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Eumenine wasps are not known to be migratory and have never been proposed as migrants, let alone documented as such. We document a large-scale migration of a common eumenine, Ancistrocerus adiabatus, during which 44 000–68 000 wasps moved through a known migration corridor in southwestern Ontario, Canada, in less than an hour. Evidence for migration of another eumenine, Pachodynerus erynnis, six species of flower flies (Diptera, Syrphidae), and two dragonflies (Odonata) is also provided. We hope that this note encourages naturalists to focus their attention on insects at known migration concentration sites to learn more about this grossly understudied aspect of animal behaviour.

Migratory connectivity describes the degree of linkage between different parts of an animal’s migratory range due to the movement trajectories of individuals. High connectivity occurs when individuals from one particular part of the migratory range move almost exclusively to another localized part of the migratory range with little mixing with individuals from other regions. Conversely, low migratory connectivity describes the situation where individuals spread over a wide area during migration and experience a large degree of mixing with individuals from elsewhere. The migratory connectivity concept is frequently applied to vertebrate migrants (especially birds), and it is highly relevant to conservation and management of populations. However, it is rarely employed in the insect migration literature, largely because much less is known about the migration circuits of most migratory insects than is known about birds. In this review, we discuss the applicability of the migratory connectivity concept to long-range insect migrations. In contrast to birds, insect migration circuits typically comprise multigenerational movements of geographically unstructured (non-discrete) populations between broad latitudinal zones. Also, compared to the faster-flying birds, the lower degree of control over movement directions would also tend to reduce connectivity in many insect migrants. Nonetheless, after taking account of these differences, we argue that the migratory connectivity framework can still be applied to insects, and we go on to consider postulated levels of connectivity in some of the most intensively studied insect migrants. We conclude that a greater understanding of insect migratory connectivity would be of value for conserving threatened species and managing pests.

Many lepidopteran species rely upon active flight to migrate over long distances, thus pursuing ephemeral resources, colonizing new habitats, or escaping adverse meteorological conditions. Though their biology and ecology are often well studied, there is only scant information on their wingbeat frequency (WBF), a key aerodynamic determinant of insect flight. In this study, we assessed interspecific and seasonal variability in WBF for 85 different migratory species of Lepidoptera (11 families) under the laboratory conditions of 25 ± 1°C and 75 ± 5% RH. WBF of migrant individuals ranged between 6.7 and 84.5 Hz and substantial interspecific differences were recorded, with members of the Bombycidae exhibiting the highest mean WBFs (i.e., 55.1 ± 1.0 Hz) and Saturniidae the lowest (8.5 ± 0.2 Hz). At a species level, seasonal variation was observed in WBF for Mythimna separata (Walker) (Lepidoptera: Noctuidae), Scotogramma trifolii Rottemberg (Lepidoptera: Noctuidae), and Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae). Our findings add to the scientific knowledge on flight biology of migratory insects, facilitate (automatic) monitoring and population forecasting, and can have broader implications for insect pest management or biodiversity conservation.

Vast numbers of insects annually engage in trans-latitudinal migration and thereby impact structure and functioning of natural and man-made ecosystems. In eastern Asia, long-distance migration has historically been studied for single insect species rather than diverse species complexes. Here, we assessed migration dynamics of multiple economically important migratory species on an island in the Bohai Strait, China. Drawing upon 15-year trapping records of > 2.5 million specimens, we unveil inter- and intra-annual shifts in the species composition and abundance of migrant individuals. Migrants belonged to 9 orders and 36 families, primarily consisting of Lepidoptera (79% individuals), Odonata (8%), and Coleoptera (4%). Seven crop-feeding noctuids, e.g.,Helicoverpa armigera(Hübner),Mythimna separata(Walker), represented 54% of the total trapping records. Trap catches exhibited marked seasonal variation, with the highest capture rate during early fall. Yearly abundance of migratory noctuids was coupled with that of their associated natural enemies. Although overall trap catches did not decrease over the monitoring period, the entire order of Odonata experienced a 14.1% annual rate of decline. Furthermore, 19 out of 108 species exhibited a progressively declining abundance over time, including the cosmopolitan cutwormAgrotis ipsilon(Hufnagel) and the insectivorous dragonflyPantala flavescensFabricius. Our work provides unprecedented insights into insect migration dynamics in eastern Asia, helps fine-tune forecasting and early-warning systems of crop pests, and thereby guides integrated pest management within local agro-landscapes. Also, a long-term tracking of migrant insect populations can shine light on the fate of (insect-mediated) ecosystem services and trophic dynamic processes at a macroscale.

Each year, massive numbers of insects fly across the continents at heights of hundreds of meters, carried by the wind, bringing both environmental benefits and serious economic and social costs. To investigate the insects' flight behavior and their response to winds, entomological radar has proved to be a particularly valuable tool; however, its observations of insect orientation are ambiguous with regard to the head/tail direction, and this greatly hinders interpretation of the migrants' flight behavior. We have developed two related methods of using wind data to resolve the head/tail ambiguity, and we have compared their outputs with those from simply assigning the heading direction to be that which is closer to the track direction. We applied all three methods to observations of Australian plague locust migrations made with an insect monitoring radar. For the study dataset, some of the headings selected by the simpler method are shown to be clearly incorrect. The two new methods generally agree and reveal a significantly different, and presumably more accurate, relationship of heading direction to track direction. However, use of these methods leads to quite a large proportion of the sample being lost because the wind values, which derive from a regional‐scale numerical model, are shown to be incompatible with the radar observations. This exploratory study has moreover demonstrated that locusts are frequently oriented at a large angle to their track and that quite often their movement is at least slightly tailfirst. Both new methods appear to be a significant improvement on the simpler method. As well as providing an accurate representation of migratory flight behavior, they allow occasions when the model wind values are unreliable to be eliminated from the data sample.

Insect migration redistributes enormous quantities of biomass, nutrients and species globally. A subset of insect migrants perform extreme long-distance journeys, requiring specialized morphological, physiological and behavioral adaptations. The migratory globe skimmer dragonfly (Pantala flavescens) is hypothesized to migrate from India across the Indian Ocean to East Africa in the autumn, with a subsequent generation thought to return to India from East Africa the following spring. Using an energetic flight model and wind trajectory analysis, we evaluate the dynamics of this proposed transoceanic migration, which is considered to be the longest regular non-stop migratory flight when accounting for body size. The energetic flight model suggests that a mixed strategy of gliding and active flapping would allow a globe skimmer to stay airborne for up to 230–286 h, assuming that the metabolic rate of gliding flight is close to that of resting. If engaged in continuous active flapping flight only, the flight time is severely reduced to ∼4 h. Relying only on self-powered flight (combining active flapping and gliding), a globe skimmer could cross the Indian Ocean, but the migration would have to occur where the ocean crossing is shortest, at an exceptionally fast gliding speed and with little headwind. Consequently, we deem this scenario unlikely and suggest that wind assistance is essential for the crossing. The wind trajectory analysis reveals intra- and inter-seasonal differences in availability of favorable tailwinds, with only 15.2% of simulated migration trajectories successfully reaching land in autumn but 40.9% in spring, taking on average 127 and 55 h respectively. Thus, there is a pronounced requirement on dragonflies to be able to select favorable winds, especially in autumn. In conclusion, a multi-generational, migratory circuit of the Indian Ocean by the globe skimmer is shown to be achievable, provided that advanced adaptations in physiological endurance, behavior and wind selection ability are present. Given that migration over the Indian Ocean would be heavily dependent on the assistance of favorable winds, occurring during a relatively narrow time window, the proposed flyway is potentially susceptible to disruption, if wind system patterns were to be affected by climatic change.

In addition to sperm, some accessory substances transferred to females during copulation act as nuptial gifts by passing on valuable nutrients in many insect species. The nutritional status of the males can thus have a great effect on the mating behavior, fecundity and even the longevity of females. However, little is known about the effect of male nutritional status on the female reproductive traits in migratory insect species, particularly when females experience nutrient shortage and have to choose between reproduction and migration. Here, Cnaphalocrocis medinalis, a migratory rice pest in Asia, was studied to explore this issue. Our results showed that in male moths fed with honey solution, their gonads had higher energy content than gonads of starved males, resulting in increased energy content of the bursa copulatrix of females after mating with fed males. Such females showed increased mating frequency, fecundity and longevity compared to females mating with starved males, indicating that male moths deliver nuptial gifts to females and improve their reproductive performance. However, when females were starved, only about 45% mated, with just a single copulation, regardless of male nutritional status. Starved females showed lower fecundity, and a longer pre-oviposition period (indicating a greater propensity to migrate), compared to fed females. However, copulation still significantly extended their longevity. These results suggest that starved females invest in migration to escape deteriorating habitats, rather than investing the nuptial gift to increased fecundity. Our results further our understanding of the reproductive adaptability of migratory insects under conditions of food stress.

Insect populations including butterflies are declining worldwide, and they are becoming an urgent conservation priority in many regions. Understanding which butterfly species migrate is critical to planning for their conservation, because management actions for migrants need to be coordinated across time and space. Yet, while migration appears to be widespread among butterflies, its prevalence, as well as its taxonomic and geographic distribution are poorly understood. The study of insect migration is hampered by their small size and the difficulty of tracking individuals over long distances. Here we review the literature on migration in butterflies, one of the best-known insect groups. We find that nearly 600 butterfly species show evidence of migratory movements. Indeed, the rate of 'discovery' of migratory movements in butterflies suggests that many more species might in fact be migratory. Butterfly migration occurs across all families, in tropical as well as temperate taxa; Nymphalidae has more migratory species than any other family (275 species), and Pieridae has the highest proportion of migrants (13%; 133 species). Some 13 lines of evidence have been used to ascribe migration status in the literature, but only a single line of evidence is available for 92% of the migratory species identified, with four or more lines of evidence available for only 10 species - all from the Pieridae and Nymphalidae. Migratory butterflies occur worldwide, although the geographic distribution of migration in butterflies is poorly resolved, with most data so far coming from Europe, USA, and Australia. Migration is much more widespread in butterflies than previously realised - extending far beyond the well-known examples of the monarch Danaus plexippus and the painted lady Vanessa cardui - and actions to conserve butterflies and insects in general must account for the spatial dependencies introduced by migratory movements.

Despite mass movements of insects being documented for decades, whether dragonflies migrate in Europe has not yet been experimentally tested. Similarly, little is known about the influence of weather on the movement decisions and intensity of dragonflies. Taking advantage of large movements of dragonflies along the Baltic Sea coast of Latvia, we investigated whether European dragonflies showed directed movements indicative of migratory behaviour and how weather influences their movements. First, we performed orientation tests with individual dragonflies of two commonly captured species,AeshnamixtaandSympetrumvulgatum, to determine whether dragonflies showed directed flight and whether flight direction differed from wind direction. BothA.mixtaandS.vulgatumdisplayed a uniform mean southward orientation, which differed from the prevailing overhead wind direction, indicating migratory behaviour. Second, we investigated the influence of weather conditions on the abundance of dragonflies captured. Differences in flight behaviour in relation to weather conditions were observed betweenA.mixtaand the two smallerSympetrumspecies (S.vulgatumandS.sanguineum). Generally, temperature, cloud cover and wind direction were the most important predictors for dragonfly abundance, with temperature positively, and cloud cover negatively, influencing abundance.Aeshna mixtaappeared to select favourable tail winds (northerlies), whereas abundance ofSympetrumincreased with more easterly winds. Our results provide important information on the influence of local weather conditions on the flight behaviour of dragonflies, as well as evidence of dragonfly migration along the Baltic coast.

Eastern North American migratory monarch butterflies (Danaus plexippus) have faced sharp declines over the past two decades. Captive rearing of monarch butterflies is a popular and widely used approach for both public education and conservation. However, recent evidence suggests that captive-reared monarchs may lose their capacity to orient southward during fall migration to their Mexican overwintering sites, raising questions about the value and ethics of this activity undertaken by tens of thousands of North American citizens, educators, volunteers and conservationists each year. We raised offspring of wild-caught monarchs on swamp milkweed (Asclepias incarnata) indoors at 29°C during the day and 23°C at night (~77% RH, 18L:6D), and after eclosion, individuals were either tested in a flight simulator or radio tracked in the wild using an array of automated telemetry towers. While 26% (10/39) of monarchs tested in the flight simulator showed a weakly concentrated southward orientation, 97% (28/29) of the radio-tracked individuals that could be reliably detected by automated towers flew in a south to southeast direction from the release site and were detected at distances of up to 200 km away. Our results suggest that, although captive rearing of monarch butterflies may cause temporary disorientation, proper orientation is likely established after exposure to natural skylight cues.

Significance The painted lady butterfly is an annual migrant to northern regions, but the size of the immigration varies by more than 100-fold in successive years. Unlike the monarch, the painted lady breeds year round, and it has long been suspected that plant-growing conditions in winter-breeding locations drive this high annual variability. However, the regions where caterpillars develop over winter remained unclear. Here, we show for the European summer population that winter plant greenness in the savanna of sub-Saharan Africa is the key driver of the size of the spring immigration. Our results show that painted ladies regularly cross the Sahara Desert and elucidate the climatic drivers of the annual population dynamics., Many latitudinal insect migrants including agricultural pests, disease vectors, and beneficial species show huge fluctuations in the year-to-year abundance of spring immigrants reaching temperate zones. It is widely believed that this variation is driven by climatic conditions in the winter-breeding regions, but evidence is lacking. We identified the environmental drivers of the annual population dynamics of a cosmopolitan migrant butterfly (the painted lady Vanessa cardui) using a combination of long-term monitoring and climate and atmospheric data within the western part of its Afro-Palearctic migratory range. Our population models show that a combination of high winter NDVI (normalized difference vegetation index) in the Savanna/Sahel of sub-Saharan Africa, high spring NDVI in the Maghreb of North Africa, and frequent favorably directed tailwinds during migration periods are the three most important drivers of the size of the immigration to western Europe, while our atmospheric trajectory simulations demonstrate regular opportunities for wind-borne trans-Saharan movements. The effects of sub-Saharan vegetative productivity and wind conditions confirm that painted lady populations on either side of the Sahara are linked by regular mass migrations, making this the longest annual insect migration circuit so far known. Our results provide a quantification of the environmental drivers of large annual population fluctuations of an insect migrant and hold much promise for predicting invasions of migrant insect pests, disease vectors, and beneficial species.

Insects are highly successful animals. They have limited ability to regulate their temperature and therefore will expand range in response to warming temperatures. Climate change and associated rising global temperature is impacting the range and distribution of stinging insects. There is evidence that many species are expanding range toward the poles, primarily in response to warming. With expanded distribution of stinging insects, increased interaction with humans is anticipated with consequently increased rates of sting-related reactions and need for intervention. This article focuses on evidence that insects are expanding their range in response to warming temperature, increasing likelihood of human interaction.

Insect migrations rival those of vertebrates in terms of numbers of migrating individuals and even biomass, although instances of the former are comparatively poorly documented. This is especially true in the world’s tropics, which harbor the vast majority of Earth’s insect species. Understanding these mass movements is of critical and increasing importance as global climate and land use change accelerate and interact to alter the environmental cues that underlie migration, particularly in the tropics. Here, we provide the first evidence for an insect migration for the nymphalid butterfly Panacea prola in the Amazon, the world’s largest and most biodiverse rainforest that is experiencing a shifting climate and rapid forest loss.

Oedaleus asiaticus is one of the dominant species of grasshoppers in the rangeland on the Mongolian plateau, and a serious pest, but its migratory behavior is poorly known. We investigated the take-off behavior of migratory O. asiaticus in field cages in the inner Mongolia region of northern China. The species shows a degree of density-dependent phase polyphenism, with high-density swarming populations characterized by a brown morph, while low-density populations are more likely to comprise a green morph. We found that only 12.4% of brown morphs engaged in migratory take-off, and 2.0% of green morphs. Migratory grasshoppers took off at dusk, especially in the half hour after sunset (20:00&ndash, 20:30 h). Most emigrating individuals did not have any food in their digestive tract, and the females were mated but with immature ovaries. In contrast, non-emigrating individuals rarely had empty digestive tracts, and most females were mated and sexually mature. Therefore, it seems clear that individuals prepare for migration in the afternoon by eliminating food residue from the body, and migration is largely restricted to sexually immature stages (at least in females). Furthermore, it was found that weather conditions (particularly temperature and wind speed at 15:00 h) in the afternoon had a significant effect on take-off that evening, with O. asiaticus preferring to take off in warm, dry and calm weather. The findings of this study will contribute to a reliable basis for forecasting migratory movements of this pest.

The recent introduction and spread of Helicoverpa armigera throughout South America highlight the invasiveness and adaptability of moths in the Helicoverpa genus. Long-range movement in three key members, H. armigera, H. zea, and H. punctigera, occurs by migration and international trade. These movements facilitate high population admixture and genetic diversity, with important economic, biosecurity, and control implications in today's agricultural landscape. This is particularly true for the spread of resistance alleles to transgenic crops expressing Bacillus thuringiensis (Bt) toxins that are planted over vast areas to suppress Helicoverpa spp. The ability to track long-distance movement through radar technology, population genetic markers, and/or long-distance dispersal modeling has advanced in recent years, yet we still know relatively little about the population trajectories or migratory routes in Helicoverpa spp. Here, we consider how experimental and theoretical approaches can be integrated to fill key knowledge gaps and assist management practices.

Many insects such as the crop pest Agrotis ipsilon (black cutworm) migrate seasonally to exploit suitable breeding and winter habitats. The migration of a crop pest also increases the risk of sudden outbreaks. Knowledge about insect migration thus is important for developing a forecasting and warning system for migratory pests. Here we used directional flight devices to study the orientation behavior of A. ipsilon in China during the northward and southward migratory periods and showed that the insects during each period exhibited a common cardinal orientation. Northward migratory moths were oriented at an orientation angle mean of 24.4° and the southward at 205.17°. Expression levels of cryptochrome and magnetoreceptor genes in migratory populations were higher than in a reared population and higher in the southward migratory population than in the northward. These findings provide a physiological and molecular basis for further study of the migratory behavior of the black cutworm and potential control of this pest.

1. Every year billions of insects engage in long-distance, seasonal mass migrations which have major consequences for agriculture, ecosystem services and insect-vectored diseases. Tracking this movement in the field is difficult, with mass migrations often occurring at high altitudes and over large spatial scales. 2. As such, tethered flight provides a valuable tool for studying the flight behaviour of insects, giving insights into flight propensity (e.g. distance, duration and velocity) and orientation under controlled laboratory settings. By experimentally manipulating a variety of environmental and physiological traits, numerous studies have used this technology to study the flight behaviour of migratory insects ranging in size from aphids to butterflies. Advances in functional genomics promise to extend this to the identification of genetic factors associated with flight. Tethered flight techniques have been used to study migratory flight characteristics in insects for more than 50years, but have never been reviewed. 3. This study summarises the key findings of this technology, which has been employed in studies of species from six Orders. By providing detailed descriptions of the tethered flight systems, the present study also aims to further the understanding of how tethered flight studies support field observations, the situations under which the technology is useful and how it might be used in future studies. 4. The aim is to contextualise the available tethered flight studies within the broader knowledge of insect migration and to describe the significant contribution these systems have made to the literature.

An outbreak of beet armyworm (Spodoptera exigua (Hubner)), cabbage looper, (Trichoplusia ni (Hubner)), and other noctuid pests devastated cotton production in the Lower Rio Grande Valley, TX, in 1995. Major infestations occurred later in the year several hundred kilometers away in other cotton production areas in Texas and Oklahoma, but information is lacking to connect regional infestations by these migratory pests. The objective of this study was to evaluate the capability of WSR-88D Doppler weather radar in locating and monitoring pest emigration from severely infested areas. Maximum radar reflectivity identified possible source areas in the vicinity of major infestations in cotton by beet armyworms and cabbage loopers that had been reported in Willacy County, TX. Areas of maximum clear-air radar reflectivity 13.5–16.5 dBZ) appeared approximately 0.5 h after sunset and displaced downwind toward susceptible cotton production regions in the Winter Garden and Southern Rolling Plains of west-central TX. Our results suggest that WSR-88D weather radar data may be useful in the development of crop pest advisories that estimate the timing, intensity, and displacement of insect migration flights, especially with recent enhancements in timely public access to WSR-88D radar data and radar data processing and analysis software.

Sometimes, extreme weather is vital for the population survival of migratory insects by causing sudden population collapse or outbreak. Several studies have shown that rice planthopper migration was significantly influenced by typhoons in eastern Asia. Most typhoons occur in the summer, especially in August. In August, brown planthopper Nilaparvata lugens (Stal) migrates northward or southward depending on wind direction, and thus typhoons can potentially influence its migration process and population distribution. However, this has not yet been studied. This paper reported a case study on the effects of Typhoon Soudelor on the summer migration of N. lugens in eastern China in 2015. The migration pathways of N. lugens were reconstructed for the period under the influence of a typhoon by calculating the trajectories and migration events in 8 counties of the Yangtze River Valley region with ancillary information. Trajectory modelling showed that most migrants took short distance migrations (less than 200 km) under the influence of the Typhoon Soudelor. Numerous N. lugens migrants were concentrated and deposited at the rear of the typhoon during the last 5 days of Typhoon Soudelor on August 9–13 due to horizontal convergence, and this led to an outbreak population. These results indicated that the N. lugens population was redistributed by the typhoon in the summer and that the population dynamics at the rear of a typhoon should be kept under close surveillance. This study provided insight into migratory organisms adapting to atmospheric features. This article is protected by copyright. All rights reserved

Migratory insects use a variety of innate mechanisms to determine their orientation and maintain correct bearing. For long-distance migrants, like the monarch butterfly (Danaus plexippus), these journeys could be affected by exposure to environmental contaminants. Neonicotinoids are synthetic insecticides that work by affecting the nervous system of insects resulting in impairment of their mobility, cognitive performance and other physiological and behavioural functions. To examine how neonicotinoids might affect the ability of monarch butterflies to maintain a proper directional orientation on their ∼4,000 km migration, we grew swamp milkweed (Asclepias incarnata) in soil that was either untreated (0 ng/g: control) or mixed with low (15 ng/g of soil), or high (25 ng/g of soil) levels of the neonicotinoid clothianidin. Monarch caterpillars were raised on control or clothianidin-treated milkweed and, after pupation, either tested for orientation in a static flight simulator or radio-tracked in the wild during the fall migration period. Despite clothianidin being detectable in milkweed tissue consumed by caterpillars, there was no evidence that clothianidin influenced the orientation, vector strength (i.e., concentration of direction data around the mean), or the rate of travel of adult butterflies and nor was there evidence that morphological traits (i.e., mass and forewing length), testing time, wind speed, or temperature impacted directionality. While samples sizes for both flight simulator and radio-tracking tests were limited, our preliminary results suggest that clothianidin exposure during early caterpillar development does not affect the directed flight of adult migratory monarch butterflies or influence their orientation at the beginning of migration.

In this contribution we report the observation of an individual of the migrant dragonfly Pantala flavescens (Fabricius, 1798) found at Montanaro (Piemonte, Italy) on 14 Aug 2019. This represents the first record of the species for mainland Italy and one of the very few available for Western and Central Europe before 2019. We discuss two hypotheses on the origin of this individual integrating available literature with very recent records retrieved from citizen science faunistic platforms., Fragmenta Entomologica, Vol. 51 No. 2 (2019)

Migration is a costly strategy in terms of reproduction output. Competition for limited internal resources leads to physiological management of migration-reproduction trade-offs in energy allocation. Migratory insects must choose to determine to allocate energy into reproduction or migration when confronted insufficient energy supply. Although nutrient shortage is known to stimulate insect migration to escape deteriorating habitat, little is known about when and how migratory insects make decisions when confronted by a nutritional shortage. Here Cnaphalocrocis medinalis (Lepidoptera: Pyralidae), a migratory rice pest in eastern Asia, was used to study the effects of starvation on reproductive traits, behavioral traits and energy allocation. The result showed that one or two days&rsquo, starvation before preoviposition did not significantly reduce the fertility (total egg per female laid) and flight capability (flight duration and distance) of both sexes C. medinalis. The preoviposition period was extended significantly only if moths were starved starting on the first day after emergence. Also, take-off percentage of moths starved since their first day increased significantly, and continued to increase even if supplemental nutrients were supplied as honey solution in later days. Moths starved on the first day appeared to allocate or transfer triglycerides into the thorax to maintain the migration process: the quantity of thoracic triglycerides did not differ with age, but abdominal triglycerides decreased with age if starvation continued. These results indicate that the first day post-emergence is a critical period for C. medinalis to decide to migrate or not in response to lack of food. This furthers our understanding of the population dynamics of migratory insects under natural conditions.

Modelling ecological niches of migratory animals requires incorporating a temporal dimension, in addition to space. Here, we introduce an approach to model multigenerational migratory insects using time-partitioned environmental variables (by months and years) and time- and behaviour-partitioned records (breeding records to model reproductive habitat). We apply this methodology to modelling the Palearctic-African migratory cycle of the Painted Lady butterfly (Vanessa cardui), based on data encompassing 36 years (646 breeding sites from 30 countries). Each breeding record is linked to a particular time (month and year), and the associated values of the bioclimatic variables are used for an ensemble modelling strategy, to finally obtain monthly projections. The results show obligated movements, mostly latitudinal, for the species' successive generations across the overall range, and only scattered locations show high probabilities of reproduction year-round. The southernmost reproductive areas estimated for the Palearctic-African migratory pool reach equatorial latitudes from December to February. We thus propose a potential distribution for the winter ‘missing generations' that would expand the V. cardui migration cycle to encompass about 15 000 km in latitude, from northernmost Europe to equatorial Africa. In summer, Europe represents the major temporary resource for V. cardui, while January and February show the lowest overall suitability values, and they are potentially the most vulnerable period for the species to suffer yearly bottlenecks. In summary, we demonstrate the potential of the proposed niche modelling strategy to investigate migratory movements of insects., This work was funded by the Committee for Research and Exploration of the National Geographic Society (grant no. WW1-300R-18), the British Ecological Society (grant no. LRB16/1015), the PRIC grants of the Fundació Barcelona Zoo, and by project CGL2016-76322 (AEI/FEDER, UE) to G.T. G.T. is supported by the MINECO programme Juan de la Cierva Incorporación (IJCI-2016-29083), the Marie Curie Actions FP7-People-2013 IOF (project 622716) and ‘La Caixa' Foundation (grant LCF/BQ/PR19/11700004).

We observed a nocturnal insect swarm aboard the oceanographic ship Cruzeiro do Sul of the Brazilian Navy, while conducting a survey of the Montague guyot (seamount), 389 km distant from the nearest land in the South Atlantic. The insects came from open sea toward the ship from all directions, attracted by the powerful light of the deck. Most insects collided with the hull and fell into the ocean, but we managed to capture and determine 17 (13 Hemiptera of a single species, three Lepidoptera of three species and one Odonata). With one exception, we are certain that none of the specimens caught originated from the ship. The geographic origin, most likely the coast of Brazil, and flight endurance of these insects were inferred using data on wind speed and direction, provided by the crew of the ship, and were reconstructed using Hysplit modeling of air current trajectories.

Geomagnetic field (GMF) intensity can be used by some animals to determine their direction and position during migration. However, its role, if any, in mediating other migration-related phenotypes remains largely unknown. Here, we simulated variation in GMF intensity between two locations along the migration route of a nocturnal insect migrant, the brown planthopper Nilaparvata lugens, that varied by ∼5 μT (GMF50μT vs. GMF45μT) in field intensity. After one generation of exposure, we tested for changes in key morphological, behavioural and physiological traits related to migratory performance including wing dimorphism, flight capacity and positive phototaxis. Our results showed that all three morphological and behavioural phenotypes responded to a small difference in magnetic field intensity between the simulated northern vs. southern locations in ways expected along the migratory route. Consistent magnetic responses in the expression of the phototaxis-related Drosophila-like cryptochrome 1 (Cry1) gene and levels of two primary energy substrates used during flight, triglyceride and trehalose, were also found. Our findings indicate GMF intensity can be a cue that regulates the expression of phenotypes critical for insect migration and highlight the unique role of magnetoreception as a trait that can help migratory insects express potentially beneficial phenotypes in geographically variable environments.

Managing agricultural pests that use multiple host plant species is a challenge when individuals move between host plants in natural vegetation and agricultural environments. The green mirid (Creontiades dilutus) Stål (Hemiptera: Miridae) is endemic to Australia and routinely invades cotton from local uncultivated vegetation, but may also originate from remote locations in the arid continental interior. This bug is polyphagous and highly mobile, which contributes to its pest status in cotton L. (Malvaceae) systems as well as its persistence in arid environments with sparsely distributed ephemeral host plants. The aim of this study was to evaluate how C. dilutus individuals use a variety of host species across remote arid regions and highly managed agricultural landscapes. Structured field surveys spanning vast areas across the Simpson Desert in the arid heart of Australia, as well as subcoastal cotton production systems, were designed to evaluate host use across environments that share few plant species. High numbers of C. dilutus were collected from Cullen australasicum (Schltdl.) J.W.Grimes (Fabaceae) (perennial hosts) and Goodenia cycloptera R.Br. (Goodeniaceae) (ephemeral hosts) in the desert following rain. In agricultural environments, C. dilutus bugs were mostly found on irrigated Medicago sativa L. (Fabaceae) (lucerne), and to a lesser extent Melilotus indicus (L.) All. (Fabaceae) near rivers. Significantly, bugs were on these plants prior to the planting of cotton across all environments surveyed. These data allow inferences relating host use, host abundance, and insect migration to one another to understand the connection that C. dilutus bugs have between arid and agricultural environments.

Despite the fact that migratory insects dominate aerial bioflows in terms of diversity, abundance, and biomass [1, 2, 3, 5, 6], the migration patterns of most species, and the effects of their annual fluxes between high- and low-latitude regions, are poorly known. One important group of long-range migrants that remain understudied is a suite of highly beneficial species of hoverfly in the tribe Syrphini, which we collectively term “migrant hoverflies.” Adults are key pollinators [7, 8, 9, 10] and larvae are significant biocontrol agents of aphid crop pests [11], and thus, it is important to quantify the scale of their migrations and the crucial ecosystem services they provide with respect to energy, nutrient, and biomass transport; regulation of crop pests; and pollen transfer. Such assessments cannot be made by sporadic observations of mass arrivals at ground level, because hoverflies largely migrate unnoticed high above ground. We used insect-monitoring radars [12] to show that up to 4 billion hoverflies (80 tons of biomass) travel high above southern Britain each year in seasonally adaptive directions. The long-range migrations redistribute tons of essential nutrients (nitrogen [N] and phosphorus [P]) and transport billions of pollen grains between Britain and Europe, and locally produced populations consume 6 trillion aphids and make billions of flower visits. Migrant hoverfly abundance fluctuated greatly between years, but there was no evidence of a population trend during the 10-year study period. Considering that many beneficial insects are seriously declining [7, 10, 13, 14, 15, 16, 17, 18, 19], our results demonstrate that migrant hoverflies are key to maintaining essential ecosystem services.

Insects represent the most diverse and functionally important group of flying migratory animals around the globe, yet their small size makes tracking even large migratory species challenging. We attached miniaturized radio transmitters (less than 300 mg) to monarch butterflies (Danaus plexippus) and common green darner dragonflies (Anax junius) and tracked their autumn migratory movements through southern Ontario, Canada and into the United States using an automated array of over 100 telemetry towers. The farthest estimated distance a monarch travelled in a single day was 143 km at a wind-assisted groundspeed of 31 km h−1(8.7 m s−1) and the farthest estimated distance a green darner travelled in a single day was 122 km with a wind-assisted groundspeed of up to 77 km h−1(21.5 m s−1). For both species, increased temperature and wind assistance positively influenced the pace of migration, but there was no effect of precipitation. While limitations to tracking such small animals remain, our approach and results represent a fundamental advance in understanding the natural history of insect migration and environmental factors that govern their movements.

Seasonal weather systems that establish prevailing winds and seasonal rainfall on a large scale largely determine insect migration patterns, especially for micro-insects with completely windborne migration. Recent studies indicated that the summer migration of the brown planthopper (BPH, Nilaparvata lugens) in eastern China is related to the strength and position of the Western Pacific Subtropical High-Pressure (WPSH) system and its associated wind and rainfall patterns. Compared with the BPH, the white-backed planthopper (WBPH, Sogatella furcifera) has a similar diet, analogous body size, and strong long-distance migration ability. Thus, the migration pattern for the WBPH can be speculated to be similar to that of the BPH. However, the migration pattern of the WBPH and how this pattern relates to climatic conditions have scarcely been described. Based on almost three decades of data (1977&ndash, 2003), it was suggested that the WBPH in southern China (south of approximately 27&deg, N) migrates into the middle and lower reaches of the Yangtze River after the abrupt movements of the WPSH in mid-June, similar to the BPH. By contrast, the emigration of the WBPH in southern China begins in late May. Further analysis indicated that the migration of the WBPH in late May and early June was short or unsuccessful due to heavy precipitation during the preflood season in southern China from late May to middle June. The results herein demonstrate the differences in migration patterns between two rice planthoppers in the eastern Asia migration arena. We also provide new information that could assist with forecasting outbreaks and implementing control measures against these migratory pests.

Insect migration is globally ubiquitous and can involve continental-scale movements and complex life histories. Apart from select species of migratory moths and butterflies, little is known about the structure of the annual cycle for migratory insects. Using stable-hydrogen isotope analysis of 852 wing samples from eight countries spanning 140 years, combined with 21 years of citizen science data, we determined the full annual cycle of a large migratory dragonfly, the common green darner ( Anax junius ). We demonstrate that darners undertake complex long-distance annual migrations governed largely by temperature that involve at least three generations. In spring, the first generation makes a long-distance northbound movement (further than 650 km) from southern to northern range limits, lays eggs and dies. A second generation emerges and returns south (further than 680 km), where they lay eggs and die. Finally, a third resident generation emerges, reproducing locally and giving rise to the cohort that migrates north the following spring. Since migration timing and nymph development are highly dependent on temperature, continued climate change could lead to fundamental changes in the biology for this and similar migratory insects.

In a short period, we have observed the rapid expansion of bioenergy, resulting in growth in the area of energy crops. In Europe, willow and poplar growing in short-rotation coppices (SRC) are popular bioenergy crops. Their potential impact on biodiversity has not yet been fully investigated. Therefore, there are many uncertainties regarding whether commercial production can cause environmental degradation and biodiversity impoverishment. One of the aspects examined is the impact of these crops on entomofauna and ecosystem services. The best-studied insect group is ground beetles from the Carabidae family. This work gathers data on biodiversity and the functions of carabids in willow and poplar energy plants. The results of these investigations show that energy SRC plants and Carabidae communities can create a synergistic system of mutual benefits. Willow and poplar plants can be a valuable habitat due to the increased biodiversity of entomofauna. Additionally, SRC creates a transitional environment that allows insect migration between isolated populations. On the other hand, ground beetles are suppliers of ecosystem services and make a significant contribution to the building of sustainable agriculture by pest control, thereby ameliorating damage to field crops.

Simple Summary During the latest upsurge of the desert locust, swarms in northern Pakistan and India approached the Chinese border areas. In view of the recent windborne movement into China of another very serious migratory pest, the fall armyworm moth, we investigated the risk of the desert locust invading China. Our analysis shows that China is not likely to experience invasions of desert locust swarms (except, possibly, very marginal incursions on the Nepal border) and there was no likelihood that desert locust would become established in China over the next few decades. Abstract Recently, the most serious upsurge of the desert locust (Schistocerca gregaria) in the last 25 years is spreading across eastern Africa and southwestern Asia. Parts of the desert locust ‘invasion area’, namely the northern border areas of Pakistan and India, are very close to China, and whether locust swarms will invade China is of wide concern. To answer this question, we identified areas of potentially suitable habitat for the desert locust within China based on historical precipitation and temperature data, and found that parts of Xinjiang and Inner Mongolia provinces could provide ephemeral habitat in summer, but these places are remote from any other desert locust breeding areas. New generation adults of the desert locust in Pakistan and India present since April led to swarms spreading into the Indo-Pakistan border region in June, and so we examined historical wind data for this period. Our results showed that winds at the altitude of locust swarm flight blew eastward during April–June, but the wind speeds were quite slow and would not facilitate desert locust eastward migration over large distances. Simulated trajectories of desert locust swarms undertaking 10-day migrations mostly ended within India. The most easterly point of these trajectories just reached eastern India, and this is very close to the eastern border of the invasion area of desert locusts described in previous studies. Overall, the risk that the desert locust will invade China is very low.

Large migrating insects, flying at high altitude, often exhibit complex behaviour. They frequently elect to fly on winds with directions quite different from the prevailing direction, and they show a degree of common orientation, both of which facilitate transport in seasonally beneficial directions. Much less is known about the migration behaviour of smaller (10–70 mg) insects. To address this issue, we used radar to examine the high-altitude flight of hoverflies (Diptera: Syrphidae), a group of day-active, medium-sized insects commonly migrating over the UK. We found that autumn migrants, which must move south, did indeed show migration timings and orientation responses that would take them in this direction, despite the unfavourability of the prevailing winds. Evidently, these hoverfly migrants must have a compass (probably a time-compensated solar mechanism), and a means of sensing the wind direction (which may be determined with sufficient accuracy at ground level, before take-off). By contrast, hoverflies arriving in the UK in spring showed weaker orientation tendencies, and did not correct for wind drift away from their seasonally adaptive direction (northwards). However, the spring migrants necessarily come from the south (on warm southerly winds), so we surmise that complex orientation behaviour may not be so crucial for the spring movements.

Insects account for a large portion of Earth's biodiversity and are key players for ecosystems, notably as pollinators. While insect migration is suspected to represent a natural phenomenon of major importance, remarkably little is known about it, except for a few flagship species. The reason for this situation is mainly due to technical limitations in the study of insect movement. Here, we propose using metabarcoding of pollen carried by insects as a method for tracking their migrations. We developed a flexible and simple protocol allowing efficient multiplexing and not requiring DNA extraction, one of the most time¿consuming part of metabarcoding protocols, and apply this method to the study of the long¿distance migration of the butterfly Vanessa cardui, an emerging model for insect migration. We collected 47 butterfly samples along the Mediterranean coast of Spain in spring and performed metabarcoding of pollen collected from their bodies to test for potential arrivals from the African continent. In total, we detected 157 plant species from 23 orders, most of which (82.8%) were insect¿pollinated. Taxa present in Africa¿Arabia represented 73.2% of our data set, and 19.1% were endemic to this region, strongly supporting the hypothesis that migratory butterflies colonize southern Europe from Africa in spring. Moreover, our data suggest that a northwards trans¿Saharan migration in spring is plausible for early arrivals (February) into Europe, as shown by the presence of Saharan floristic elements. Our results demonstrate the possibility of regular insect¿mediated transcontinental pollination, with potential implications for ecosystem functioning, agriculture and plant phylogeography., GT is supported by the Marie Curie Actions FP7‐People‐2013 IOF (project 622716) and by the MINECO programme Juan de la Cierva Incorporación (IJCI‐2016‐29083). Funding was provided by the statutory funds of W. Szafer Institute of Botany, Polish Academy of Sciences to TS and MR, by the British Ecological Society (grant LRB16/1015) to GT, by project CGL2016‐76322 (AEI/FEDER, UE) and by the Committee for Research and Exploration of the National Geographic Society (grant WW1‐300R‐18) to GT and RV.

Partial migration, where a proportion of a population migrates, while other individuals remain resident, is widespread across most migratory lineages. However, the mechanisms driving individual differences in migratory tendency are still relatively poorly understood in most taxa, but may be influenced by morphological, physiological, and behavioral traits, controlled by phenotypic plasticity and the underlying genetic complex. Insects differ from vertebrates in that partial migration is often associated with pronounced morphological differences between migratory and resident phenotypes, such as wing presence or length. In contrast, the mechanisms influencing migratory tendency in wing-monomorphic insects is less clear. Insects are the most abundant and diverse group of terrestrial migrants, with trillions of animals moving across the globe annually, and understanding the drivers and extent of partial migration across populations will have considerable implications for ecosystem services, such as the management of pests and the conservation of threatened or beneficial species. Here, we present an overview of our current but incomplete knowledge of partial migration in insects. We discuss the factors that lead to the maintenance of partial migration within populations, and the conditions that may influence individual decision making, particularly in the context of individual fitness and reproductive tradeoffs. Finally, we highlight current gaps in knowledge and areas of future research that should prove fruitful in understanding the ecological and evolutionary drivers, and consequences of partial migration in insects. published

The seasonal migration of huge numbers of hoverflies is frequently reported in Europe from mountain passes or spurs of land. The movement of such large numbers of beneficial insects is thought to provide significant ecosystem services in terms of pollination and pest control. Observations from the East Coast of the USA during the 1920s indicate the presence of migratory life histories among some hoverfly species there, but 90 years have now passed since the last reported observation of hoverfly migration in the USA. Here, we analyse video footage taken during a huge northward migration of hoverflies on 20 April 2017 on the West Coast of California. The quantification of migrant numbers from this footage allows us to estimate the passage of over 100 000 hoverflies in half an hour over a 200 m section of headland in Montaña de Oro State Park (San Luis Obispo County). Field collections and analysis of citizen science data indicate different species from the previously reported Eristalis tenax migrations on the East Coast of the USA and provide evidence for migration among North American hoverflies. We wish to raise awareness of this phenomenon and suggest approaches to advance the study of hoverfly migration in North America and elsewhere.

Geomagnetic field (GMF) intensity can be used by some animals to determine their position during migration. However, its role, if any, in mediating other migration-related phenotypes remains largely unknown. Here, we simulated variation in GMF intensity between two locations along the migration route of a nocturnal insect migrant, the brown planthopper Nilaparvata lugens , that varied by approximately 5 µT in field intensity. After one generation of exposure, we tested for changes in key morphological, behavioural and physiological traits related to migratory performance, including wing dimorphism, flight capacity and positive phototaxis. Our results showed that all three morphological and behavioural phenotypes responded to a small difference in magnetic field intensity. Consistent magnetic responses in the expression of the phototaxis-related Drosophila-like cryptochrome 1 ( Cry1 ) gene and levels of two primary energy substrates used during flight, triglyceride and trehalose, were also found. Our findings indicate changes in GMF intensity can alter the expression of phenotypes critical for insect migration and highlight the unique role of magnetoreception as a trait that may help migratory insects express potentially beneficial phenotypes in geographically variable environments.

Pantala flavescens (Fabricius 1798) (Odonata: Libellulidae) is one of the most common species of migratory dragonflies. P. flavescens adults were captured by a searchlight trap on Beihuang Island (BH Island; 38°24'N, 120°55'E) from 2003 to 2016, where there is no freshwater. This inspired our research to analyze the pattern of seasonal migration and population dynamics. Stable hydrogen isotope measurement and the Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) were used to simulate the migration pathway of P. flavescens between different breeding habitats. The results showed that there was no significant difference among population numbers of this overseas migration across years (F13, 2161 = 0.85, P = 0.604); however, the numbers were significantly different across months (F5, 2161 = 3.91, P = 0.003). Our geospatial natal assignment model suggested that P. flavescens trapped on BH were originated in different geographical regions and might have three movement strategies: wandering around northern China and north-bound (positive) and south-bound (negative) movements. Among them, the majority were engaged in wandering around northern China. Model simulations suggested that P. flavescens toured around BH. The results contribute to the knowledge of P. flavescens population ecology in a large-scale geographic region and will aid in the prediction and interpretation of insect migration patterns in response to climate change.

Aim: To determine the importance of different biogeographical processes (vicariance, dispersal, long-distance dispersal and establishment or LDDE) for the current distribution of metalmark moths, a group of small insects, using a time-calibrated molecular tree. Location: Global. Methods: We sampled 104 species of metalmark moths with representatives from all six major biogeographical regions of the world (Afrotropical, Australasian, Neotropical, Nearctic, Oriental and Palaearctic). The taxon sampling includes c. 20% of known species in the family and covers both subfamilies. Using an eight-locus molecular data set and secondary calibration points, we inferred a time-calibrated tree, which was then used for ancestral range estimation with variants of the dispersal-extinction-cladogenesis model (DEC), some of which incorporated the founder-event j-parameter for modelling of LDDEs (DECj). Results: The inferred phylogeny is well resolved and in accordance with earlier works. The metalmark moth distribution is best explained with DECj models. It remains unclear what the ancestral area was. Different models differ in the number and type of events estimated - DEC models infer vicariance for several nodes where DECj models usually infer LDDEs. However, the pattern that emerges from all the analyses is that dispersal and/or LDDE over transoceanic distances such as between the Afrotropics and Australasia and the Afrotropics and Neotropics occurred several times in the evolutionary history of this group. Main conclusions: Vicariance may have played an important role in the early evolution of metalmark moths, while dispersal and LDDEs mostly shaped the group's distribution later on. Based on insect flight research using aerial radars, the best mechanism for explaining how small insects cross oceans is by being adapted for exploiting atmospheric conditions as opposed to employing active flight. (Less)

Fall armyworm, Spodoptera frugiperda (J.E. Smith), is a highly mobile insect pest of a wide range of host crops. However, this pest of tropical origin cannot survive extended periods of freezing temperature but must migrate northward each spring if it is to re-infest cropping areas in temperate regions. The northward limit of the winter-breeding region for North America extends to southern regions of Texas and Florida, but infestations are regularly reported as far north as Québec and Ontario provinces in Canada by the end of summer. Recent genetic analyses have characterized migratory pathways from these winter-breeding regions, but knowledge is lacking on the atmosphere's role in influencing the timing, distance, and direction of migratory flights. The Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model was used to simulate migratory flight of fall armyworm moths from distinct winter-breeding source areas. Model simulations identified regions of dominant immigration from the Florida and Texas source areas and overlapping immigrant populations in the Alabama-Georgia and Pennsylvania-Mid-Atlantic regions. This simulated migratory pattern corroborates a previous migratory map based on the distribution of fall armyworm haplotype profiles. We found a significant regression between the simulated first week of moth immigration and first week of moth capture (for locations which captured ≥ 10 moths), which on average indicated that the model simulated first immigration 2 weeks before first captures in pheromone traps. The results contribute to knowledge of fall armyworm population ecology on a continental scale and will aid in the prediction and interpretation of inter-annual variability of insect migration patterns including those in response to climatic change and adoption rates of transgenic cultivars.

Vector-borne animal diseases pose a continuous and substantial threat to livestock economies around the globe. Increasing international travel, the globalisation of trade, and climate change are likely to play a progressively more important role in the introduction, establishment and spread of arthropod-borne pathogens worldwide. A review of the literature reveals that many climatic variables, functioning singly or in combination, exert varying effects on the distribution and range of Culicoides vector midges and mosquitoes. For example, higher temperatures may be associated with increased insect abundance--thereby amplifying the risk of disease transmission--but there are no indications yet of dramatic shifts occurring in the geographic range of Culicoides midges. However, the same cannot be said for mosquitoes: over the last few decades, multiple Asian species have established themselves in Europe, spread and are unlikely to ever be eradicated. Research on how insects respond to changes in climate is still in its infancy. The authors argue that we need to grasp how other annectant changes, such as extremes in precipitation (drought and flooding), may affect the dispersal capability of mosquitoes. Models are useful for assessing the interplay between mosquito vectors expanding their range and the native flora and fauna; however, ecological studies employing classical mark-release-recapture techniques remain essential for addressing fundamental questions about the survival and dispersal of mosquito species, with the resulting parameters fed directly into new-generation disease transmission models. Studies on the eventual impact of mosquitoes on animal and human health should be tackled through large-scale integrated research programmes. Such an approach calls for more collaborative efforts, along the lines of the One Health Initiative.

Autumn remains a relatively neglected season in climate change research in temperate and arctic ecosystems. This neglect occurs despite the importance of autumn events, including leaf senescence, fruit ripening, bird and insect migration, and induction of hibernation and diapause. Changes in autumn phenology alter the reproductive capacity of individuals, exacerbate invasions, allow pathogen amplification and higher disease-transmission rates, reshuffle natural enemy-prey dynamics, shift the ecological dynamics among interacting species, and affect the net productivity of ecosystems. We synthesize some of our existing understanding of autumn phenology and identify five areas ripe for future climate change research. We provide recommendations to address common pitfalls in autumnal research as well as to support the conservation and management of vulnerable ecosystems and taxa.

Migration has evolved among many animal taxa and migratory species are found across all major lineages. Insects are the most abundant and diverse terrestrial migrants, with trillions of animals migrating annually. Partial migration, where populations consist of resident and migratory individuals, is ubiquitous among many taxa. However, the underlying mechanisms are relatively poorly understood and may be driven by physiological, behavioural or genetic variation within populations. We investigated the differences in migratory tendency between migratory and resident phenotypes of the hoverfly, Episyrphus balteatus , using tethered flight mills. Further, to test whether migratory flight behaviour is heritable and to disentangle the effects of environment during development, we compared the flight behaviour of laboratory-reared offspring of migrating, overwintering and summer animals. Offspring of migrants initiated more flights than those of resident individuals. Interestingly, there were no differences among wild-caught phenotypes with regard to number of flights or total flight duration. Low activity in field-collected migrants might be explained by an energy-conserving state that migrants enter into when under laboratory conditions, or a lack of suitable environmental cues for triggering migration. Our results strongly suggest that flight behaviour is heritable and that genetic factors influence migratory tendency in E. balteatus . These findings support the growing evidence that genetic factors play a role in partial migration and warrant careful further investigation.

Myriad tiny insect species take to the air to engage in windborne migration, but entomology also has its 'charismatic megafauna' of butterflies, large moths, dragonflies and locusts. The spectacular migrations of large day-flying insects have long fascinated humankind, and since the advent of radar entomology much has been revealed about high-altitude night-time insect migrations. Over the last decade, there have been significant advances in insect migration research, which we review here. In particular, we highlight: (1) notable improvements in our understanding of lepidopteran navigation strategies, including the hitherto unsuspected capabilities of high-altitude migrants to select favourable winds and orientate adaptively, (2) progress in unravelling the neuronal mechanisms underlying sun compass orientation and in identifying the genetic complex underpinning key traits associated with migration behaviour and performance in the monarch butterfly, and (3) improvements in our knowledge of the multifaceted interactions between disease agents and insect migrants, in terms of direct effects on migration success and pathogen spread, and indirect effects on the evolution of migratory systems. We conclude by highlighting the progress that can be made through inter-phyla comparisons, and identify future research areas that will enhance our understanding of insect migration strategies within an eco-evolutionary perspective.

High-altitude nocturnal insect migrations are ubiquitous and represent significant pulses of biomass, which impact large areas and multiple trophic levels, yet are difficult to study and poorly understood. Predation on migratory insects by high-flying bats provides potential for investigating flows of migratory insects across a landscape. Brazilian free-tailed bats, Tadarida brasiliensis, provide valuable ecosystem services by consuming migratory pests, and research suggests migratory insects are an important resource to bats in autumn. We sequenced insect DNA from bat feces collected during the 2010–2012 autumn migrations of insects over southern Texas, and tested the utility of predator–prey interactions for monitoring migratory insect populations by asking: 1) how extensively do bats consume migratory insects during autumn? (2) does the prey community reflect known drivers of insect migrations, e.g. cold fronts? and (3) are migratory insects increasingly important to bats when local food resources decline in autumn? Bats consumed at least 21 species of migratory insects and 44 species of agricultural pests. Prey community richness increased with cold front passage. Bats consumed migratory moths over the entire autumn season, and the proportion of migratory moths in the bat diet increased over the course of the autumn season in all 3 years. This study confirms extensive consumption of migratory insects by bats, links patterns in prey communities to mechanisms driving insect migration, and documents a novel approach to tracking patterns of migratory insect movement. As an important resource for T. brasiliensis in autumn, migratory insects provide stabilizing effects to the local animal community.