were also recorded from fixed points in the wind farm. The main purpose of our research was to determine the impact and the degree of flight behavioural change in birds flights resulting from a wind farm. Soaring birds can detect the presence of the turbines because they change their flight direction when they fly near the turbines and their abundance did not seem to be affected. This is also supported by the low amount of dead birds we found in the whole study period in the wind farm area. More studies will be necessary after and before the construction of wind farms to assess changes in passerine populations. Windfarms do not appear to be more detrimental to birds than other man-made structures.     

Home Range,Movement, and Distribution Patterns of the Threatened Dragonfly Sympetrum depressiusculum (Odonata: Libellulidae): A Thousand Times Greater Territory to Protect?

Dragonflies are good indicators of environmental health and biodiversity. Most studies addressing dragonfly ecology have focused on the importance of aquatic habitats, while the value of surrounding terrestrial habitats has often been overlooked. However, species associated with temporary aquatic habitats must persist in terrestrial environments for long periods. Little is known about the importance of terrestrial habitat patches for dragonflies, or about other factors that initiate or influence dispersal behaviour. The aim of this study was to reveal the relationship between population dynamics of the threatened dragonfly species Sympetrum depressiusculum at its natal site and its dispersal behaviour or routine movements within its terrestrial home range. We used a mark–release–recapture method (marking 2,881 adults) and exuviae collection with the Jolly–Seber model and generalized linear models to analyse seasonal and spatial patterns of routine movement in a heterogeneous Central European landscape. Our results show that utilisation of terrestrial habitat patches by adult dragonflies is not random and may be relatively long term (approximately 3 mo). Adult dragonflies were present only in areas with dense vegetation that provided sufficient resources; the insects were absent from active agricultural patches (p = 0.019). These findings demonstrate that even a species tightly linked to its natal site utilises an area that is several orders of magnitude larger than the natal site. Therefore, negative trends in the occurrence of various dragonfly species may be associated not only with disturbances to their aquatic habitats, but also with changes in the surrounding terrestrial landscape.     

Why are wasps so intimidating: field experiments on hunting dragonflies (Odonata: Aeshna grandis)

The mechanisms of aposematism (unprofitability of prey combined with a conspicuous signal) have mainly been studied with reference to vertebrate predators, especially birds. We investigated whether dragonflies, Aeshna grandis, avoid attacking wasps, Vespula norwegica, which are an unprofitable group of prey for most predators. As a control we used flies that were painted either black or with yellow and black stripes. The dragonflies showed greater aversion to wasps than to flies. Black-and-yellow-striped flies were avoided more than black ones, suggesting that aposematic coloration on a harmless fly provides a selective advantage against invertebrate predators. There was no significant difference in reactions to black-painted and black-and-yellow wasps, indicating that, in addition to coloration, some other feature in wasps might deter predators. In further experiments we offered dragonflies artificial prey items in which the candidate warning signals (coloration, odour and shape) were tested separately while other confounding factors were kept constant. The dragonflies avoided more black-and-yellow prey items than solid black or solid yellow ones. However, we found no influence of wasp odour on dragonfly hunting. Dragonflies were slightly, but not significantly, more reluctant to attack wasp-shaped prey items than fly-shaped ones. Our results suggest that the typical black-and-yellow stripes of wasps, possibly combined with their unique shape, make dragonflies avoid wasps. Since black-and-yellow stripes alone significantly decreased attack rate, we conclude that even profitable prey species (i.e. Batesian mimics) are able to exploit the dragonflies' avoidance of wasps. Copyright 2003 Published by Elsevier Ltd on behalf of The Association for the Study of Animal Behaviour.      

The impacts of habitat disturbance on adult and larval dragonflies (Odonata) in rainforest streams in Sabah,Malaysian Borneo

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Morning flight behavior of nocturnally migrating birds along the western basin of Lake Erie

Many species of birds that normally migrate during the night have been observed engaging in so‐called morning flights during the early morning. The results of previous studies have supported the hypothesis that one function of morning flights is to compensate for wind drift that birds experienced during the night. Our objective was to further explore this hypothesis in a unique geographic context. We determined the orientation of morning flights along the southern shore of Lake Erie's western basin during the spring migrations of 2016 and 2017. This orientation was then compared to the observed orientation of nocturnal migration. Additionally, the orientation of the birds engaged in morning flights following nights with drifting winds was compared to that of birds following nights with non‐drifting winds. The morning flights of most birds at our observation site were oriented to the west‐northwest, following the southern coast of Lake Erie. Given that nocturnal migration was oriented generally east of north, the orientation of morning flight necessarily reflected compensation for accumulated, seasonal wind drift resulting from prevailingly westerly winds. However, the orientation of morning flights was similar following nights with drifting and non‐drifting winds, suggesting that birds on any given morning were not necessarily re‐orienting as an immediate response to drift that occurred the previous night. Given the topographical characteristics of our observation area, the west‐northwest movement of birds in our study is likely best explained as a more complex interaction that could include some combination of compensation for wind drift, a search for suitable stopover habitat, flying in a direction that minimizes any loss in progressing northward toward the migratory goal, and avoidance of a lake crossing.     

Effect of Adult Experience on in-Flight Orientation to Plant and Plant–Host Complex Volatiles inAphidius erviHaliday (Hymenoptera, Braconidae)

The effect of adult experience on in-flight orientation to plant–host complex volatiles byAphidius erviHaliday was studied in a wind tunnel bioassay, usingAcyrthosiphon pisum(Harris), maintained on broad bean plants (Vicia faba) as host. A short oviposition experience (15 s) on the plant–host complex (PHC) was sufficient to induce a drastic decrease of flight propensity and stimulated a foraging behavior characterized by intense walking activity. However, flight activity resumed to normal levels 1 h after the oviposition experience on the PHC occurred. For parasitoids conditioned on the PHC for at least 1 min the recorded proportion making oriented flights to the PHC was significantly higher than that for naive females. In contrast, oviposition experience in the absence of plant material did not influence theA. erviflight response. Oviposition attempts on aphid dummies without egg release did not reduce flight activity. WhenA. ervifemales were exposed to glass beads coated withAc. pisumcornicle secretion, a priming effect was observed, resulting, compared with naive females, in a significantly higher rate of oriented flights to the PHC. In contrast, oviposition attempts visually induced by colored aphid dummies did not influence flight behavior. A strong reaction to volatile cues from uninfested plants was induced by oviposition experience on newly infested broad bean plants. This appears to be a case of associative learning. In fact, uninfested broad bean plants are basically unattractive to naiveA. ervifemales. The results demonstrate that adult experience has a considerable influence onA. ervibehavior and may have important implications for biological control of natural pest aphid populations.     

Oviposition site selection and effect of meteorological conditions on flight of Eudonia sabulosella (Lepidoptera: Scopariinae) with implications for pasture damage

Abstract

Eudonia sabulosella (Walker) is economically the most important hill country sod webworm in New Zealand. Female moths selected long, sparse pasture cover for oviposition. Adult flight patterns were assessed in relation to meteorological factors (temperature, humidity, rainfall, barometric pressure, wind speed and direction, and cloud cover) as well as lunar cycle phase. Moths were responsive to wind speed and direction, aggregating on slopes from east through south to west (i.e., 180° arc) particularly those of SW orientation, at wind speeds of ≤ 10 km/h. At higher wind speeds adults were confined to leeward slopes only within the 180° arc. Light rain was correlated with increased flight and oviposition. In sites where rainfall coincided with strong winds which confined adults, especially over favourable (long, sparse) pasture types, much oviposition occurred. Grasses in these sites were susceptible to larval sod webworm feeding damage several months later. Pasture management to remove the favoured sward type may therefore constitute an effective means of pest control for E. sabulosella on hill country.