Comparative flight performance of three important pest Adelphocoris species of Bt cotton in China

Pest Status, Bio-Ecology, and Area-Wide Management of Mirids in East Asia

Mirids (Hemiptera: Heteroptera: Miridae) feed upon a wide variety of cultivated and wild plants and can be economically important crop pests. They have traditionally been perceived as innocuous herbivores in East Asia; however, population levels of various mirid species have dramatically increased over the past decades. High-profile pests such as Apolygus spp., Adelphocoris spp., and Lygus spp. are now widely distributed across the region, and their infestation pressure is associated with climate, agroecological conditions, and farming practices. This review outlines how an in-depth understanding of pest biology, a systems-level characterization of pest ecology, and a comprehensive evaluation of integrated pest management tactics have enabled sustainable management of mirids across crop boundaries and harvest cycles. This work underscores how more holistic, integrative research approaches can accelerate the implementation of area-wide management of generalist pests, effectively prevent pest population build-up and yield impact, and shrink the environmental footprint of agriculture. In addition to highlighting the merits of interdisciplinary systems approaches, we discuss prospects and challenges for the sustainable management of polyphagous mirid pests in landscape matrices.

Thermal and Oxygen Flight Sensitivity in Ageing Drosophila melanogaster Flies: Links to Rapamycin-Induced Cell Size Changes

Simple Summary

Cold-blooded organisms can become physiologically challenged when performing highly oxygen-demanding activities (e.g., flight) across different thermal and oxygen environmental conditions. We explored whether this challenge decreases if an organism is built of smaller cells. This is because small cells create a large cell surface, which is costly, but can ease the delivery of oxygen to cells’ power plants, called mitochondria. We developed fruit flies in either standard food or food with rapamycin (a human drug altering the cell cycle and ageing), which produced flies with either large cells (no supplementation) or small cells (rapamycin supplementation). We measured the maximum speed at which flies were flapping their wings in warm and hot conditions, combined with either normal or reduced air oxygen concentrations. Flight intensity increased with temperature, and it was reduced by poor oxygen conditions, indicating limitations of flying insects by oxygen supply. Nevertheless, flies with small cells showed lower limitations, only slowing down their wing flapping in low oxygen in the hot environment. Our study suggests that small cells in a body can help cold-blooded organisms maintain demanding activities (e.g., flight), even in poor oxygen conditions, but this advantage can depend on body temperature.

Abstract

Ectotherms can become physiologically challenged when performing oxygen-demanding activities (e.g., flight) across differing environmental conditions, specifically temperature and oxygen levels. Achieving a balance between oxygen supply and demand can also depend on the cellular composition of organs, which either evolves or changes plastically in nature; however, this hypothesis has rarely been examined, especially in tracheated flying insects. The relatively large cell membrane area of small cells should increase the rates of oxygen and nutrient fluxes in cells; however, it does also increase the costs of cell membrane maintenance. To address the effects of cell size on flying insects, we measured the wing-beat frequency in two cell-size phenotypes of Drosophila melanogaster when flies were exposed to two temperatures (warm/hot) combined with two oxygen conditions (normoxia/hypoxia). The cell-size phenotypes were induced by rearing 15 isolines on either standard food (large cells) or rapamycin-enriched food (small cells). Rapamycin supplementation (downregulation of TOR activity) produced smaller flies with smaller wing epidermal cells. Flies generally flapped their wings at a slower rate in cooler (warm treatment) and less-oxygenated (hypoxia) conditions, but the small-cell-phenotype flies were less prone to oxygen limitation than the large-cell-phenotype flies and did not respond to the different oxygen conditions under the warm treatment. We suggest that ectotherms with small-cell life strategies can maintain physiologically demanding activities (e.g., flight) when challenged by oxygen-poor conditions, but this advantage may depend on the correspondence among body temperatures, acclimation temperatures and physiological thermal limits.

Effects of Starvation, Age, and Mating Status on Flight Capacity of Laboratory-Reared Brown Marmorated Stink Bug (Hemiptera: Pentatomidae)

The brown marmorated stink bug, Halyomorpha halys (Stål) (Hemiptera: Pentatomidae), is an invasive species to North America and has spread throughout most of the territory. Understanding flight in H. halys is crucial to understanding the dispersal capacity and developing forecasting models for this pest. The purpose of this research was to assess the effects of starvation, age, mating status, sex, and preflight weight on flight parameters of laboratory-reared H. halys using computer-monitored flight mills. The mean flight distance observed over a 24-h period was 266 m and the maximum distance was 7.3 km. Overall, the flight capacity of males and females was similar, even though females weighed more than males. The proportion of H. halys that initiated flight was not affected by starvation, age, or mating status. The number of bouts of individual flights and velocity significantly increased with longer durations of starvation. The number of bouts significantly decreased with increasing age. The total distance flew and total flight time was not affected by starvation, age, or mating status. Although some statistical differences were seen across the experiments, these differences likely represent minimal ecological significance. Therefore, these results suggest that H. halys are remarkably resilient, which may contribute to their success as an invasive species. The findings of this study could help better predict the dispersal potential of H. halys in Minnesota.

Apolygus lucorum genome provides insights into omnivorousness and mesophyll feeding

Apolygus lucorum (Miridae) is an omnivorous pest that occurs worldwide and is notorious for the serious damage it causes to various crops and substantial economic losses. Although some studies have examined the biological characteristics of the mirid bug, no reference genome is available in Miridae, limiting in-depth studies of this pest. Here, we present a chromosome-scale reference genome of A. lucorum, the first sequenced Miridae species. The assembled genome size was 1.02 Gb with a contig N50 of 785 kb. With Hi-C scaffolding, 1,016 Mb contig sequences were clustered, ordered and assembled into 17 large scaffolds with scaffold N50 length 68 Mb, each corresponding to a natural chromosome. Numerous transposable elements occur in this genome and contribute to the large genome size. Expansions of genes associated with omnivorousness and mesophyll feeding such as those related to digestion, chemosensory perception, and detoxification were observed in A. lucorum, suggesting that gene expansion contributed to its strong environmental adaptability and severe harm to crops. We clarified that a salivary enzyme polygalacturonase is unique in mirid bugs and has significantly expanded in A. lucorum, which may contribute to leaf damage from this pest. The reference genome of A. lucorum not only facilitates biological studies of Hemiptera as well as an understanding of the damage mechanism of mesophyll feeding, but also provides a basis on which to develop efficient control technologies for mirid bugs.

Flight Performance of Mamestra brassicae (Lepidoptera: Noctuidae) Under Different Biotic and Abiotic Conditions

Mamestra brassicae L. is an important, regionally migratory pest of vegetable crops in Europe and Asia. Its migratory activity contributes significantly to population outbreaks, causing severe crop yield losses. Because an in-depth understanding of flight performance is key to revealing migratory patterns, here we used a computer-linked flight mill and stroboscope to study the flight ability and wingbeat frequency (WBF) of M. brassicae in relation to sex, age, temperature, and relative humidity (RH). The results showed that age significantly affected the flight ability and WBF of M. brassicae, and 3-d-old individuals performed the strongest performance (total flight distance: 45.6 ± 2.5 km; total flight duration: 9.3 ± 0.3 h; WBF: 44.0 ± 0.5 Hz at 24°C and 75% RH). The age for optimal flight was considered to be 2-3 d old. Temperature and RH also significantly affected flight ability and WBF; flight was optimal from 23°C to 25°C and 64-75% RH. Because M. brassicae thus has great potential to undertake long-distance migration, better knowledge of its flight behavior and migration will help establish a pest forecasting and early-warning system.

Host-plant switching promotes the population growth of Apolygus lucorum: implications for laboratory rearing

The mirid bug Apolygus lucorum (Meyer-Dür) (Hemiptera: Miridae) is a major pest on cotton, fruit trees and other crops in China. A. lucorum adults often switch host plants in the agro-ecosystem, and such host-plant switching may promote more rapid population growth of A. lucorum. Here, we examined the population fitness of A. lucorum on different combinations of two plant foods [fresh maize kernels (Zea mays) and green bean pods (Phaseolus vulgaris)] in the laboratory when reared either individually or in groups. Our results suggested that, compared with A. lucorum nymphs reared on green bean alone, the survival rate, developmental rate, and adult weight significantly increased when they were fed fresh maize kernels for both rearing methods. Both two-plant combinations of foods (i.e., maize as nymphal food then green bean as adult food, and green bean as nymphal food then maize as adult food) generally prolonged adult longevity, improved female fecundity, and higher egg hatching rate compared with maize or green bean as food for both nymphs and adults. The combination of nymphs with maize and adults with green bean showed the highest population growth rate for both individual and group rearing of mirid bugs. Host food switching greatly promoted the population growth of A. lucorum, and suggests a new diet for laboratory rearing of A. lucorum.

The tethered flight technique as a tool for studying life-history strategies associated with migration in insects

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 50 years, 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.

Onset of Oviposition Triggers Abrupt Reduction in Migratory Flight Behavior and Flight Muscle in the Female Beet Webworm, Loxostege sticticalis

Flight and reproduction are usually considered as two life history traits that compete for resources in a migratory insect. The beet webworm, Loxostege sticticalis L., manages the costs of migratory flight and reproduction through a trade-off in timing of these two life history traits, where migratory behavior occurs during the preoviposition period. To gain insight into how migratory flight and reproduction are coordinated in the female beet webworm, we conducted experiments beginning at the end of the preoviposition period. We used flight mills to test whether flight performance and supportive flight musculature and fuel are affected by the number of eggs oviposited, or by the age of mated and unmated females after onset of oviposition by the former. The results showed that flight distance, flight velocity, flight duration, and flight muscle mass decreased abruptly at the onset of oviposition, compared to that of virgin females of the same age which did not change over the next 7 d. These results indicate that onset of oviposition triggers a decrease in flight performance and capacity in female beet webworms, as a way of actively managing reallocation of resources away from migratory flight and into egg production. In addition to the abrupt switch, there was a gradual, linear decline in flight performance, flight muscle mass, and flight fuel relative to the number of eggs oviposited. The histolysis of flight muscle and decrease of triglyceride content indicate a progressive degradation in the ability of adults to perform additional migratory flights after onset of oviposition. Although the results show that substantial, albeit reduced, long-duration flights remain possible after oviposition begins, additional long-distance migratory flights probably are not launched after the initiation of oviposition.

The Mouthparts Enriched Odorant Binding Protein 11 of the Alfalfa Plant Bug Adelphocoris lineolatus Displays a Preferential Binding Behavior to Host Plant Secondary Metabolites

Odorant binding proteins (OBPs) are proposed to be directly required for odorant discrimination and represent potential interesting targets for pest control. In the notoriously agricultural pest Adelphocoris lineolatus, our previous functional investigation of highly expressed antennal OBPs clearly supported this viewpoint, whereas the findings of the current study by characterizing of AlinOBP11 rather indicated that OBP in hemipterous plant bugs might fulfill a different and tantalizing physiological role. The phylogenetic analysis uncovered that AlinOBP11 together with several homologous bug OBP proteins are potential orthologs, implying they could exhibit a conserved function. Next, the results of expression profiles solidly showed that AlinOBP11 was predominantly expressed at adult mouthparts, the most important gustatory organ of Hemiptera mirid bug. Finally, a rigorously selective binding profile was observed in the fluorescence competitive binding assay, in which recombinant AlinOBP11 displayed much stronger binding abilities to non-volatile secondary metabolite compounds than the volatile odorants. These results reflect that AlinOBP11, even its orthologous proteins across bug species, could be associated with a distinctively conserved physiological role such as a crucial carrier for non-volatiles host secondary metabolites in gustatory system.

Odorant-binding and chemosensory proteins identified in the antennal transcriptome of Adelphocoris suturalis Jakovlev

Adelphocoris suturalis Jakovlev (Hemiptera: Miridae) is an insect pest that causes severe agricultural damage to cotton and many other important crops. In insects, olfaction is very important throughout their lifetime. There are two groups of small soluble proteins, named odorant binding proteins (OBPs) and chemosensory proteins (CSPs), which are suggested to participate in the initial biochemical recognition steps of insect olfactory signal transduction. In this study, a total of 16 OBPs (12 classical OBPs and 4 plus-C OBPs) and 8 CSPs, were identified in the antennal transcriptome of A. suturalis. The sex- and tissue-specific profiles of these binding protein genes showed that 13 of the 16 OBP transcripts were highly expressed in the antennae of both sexes, and 4 OBPs (AsutOBP1, 4, 5 and 9) were expressed higher in the male antennae compared to the female antennae. Three CSPs (AsutCSP1, 4 and 5) were expressed specifically in the antennae of both sexes, and AsutCSP1 was expressed higher in the male antennae than in the female antennae. Our findings identify several novel OBP and CSP genes for further investigation of the olfactory system of A. suturalis at the molecular level.

Phylogeographic structure of cotton pest Adelphocoris suturalis (Hemiptera: Miridae): strong subdivision in China inferred from mtDNA and rDNA ITS markers

Phylogeographic patterns of some extant plant and vertebrate species have been well studied; however, they are poorly understood in the majority of insects. The study documents analysis of mitochondrial (COI, CYTB and ND5) and nuclear (5.8S rDNA, ITS2 and 28S rDNA) data from 419 individuals of Adelphocoris suturalis, which is one of the main cotton pests found in the 31 locations in China and Japan involved in the study. Results show that the species is highly differentiated between populations from central China and peripheral China regions. Analysis of molecular variance showed a high level of geographical differentiation at different hierarchical levels. Isolation-by-distance test showed no significant correlation between genetic distance and geographical distance among A. suturalis populations, which suggested gene flow is not restricted by distance. In seven peripheral populations, the high levels of genetic differentiation and the small N_em values implied that geographic barriers were more likely restrict gene flow. Neutrality tests and the Bayesian skyline plot suggested population expansion likely happened during the cooling transition between Last Interglacial and Last Glacial Maximum. All lines of evidence suggest that physical barriers, Pleistocene climatic oscillations and geographical heterogeneity have affected the population structure and distribution of this insect in China.

Characterization of Adelphocoris suturalis (Hemiptera: Miridae) Transcriptome from Different Developmental Stages

Adelphocoris suturalis is one of the most serious pest insects of Bt cotton in China, however its molecular genetics, biochemistry and physiology are poorly understood. We used high throughput sequencing platform to perform de novo transcriptome assembly and gene expression analyses across different developmental stages (eggs, 2^nd and 5^th instar nymphs, female and male adults). We obtained 20 GB of clean data and revealed 88,614 unigenes, including 23,830 clusters and 64,784 singletons. These unigene sequences were annotated and classified by Gene Ontology, Clusters of Orthologous Groups, and Kyoto Encyclopedia of Genes and Genomes databases. A large number of differentially expressed genes were discovered through pairwise comparisons between these developmental stages. Gene expression profiles were dramatically different between life stage transitions, with some of these most differentially expressed genes being associated with sex difference, metabolism and development. Quantitative real-time PCR results confirm deep-sequencing findings based on relative expression levels of nine randomly selected genes. Furthermore, over 791,390 single nucleotide polymorphisms and 2,682 potential simple sequence repeats were identified. Our study provided comprehensive transcriptional gene expression information for A. suturalis that will form the basis to better understanding of development pathways, hormone biosynthesis, sex differences and wing formation in mirid bugs.

Chemosensillum immunolocalization and ligand specificity of chemosensory proteins in the alfalfa plant bug Adelphocoris lineolatus (Goeze)

Insect chemosensory proteins (CSPs) are a family of small soluble proteins. To date, their physiological functions in insect olfaction remain largely controversial in comparison to odorant binding proteins (OBPs). In present study, we reported the antenna specific expression of three CSPs (AlinCSP4-6) from Adelphocoris lineolatus, their distinct chemosensillum distribution as well as ligand binding capability thus providing the evidence for the possible roles that they could play in semiochemical detection of the plant bug A. lineolatus. The results of qRT-PCR and western blot assay clearly showed that all of these three CSPs are highly expressed in the adult antennae, the olfactory organ of insects. Further cellular investigation of their immunolocalization revealed their dynamic protein expression profiles among different types of antennal sensilla. In a fluorescence competitive binding assay, the selective ligand binding was observed for AlinCSP4-6. In ad`dition, a cooperative interaction was observed between two co-expressed CSPs resulting in an increase of the binding affinities by a mixture of AlinCSP5 and AlinCSP6 to terpenoids which do not bind to individual CSPs. These findings in combination with our previous data for AlinCSP1-3 indicate a possible functional differentiation of CSPs in the A. lineolatus olfactory system.

Life table parameters of three Mirid Bug (Adelphocoris) species (Hemiptera: Miridae) under contrasted relative humidity regimes

The genus Adelphocoris (Hemiptera: Miridae) is a group of important insect pests of Bt cotton in China. The three dominant species are A. lineolatus, A. suturalis, and A. fasciaticollis, and these species have different population dynamics. The causal factors for the differences in population dynamics have not been determined; one hypothesis is that humidity may be important for the growth of Adelphocoris populations. In the laboratory, the demographic parameters of the three Adelphocoris species were compared when the mirid bugs were subjected to various levels of relative humidity (40, 50, 60, 70 and 80% RH). Middle to high levels of RH (60, 70 and 80%) were associated with higher egg and nymph survival rates and increased adult longevity and female fecundity. Lower humidity levels (40 and 50% RH) had negative effects on the survival of nymphs, adult longevity and fecundity. The intrinsic rate of increase (rm), the net reproductive rate (R0) and the finite rate of increase (λ) for each Adelphocoris species increased with increasing RH. Significant positive relationships were found between RH and the life table parameters, rm, R0 and λ for the three Adelphocoris species. These results will help to better understand the phenology of the three Adelphocoris species, and the information can be used in population growth models to optimize pest forecasting and management strategies for these key pests.

The antenna-specific odorant-binding protein AlinOBP13 of the alfalfa plant bug Adelphocoris lineolatus is expressed specifically in basiconic sensilla and has high binding affinity to terpenoids

Odorant-binding proteins (OBPs) are crucial in the olfactory pathway of insects. In the present study, the antenna-enriched OBP AlinOBP13 was investigated because of its potential contribution to the peripheral olfactory perception in the alfalfa plant bug Adelphocoris lineolatus. The results of quantitative reverse transcriptase-PCR showed that the transcript level of AlinOBP13 was higher in the adult stage than in the nymph stages. The transcript levels of AlinOBP13 in the male and female antennae significantly increased after 4 and 8 h of starvation, respectively. Fine ultrastructures of different types of chemosensilla in both female and male antennae were investigated using transmission electron microscopy and immunocytochemical labelling. The results revealed that the anti-AlinOBP13 antiserum strongly and specifically labelled short basiconic sensilla; this antiserum was restricted to the inner lumen and the cavities below the sensillum base of the sensilla. By contrast, multiporous sensilla trichodea, medium long sensilla basiconica, and aporous sensilla chaetica were not labelled. The present study is the first to report an OBP showing specific expression in the short basiconic sensilla of a member of the Hemipteran species. The results of a fluorescence displacement binding assay indicated that recombinant AlinOBP13 showed a more specific binding preference to terpenoids than to sex pheromones and other classes of chemicals. This binding ability was dramatically affected by pH; higher binding affinities were displayed at pH 10.0 than at pH 7.4 and 5.0. In addition, the results of dose-dependent electroantennogram recordings from the antennae showed that both female and male adult bugs responded to the terpenoids tested, suggesting an apparent physiological relevance of AlinOBP13 in A. lineolatus chemoreception. The results of this study suggest that AlinOBP13 functions as a specific carrier of terpenoids and provide insights into the mechanism of A. lineolatus in response to green volatiles.

Plant volatile analogues strengthen attractiveness to insect

Green leaf bug Apolygus lucorum (Meyer-Dür) is one of the major pests in agriculture. Management of A. lucorum was largely achieved by using pesticides. However, the increasing population of A. lucorum since growing Bt cotton widely and the increased awareness of ecoenvironment and agricultural product safety makes their population-control very challenging. Therefore this study was conducted to explore a novel ecological approach, synthetic plant volatile analogues, to manage the pest. Here, plant volatile analogues were first designed and synthesized by combining the bioactive components of β-ionone and benzaldehyde. The stabilities of β-ionone, benzaldehyde and analogue 3 g were tested. The electroantennogram (EAG) responses of A. lucorum adult antennae to the analogues were recorded. And the behavior assay and filed experiment were also conducted. In this study, thirteen analogues were acquired. The analogue 3 g was demonstrated to be more stable than β-ionone and benzaldehyde in the environment. Many of the analogues elicited EAG responses, and the EAG response values to 3 g remained unchanged during seven-day period. 3 g was also demonstrated to be attractive to A. lucorum adults in the laboratory behavior experiment and in the field. Its attractiveness persisted longer than β-ionone and benzaldehyde. This indicated that 3 g can strengthen attractiveness to insect and has potential as an attractant. Our results suggest that synthetic plant volatile analogues can strengthen attractiveness to insect. This is the first published study about synthetic plant volatile analogues that have the potential to be used in pest control. Our results will support a new ecological approach to pest control and it will be helpful to ecoenvironment and agricultural product safety.

The preferential binding of a sensory organ specific odorant binding protein of the alfalfa plant bug Adelphocoris lineolatus AlinOBP10 to biologically active host plant volatiles

Semiochemicals such as sex pheromones and plant volatiles are crucial components of insect mating systems and host plant localization. In the olfactory signal transduction pathway, odorant-binding proteins (OBPs) are important elements that function in the first step of the pathway by carrying hydrophobic semiochemicals across the sensillum lymph to the olfactory receptors (ORs). In this study, we examined the binding affinities of semiochemicals to AlinOBP10, a putative OBP from the alfalfa plant bug, Adelphocoris lineolatus, that we demonstrate is expressed mainly in sensory organs. We then characterized the biological activities of the high affinity semiochemicals by measuring their electrophysiological activities in antennae and behavioral responses in the plant bug. AlinOBP10 displayed weak binding affinities to two major putative pheromone components, hexyl butyrate and (E)-2-hexenyl butyrate. In contrast, AlinOBP10 exhibited higher binding affinities to six host plant volatiles, namely myrcene, β-pinene, β-ionone, 3-hexanone, (E)-2-hexenal, and 1-hexanol. The biological activities of these six putative ligands were further studied in electroantennogram recordings and Y-tube olfactometer trials. The three compounds, (E)-2-hexenal, 1-hexanol, and 3-hexanone elicited strong electrophysiological responses, but elicited distinct behaviors. While 3-hexanone was attractive to female adults, (E)-2-hexenal and 1-hexanol were significant repellents. Although a weak electrophysiological response was elicited with β-pinene, it was a strong repellent. These results demonstrate that AlinOBP10 can interact with attractants, as well as repellents, with some specificity toward plant volatiles over sex pheromones.

Influence of age, mating status, sex, quantity of food, and long-term food deprivation on red flour beetle (Coleoptera: Tenebrionidae) flight initiation

Effects of age, sex, presence or absence of food, mating status, quantity of food, and food deprivation on rate of and time of flight initiation of the red flour beetle, Tribolium castaneum (Herbst), were determined. Flight initiation declined with increasing age in both presence and absence of food. However, flight initiation was lower when food was present in the flight chambers than in the absence of food. In the presence of food, both mated and virgin beetles were equally likely to disperse by flight. However, in the absence of food, mated beetles initiated flight more readily that virgin individuals. Flight initiation was greatest when little or no food was present. The presence of varying quantities of food inside the flight chambers impacted the number of progeny produced by females before flight, but not the timing of flight. Rate of flight initiation was higher for beetles deprived of food for short periods of time compared with flight initiation of beetles with food in the flight chamber. Flight initiation decreased with increasing time without food. There were no differences in flight tendencies between males and females in the experiments reported here. Our results suggest that T. castaneum uses flight as a mechanism to disperse to new environments during almost any part of their life span and that this type of dispersion does not fit with the model of the so-called true migratory species that involves an "oogenesis-flight syndrome.

Flight mill performance of the lacewing Chrysoperla sinica (Neuroptera: Chrysopidae) as a function of age, temperature, and relative humidity

The lacewing Chrysoperla sinica (Tjeder) (Neuroptera: Chrysopidae) is an important predator of several insect pests in China and has considerable potential as a biological control agent. An inoculative approach would be the releasing adults early in the season to ensure that populations are present before pest densities increase. However, an understanding of adult flight activity under different conditions is necessary to develop appropriate release strategies. Therefore, we used a 32-channel, computer-monitored flight mill system to determine the effect of age on the flight activity of unmated female and male adults. Both sexes had high total flight activity levels as well as the longest individual flight bouts 2 and 3 d after emergence. The effects of temperature (between 13 and 33 degrees C at 75% RH) and relative humidity (between 30 and 90% RH at 23 degrees C) on the flight activity of 3-d-old unmated adults also were determined. Flight activity declined at the lowest (13 degrees C) and highest (33 degrees C) temperatures tested, as well as at the lowest relative humidity (30% RH). These findings are discussed within the context of selecting the appropriate environmental conditions for releasing C. sinica.