Insect Migration Research Articles

Bat activity correlated with migratory insect bioflows in the Pyrenees.

High altitude mountain passes in the Pyrenees are known to be important migratory hotspots for autumn migrating insects originating from large swathes of northern Europe. In the Pyrenees, prior research has focused on diurnal migratory insects. In this study, we investigate the nocturnal component of the migratory assemblage and ask if this transient food source is also used by bat species. Three seasons of insect trapping revealed 66 species of four different orders, 90% of which were Noctuid moths, including the destructive pest Helicoverpa armigera, otherwise known as the cotton bollworm. Acoustic bat detectors revealed that high activity of Nyctalus spp. and Tadarida teniotis bats were closely synchronized with the arrival of the migratory moths, suggesting this food source is important for both resident and migratory bats to build or maintain energy reserves. Bats of the Nyctalus spp. are likely migrating through the study site using fly-and-forage strategies or stopping over in the area, while resident T. teniotis may be exploiting the abundant food source to build fat stores for hibernation. This study shows that nocturnal migratory insects are abundant in the Pyrenees during autumn and interact during migration, not only with their co-migrant bats but also with resident bat species.

Dissection and Grading of Ovarian Development in Wild-Type Female Insects.

Migratory insect pests pose serious challenges to food production and security all over the world. The migratory pests can be monitored and captured using searchlight traps. One of the most important techniques for migratory pest forecasting is to identify the migratory species. However, in most cases, it is difficult to get the information just by appearance. Therefore, using knowledge acquired by systematic analysis of the female reproductive system can help to understand the combined anatomic morphology of the ovarian mating sac and ovary developmental grading of wild-type migratory insects captured with searchlight traps. To demonstrate the applicability of this method, ovarian development status and egg grain development stages were directly assessed in Helicoverpa armigera, Mythimna separata, Spodoptera litura, and Spodoptera exigua for the ovarian anatomy, and the ovarian mating sacs were studied in Agrotis ipsilon, Spaelotis valida, Helicoverpa armigera, Athetis lepigone, Mythimna separata, Spodoptera litura, Mamestra brassicae, and Spodoptera exigua, to explore their relationships. This work shows the specific dissection method to predict wild-type migratory insects, comparing the unique reproductive system of different migratory insects. Then, both tissues, namely, the ovary and mating sacs, were further investigated. This method helps to predict the dynamics and the structural development of reproductive systems in wild-type female migratory insects.

Nutrient supply and accessibility in plants: effect of protein and carbohydrates on Australian plague locust (Chortoicetes terminifera) preference and performance.

In contrast to predictions from nitrogen limitation theory, recent studies have shown that herbivorous migratory insects tend to be carbohydrate (not protein) limited, likely due to increased energy demands, leading them to preferentially feed on high carbohydrate plants. However, additional factors such as mechanical and chemical defenses can also influence host plant choice and nutrient accessibility. In this study, we investigated the effects of plant protein and carbohydrate availability on plant selection and performance for a migratory generalist herbivore, the Australian plague locust, Chortoicetes terminifera. We manipulated the protein and carbohydrate content of seedling wheat (Triticum aestivum L.) by increasing the protein:carbohydrate ratio using nitrogen (N) fertilizer, and manipulated the physical structure of the plants by grinding and breaking down cell walls after drying the plants. Using a full factorial design, we ran both choice and no-choice experiments to measure preference and performance. We confirmed locust preference for plants with a lower protein-carbohydrate ratio (unfertilized plants). Unlike previous studies with mature wild grass species, we found that intact plants supported better performance than dried and ground plants, suggesting that cell wall removal may only improve performance for tougher or more carbohydrate-rich plants. These results add to the growing body of evidence suggesting that several migratory herbivorous species perform better on plants with a lower protein:carbohydrate ratio.

Probing Transcriptional Crosstalk between Cryptochromes and Iron-sulfur Cluster Assembly 1 (MagR) in the Magnetoresponse of a Migratory Insect.

Many organisms can sense and respond to magnetic fields (MFs), with migratory species in particular utilizing geomagnetic field information for long-distance migration. Cryptochrome proteins (Crys) along with a highly conserved Iron-sulfur cluster assembly protein (i.e., MagR) have garnered significant attention for their involvement in magnetoresponse (including magnetoreception). However, in vivo investigations of potential transcriptional crosstalk between Crys and MagR genes have been limited. The brown planthopper, Nilaparvata lugens, is a major migratory pest insect and an emerging model for studying MF intensity-related magnetoresponse. Here, we explored in vivo transcriptional crosstalk between Crys (Cry1 and Cry2) and MagR in N. lugens. The expression of Crys and MagR were found to be sensitive to MF intensity changes as small as several micro-teslas. Knocking down MagR expression led to a significant downregulation of Cry1, but not Cry2. The knockdown of either Cry1 or Cry2 individually did not significantly affect MagR expression. However, their double knockdown resulted in significant upregulation of MagR. Our findings clearly indicate transcriptional crosstalk between MagR and Crys known to be involved in magnetoresponse. This work advances the understanding of magnetoresponse signaling and represents a key initial step towards elucidating the functional consequences of these novel in vivo interactions.

Possible source and migration pathway for early-summer immigrants of the oriental armyworm, Mythimna separata, arriving in northern Japan

The first generation of the oriental armyworm, Mythimna separata (Walker), arrives every year in northern Japan in mainly late May to early June. Analyses of weather maps suggested that this moth's immigration source could be eastern China, but the accuracy of those analyses was very limited due to the lack of a current standard trajectory analysis. The management of migratory insect pests such as M. separata benefits from the identification of the migration source(s) and pathway(s) of the pests. The present study provides a trajectory analysis for M. separata. Backward trajectories from trap sites in northern Japan were calculated with the HYSPLIT System developed by the U.S. National Oceanic and Atmospheric Administration, taking the flight speed of M. separata and the limitation of low ambient temperature at flight height into account. The ending times of the moth's short and long trajectories were set at dusk on the day before and two days before the possible arrival date, respectively. The results suggested two types of possible migration pathway: a multi-step pathway from Northeast China, the Korean Peninsula, and eastern Russia, which are destination areas of the first-generation's migration, and a direct pathway from seasonal main emigration areas in eastern China such as Jiangsu and Shandong provinces. These findings contribute to our understanding of the migration ecology of M. separata and can be used for the development of methods to predict the migration of this insect.

Biotic Borders: Transpacific Plant and Insect Migration and the Rise of Anti-Asian Racism in America, 1890–1950 by Jeannie N. Shinozuka (review)

Biotic Borders: Transpacific Plant and Insect Migration and the Rise of Anti-Asian Racism in America, 1890–1950 by Jeannie N. Shinozuka (review)

Biotic Borders: Transpacific Plant and Insect Migration and the Rise of Anti-Asian Racism in America, 1890–1950 by Jeannie Shinozuka

In Biotic Borders, Shinozuka investigates how immigration exclusion affected both race and species during the rise of the U.S. nation-state. Drawing interdisciplinary methods and frameworks primarily from Asian American studies and histories of science, Shinozuka artfully demonstrates how national fears about Asian immigration not only concerned migrant human bodies but also folded nonhuman forms into racial and exclusionary policies. Although “open border” policies prior to the Page Act of 1875 and the Chinese Exclusion Act of 1882 applied to both human and nonhuman migrant species, xenophobia stoked by the rise of Asian immigration constructed new “categories of native- and invasive-defined groups as bio-invasions that must be regulated or somehow annihilated during American empire-building” (11, emphasis added). Thus, the management of species at the U.S. border, as Shinozuka demonstrates, was predicated on the racial logics of exclusion that governed immigration during the late nineteenth and early twentieth centuries. Biotic Borders powerfully expands critiques of the history of U.S. immigration to encapsulate the transpacific movement of nonhuman insect and plant species, revealing how race and species have productively co-constituted one another as categories of social and political difference.In recent years, work in Asian American studies has productively engaged the theoretical and conceptual implications of the entwinement between race and species, such as in the work of Lee, Chen, Huang, and Ahuja, among others.1 More broadly, Asian American studies have always been invested in the dehumanizing rhetoric that casts Asian immigrants as infectious alien invaders, in what is commonly referred to as Yellow Peril discourse.2 More than merely revealing xenophobic rhetoric as dehumanizing, this work underscores the material and historical processes of Asian American racial formation as a political project contingent on U.S. nation-building—the consolidation of the U.S. empire through the degradation of Asian bodies at its borders. Within this genealogy of robust intellectual inquiry, Shinozuka reveals how the imaginaries of entomologists, botanists, and other scientists produced the social and political conditions for the Yellow Peril rhetoric, thus implicating scientific knowledge in the creation of racial meaning.Moving through different moments in entomological and botanical history that cast foreign plants and insects as racialized invaders threatening the biotic ecosystem of the United States, Biotic Borders insists that the regulation of plant and insect immigration was integral to the racial exclusion that contributed to building the U.S. empire. Science, as Bahng argues, is a cultural, not an objective, form of knowledge that “participate[s] in the construction of national and international ideas about modernity and futurity.”3 Shinozuka’s careful reading of immigration policy alongside intellectual exchanges between scientists aptly demonstrates the cultural and political force behind the intertwined formations of race and species as nodes of difference. By bringing these histories together, Biotic Borders is an important intervention into ideas about immigration and the function of race and species in nation-building. This book offers urgent contributions to Asian American studies, the history of science, environmental studies, and posthumanism. Its interdisciplinary engagement sheds new light on the histories of race, species, and immigration.

Sulfur stable isotopes as a tracer of insect migration and consumption by fish predators

Resource flows between freshwater ecosystems can greatly affect foodweb dynamics. The seasonal movement of a family of aquatic insects, water boatmen, or corixids (Hemiptera: Corixidae) represents an important transfer of resources between wetland and river ecosystems. Corixids migrate en masse from wetlands in the North American prairies to rivers every autumn to overwinter. In the North and South Saskatchewan rivers, Saskatchewan, Canada, several fish species prey upon these migratory corixids. Here, we examined the utility of the stable isotope ratio of sulfur, δ34S, in tracing the migration of corixids between wetlands and the North and South Saskatchewan rivers. We also assessed the extent to which riverine fish use migratory corixids as a dietary subsidy. We found that both corixids and other wetland invertebrates exhibited a mean δ34S value of −10.5 ± 5.8‰, lower than riverine invertebrates at −4.1 ± 4.1‰. Specifically, riverine invertebrates from the South Saskatchewan River were more depleted in 34S than those from the North Saskatchewan River, with means of −5.1 ± 4.1‰ and −1.4 ± 2.8‰, respectively. In summer, corixid-feeing and noncorixid-feeding fish exhibited similar δ34S values in liver tissue, whereas in spring and autumn, corixid feeders exhibited more negative δ34S values. Isotope mixing models indicated that corixid-feeding species may have derived 34 to 65% of liver tissue from wetland sources in spring, 15 to 34% in summer, and 41 to 78% in autumn, whereas contributions to noncorixid-feeding species ranged from 4 to 17% across all seasons. We conclude that δ34S has the potential to trace insect movement and consumer use between isotopically distinct freshwater systems.

The dispersal patterns of a migratory insect are driven by biotic interactions

AbstractAimThe distribution of a species in an area depends on the presence of suitable climatic conditions, suitable biotic interactions and species dispersal capabilities. Studies of species migration usually do not include all these factors due to a lack of detailed ecological information or appropriate methods. Here, we present simulations that consider all those factors for the study of the migratory patterns of Urania boisduvalii by incorporating environmental suitability, biotic interactions with its host plants (Omphalea spp.), and the moth dispersal capacity.LocationCuba.TaxonUrania and Omphalea.MethodsOur approach considers changes in the palatability of plants resulting from foraging by moths, as the novel mechanism driving their dispersal. Here, the state of each cell is determined by climate, dispersal, presence of edible food plants and change in food plant palatability.ResultsUrania dispersal occurs among sites with both edible food plants and suitable climates within the dispersal capacity of the moths. The number of isolated clusters of suitable patches decreased with larger dispersal capacities. All simulations where the palatability recovery is faster than palatability loss, lead to an oscillatory pattern of a local nature, while the other ones lead to a steady occupancy or extirpation of the moth species.Main ConclusionsOur results provide theoretical support for the hypothesis that the palatability of food plants drives the pattern of movement of the moths and predict that the relationship between toxic and non‐toxic periods is critical to determining steady occupancy, oscillatory occupancy or extirpation of the moth from the host plant patches. The conceptual framework we used is directly based on classic literature and the methods we used are implemented as an R package. Therefore, our approach is suited to model, in a practical way, invasive species, emerging diseases or migratory species.

Host-Plant Switching Impacts Susceptibility and Biochemical Responses of Cnaphalocrocis medinalis to Abamectin and Chlorpyrifos

Insect tolerance to insecticides is closely related to the host plant. Migratory insects flying downwind and landing randomly may face host-plant switching after migration. However, it is not clear whether host-plant switching affects the tolerance of migratory insects to insecticides. In the present work, Cnaphalocrocis medinalis, a migratory pest destructive to rice, was studied to explore this issue. The results show that the host-plant switch reduced the susceptibility of rice and wheat larvae populations to abamectin but increased that of wheat larvae populations to chlorpyrifos, indicating that host switching resulted in different tolerance to different insecticides. Enzyme activity determination showed that, although abamectin and chlorpyrifos affect the activities of detoxification enzymes (carboxylesterase, multifunctional oxidase, and glutathione S-transferases), antioxidant enzymes (superoxide dismutase, peroxidase, and catalase), and acetylcholinesterase at sublethal dosages, the effect depends on the host plant and insecticide species. Overall, our findings show that the induction of C. medinalis by host switching affects its susceptibility and biochemical responses to abamectin and chlorpyrifos. Insecticides against C. medinalis should be used with consideration of the potential impact of host switching. Reasonable selection and usages of insecticides can help in the resistance management and control of migratory insects.

New insights into the genetic structure of the outbreak-prone bamboo grasshoppers

IntroductionThe genetic structure of species is shaped by natural (e.g., terrain, climate) and non-natural (e.g., human activities) factors. Geographical isolation and natural barriers are important causes of genetic structure formation of species. Here, we explored this issue in bamboo grasshopper, Ceracris kiangsu, which is an important pest that feeds on bamboo in East and Southeastern Asia.MethodsBased on 186 newly sequenced and 286 previously sequenced mitochondrial COI fragments, and 8 nuclear microsatellite loci, we examined the genetic diversity and population genetic structure of C. kiangsu.ResultsThe degree of genetic differentiation among populations was also high, and Mantel test showed that it was significantly correlated with geographical distance. Principal coordinate analysis and STRUCTURE results revealed two genetically different groups, a South China (S-China) Group and a Southeast Asia (SE-Asia) Group. Climate variables partly explained the population genetic structure. The demographic history and ABC showed that the S-China Group experienced population expansion, whereas the SE-Asia Group was consistently stable.DiscussionOur study demonstrates an obvious population structure maintained in this migratory insect and reveals the potential effect of past climatic change, geographical isolation, and ecological factors on the evolution of their genetic structure.

Effect of Distance from Wetland Borders on Hymenopteran Wasps and Spider Abundance in Maize-soybean Cropping System

The non-crop habitats within agroecosystems are important resources for ecological and biological insect pest management. Diversified cropping systems are known to influence pests populations, however, how neighboring habitats to the agricultural fields affect insect pest natural enemies population dynamics is not clear. This study focused on understanding the influence of wetland borders on Hymenoptera wasps and predatory spider prevalence in a maize-soybean intercrop system. The Hymenoptera wasps and spiders population estimates were carried out in twelve farmers’ fields stratified within 0-300 and 500-1100 meters from the wetland borders. Data were collected once a week starting one week from the emergence of maize and soybean plants until post-flower growth of the two crops. Results showed crop fields within 0-300 meters from the wetland borders had significantly higher numbers of wasps and spiders, while crop fields set up at 500-1100 meters from the wetland borders, the population of Hymenoptera wasps and spiders was significantly reduced. The findings of this study indicate that stable habitats such as wetland borders harbour higher numbers of natural enemies of crop pests and crop fields at close proximity benefit from quick migration of natural enemies from the pool in stable habitats. These findings can be used to design field architectures such as field margins or borders that can support insect pest natural enemies survival and migration into crop fields.

Wind-assisted high-altitude dispersal of mosquitoes and other insects in East Africa.

Knowledge of insect dispersal is relevant to the control of agricultural pests, vector-borne transmission of human and veterinary pathogens, and insect biodiversity. Previous studies in a malaria endemic area of the Sahel region in West Africa revealed high-altitude, long-distance migration of insects and various mosquito species. The objective of the current study was to assess whether similar behavior is exhibited by mosquitoes and other insects around the Lake Victoria basin region of Kenya in East Africa. Insects were sampled monthly from dusk to dawn over 1 year using sticky nets suspended on a tethered helium-filled balloon. A total of 17,883 insects were caught on nets tethered at 90, 120, and 160 m above ground level; 818 insects were caught in control nets. Small insects (<0.5 cm, n = 15,250) were predominant regardless of height compared with large insects (>0.5 cm, n = 2,334) and mosquitoes (n = 299). Seven orders were identified; dipteran was the most common. Barcoding molecular assays of 184 mosquitoes identified 7 genera, with Culex being the most common (65.8%) and Anopheles being the least common (5.4%). The survival rate of mosquitoes, experimentally exposed to high-altitude overnight, was significantly lower than controls maintained in the laboratory (19% vs. 85%). There were no significant differences in mosquito survival and oviposition rate according to capture height. These data suggest that windborne dispersal activity of mosquito vectors of malaria and other diseases occurs on a broad scale in sub-Saharan Africa.

Pollen Molecular Identification from a Long-Distance Migratory Insect, Spodoptera exigua, as Evidenced for Its Regional Pollination in Eastern Asia.

Understanding plant-insect interactions requires the uncovering of the host plant use of insect herbivores, but such information is scarce for most taxa, including nocturnal moth species, despite their vital role as herbivores and pollinators. In this study, we determined the plant species visited by an important moth species, Spodoptera exigua, by analyzing attached pollen on migratory individuals in Northeast China. Pollen grains were dislodged from 2334 S. exigua long-distance migrants captured between 2019 and 2021 on a small island in the center of the Bohai Strait, which serves as a seasonal migration pathway for this pest species, and 16.1% of the tested moths exhibited pollen contamination, primarily on the proboscis. Subsequently, 33 taxa from at least 23 plant families and 29 genera were identified using a combination of DNA barcoding and pollen morphology, primarily from the Angiosperm, Dicotyledoneae. Moreover, the sex, inter-annual, and seasonal differences in pollen adherence ratio and pollen taxa were revealed. Notably, compared to previously reported pollen types found on several other nocturnal moths, we found that almost all of the above 33 pollen taxa can be found in multiple nocturnal moth species, providing another important example of conspecific attraction. Additionally, we also discussed the indicative significance of the pollen present on the bodies of migratory individuals for determining their migratory route. Overall, by delineating the adult feeding and pollination behavior of S. exigua, we advanced our understanding of the interactions of the moths with their host plants, and its migration pattern, as well as facilitated the design of (area-wide) management strategies to preserve and optimize ecosystem services that they provide.

A geometric morphometrics and genetics characterization of Vanessa carye in an extreme elevational gradient in the Chilean Altiplano

The Western Painted Lady butterfly, Vanessa carye (Hüber, 1812), in addition to pre-senting an extensive distribution in South America, has been observed flying in the Chilean Alti-plano from the coast to the highlands, from 0 to 5200 m.a.s.l. and it is suggested that could be a migratory insect. Some animal species move from one place to another by migration searching for favorable conditions. Wings of flying migratory animals are the principal trait involved in move-ment, and their shape has been documented to change between migratory and non-migratory species or populations. In this sense, little is known about the adaptations of butterflies to elevational gradients, so the V. carye's wide latitudinal and altitudinal range coupled with the different climatic conditions makes this species an interesting subject for adaptation studies. This research studies V. carye at different elevational ranges in extreme environments at the Chilean Altiplano and Atacama Desert to determine the presence of morphotypes through geometric morphometrics associated with altitudinal patterns, and to determine the genetic diversity and population structure of this species by using COI molecular marker. Subtle morphometric changes between populations were found, so two morphometric lineages were defined: a “coastal” lineage with more elongated wings and an “altiplano” lineage with more rounded wings. Nevertheless, low genetic diversity and no genetic structure associated to these morphological differences were found. Understanding the processes underlying the wing shape of V. carye morphological adaptations will help to understand its natural history. Results here may be a first approach of evidence to answer the question “Is this butterfly a migratory species?”

The Afrotropical breeding grounds of the Palearctic-African migratory painted lady butterflies (Vanessa cardui)

Migratory insects are key players in ecosystem functioning and services, but their spatiotemporal distributions are typically poorly known. Ecological niche modeling (ENM) may be used to predict species seasonal distributions, but the resulting hypotheses should eventually be validated by field data. The painted lady butterfly (Vanessa cardui) performs multigenerational migrations between Europe and Africa and has become a model species for insect movement ecology. While the annual migration cycle of this species is well understood for Europe and northernmost Africa, it is still unknown where most individuals spend the winter. Through ENM, we previously predicted suitable breeding grounds in the subhumid regions near the tropics between November and February. In this work, we assess the suitability of these predictions through i) extensive field surveys and ii) two-year monitoring in six countries: a large-scale monitoring scheme to study butterfly migration in Africa. We document new breeding locations, year-round phenological information, and hostplant use. Field observations were nearly always predicted with high probability by the previous ENM, and monitoring demonstrated the influence of the precipitation seasonality regime on migratory phenology. Using the updated dataset, we built a refined ENM for the Palearctic-African range of V. cardui. We confirm the relevance of the Afrotropical region and document the missing natural history pieces of the longest migratory cycle described in butterflies.

Quantitative Effects of Temperature and Exposure Duration on the Occurrence and Repair of Indirect Chilling Injury in the Fall Armyworm Spodoptera frugiperda

The fall armyworm (FAW) Spodoptera frugiperda is a long-distance migratory insect pest, and the invaded range of its recent expansion includes regions colder than the tropical and subtropical regions in East Asia. In order to understand the potential distribution of S. frugiperd in temperate and colder regions, we quantified the effects of temperature and exposure duration on the degree of indirect chilling injury caused to S. frugiperd under laboratory conditions. The adults were more tolerant to moderately low temperatures (3 to 15 °C) than the larvae and pupae. Survival decreased significantly when adult S. frugiperd were exposed to temperatures of 9 °C or lower. A time-temperature model suggested that indirect chilling injury began occurring at 15 °C. Survival was improved by short-term daily exposure to higher temperatures, indicating the existence of a repair mechanism for indirect chilling injury in S. frugiperd. The degree of repair depended on the temperature, but the relationship was not a simple direct proportion. These findings on indirect chilling injury and repair will improve the estimation of the potential distribution of S. frugiperd in temperate and colder regions.

Transcriptomic analysis of Mythimna separata ovaries and identification of genes involved in reproduction

The migratory insect Mythimna separata is a major pest of grain crops in Asia. Unfortunately, the molecular mechanisms that control and regulate reproduction in this species remain unclear. In this study, transcriptome sequencing was utilized to identify genes associated with ovary development and oogenesis. Clean sequences totaling 117.71 Gb were assembled into 178,534 unigenes with a mean length of 647.37 bp and N50 length of 837 bp. Transcriptome analysis showed that 7921 unigenes were significantly expressed in ovaries with 4403 and 3518 unigenes up- and down-regulated, respectively. Enrichment analysis with the Kyoto Encyclopedia of Genes and Genomes database suggested that 729 differentially expressed genes were significantly enriched in the top 20 pathways (q-values <0.05). Twenty genes were associated with ovary development and oogenesis and included lipases, Nanos, small heat shock proteins (sHsps) and histones; these were further verified by qRT-PCR and may play essential roles in M. separata reproduction. Collectively, our findings reveal underlying mechanisms of M.separata reproduction and may lead to RNAi-based management strategies targeting reproductive physiology.

Effect of rearing conditions on fatty acid allocation during flight in nectivorous lepidopteran Mythimna unipuncta

Insect species that are nectivorous as adults acquire essential fatty acids almost exclusively from host plants during larval development. Thus, as essential fatty acids are important for a number of different biological processes, adult allocation of this limited resource may result in important trade-offs. Most lepidopteran species that migrate do so as sexually immature adults, so essential fatty acids used for migratory flight would not be available for subsequent reproduction. Using the true armyworm, Mythimna unipuncta, as a model system we analyzed fat body samples to test the hypothesis that environmental cues would influence the use of essential fatty acids during migratory flight. We used diets manipulated isotopically to trace origins and use of stored lipids and used chromatographic analyses to determine fatty acid composition. In the first experiments, 5-day old moths that had been reared in summer or fall (migratory) conditions and were force flown for different lengths of time (0–6 h) after which samples of the fat body were analyzed. Rearing conditions did not affect fatty acid loading however patterns of use during flight differed with essential fatty acids being conserved under fall but not summer conditions. As migratory flight can take several days, we repeated the experiment when 5-day old moths were flown for 8 h each day for up to 5 days. Some moths were provided access to sugar water after each flight while others were only given water or only given sugar water once. When sugar water was readily or sporadically available, moths reared under fall conditions conserved their essential fatty acids indicating that the environmental cues responsible for the onset of migratory flight result in physiological changes that modify lipid use. However, when moths had only water, the essential fatty acids were not conserved, highlighting the importance of nectar availability at stopovers for the conservation essential fatty acids during migration. Isotopic analysis of the moth fat body indicated a large contribution of adult-derived diet to lipids used as fuel. The implications of using isotopic approaches to other flight studies and future research on differential resource allocation in winged monomorphic migratory insects are discussed. Summary statement: Isotopic tracing methods and gas chromatography were used to demonstrate that environmental cues can impact patterns of fatty acid use in true armyworm moths. In particular, essential fatty acids are conserved during migratory flight. However, availability of adult food sources will determine the degree to which essential fatty acids are conserved.

Biological Characteristics and Energy Metabolism of Migrating Insects.

Through long-distance migration, insects not only find suitable breeding locations and increase the survival space and opportunities for the population but also facilitate large-scale material, energy, and information flow between regions, which is important in maintaining the stability of agricultural ecosystems and wider natural ecosystems. In this study, we summarize the changes in biological characteristics such as morphology, ovarian development, reproduction, and flight capability during the seasonal migration of the insect. In consideration of global research work, the interaction between flight and reproduction, the influence and regulation of the insulin-like and juvenile hormone on the flight and reproductive activities of migrating insects, and the types of energy substances, metabolic processes, and hormone regulation processes during insect flight are elaborated. This systematic review of the latest advances in the studies on insect migration biology and energy metabolism will help readers to better understand the biological behavior and regulation mechanism of the energy metabolism of insect migration.