Flight Capacity Research Articles

Flight-induced changes in gene expression in the Glanville fritillary butterfly.

Insect flight is one of the most energetically demanding activities in the animal kingdom, yet for many insects flight is necessary for reproduction and foraging. Moreover, dispersal by flight is essential for the viability of species living in fragmented landscapes. Here, working on the Glanville fritillary butterfly (Melitaea cinxia), we use transcriptome sequencing to investigate gene expression changes caused by 15min of flight in two contrasting populations and the two sexes. Male butterflies and individuals from a large metapopulation had significantly higher peak flight metabolic rate (FMR) than female butterflies and those from a small inbred population. In the pooled data, FMR was significantly positively correlated with genome-wide heterozygosity, a surrogate of individual inbreeding. The flight experiment changed the expression level of 1513 genes, including genes related to major energy metabolism pathways, ribosome biogenesis and RNA processing, and stress and immune responses. Males and butterflies from the population with high FMR had higher basal expression of genes related to energy metabolism, whereas females and butterflies from the small population with low FMR had higherexpression of genes related to ribosome/RNA processing and immune response. Following the flight treatment, genes related to energy metabolism were generally down-regulated, while genes related to ribosome/RNA processing and immune response were up-regulated. These results suggest that common molecular mechanisms respond to flight and can influence differences in flight metabolic capacity between populations and sexes.

Bumblebee flight performance in cluttered environments: effects of obstacle orientation, body size and acceleration.

Locomotion through structurally complex environments is fundamental to the life history of most flying animals, and the costs associated with movement through clutter have important consequences for the ecology and evolution of volant taxa. However, few studies have directly investigated how flying animals navigate through cluttered environments, or examined which aspects of flight performance are most critical for this challenging task. Here, we examined how body size, acceleration and obstacle orientation affect the flight of bumblebees in an artificial, cluttered environment. Non-steady flight performance is often predicted to decrease with body size, as a result of a presumed reduction in acceleration capacity, but few empirical tests of this hypothesis have been performed in flying animals. We found that increased body size is associated with impaired flight performance (specifically transit time) in cluttered environments, but not with decreased peak accelerations. In addition, previous studies have shown that flying insects can produce higher accelerations along the lateral body axis, suggesting that if maneuvering is constrained by acceleration capacity, insects should perform better when maneuvering around objects laterally rather than vertically. Our data show that bumblebees do generate higher accelerations in the lateral direction, but we found no difference in their ability to pass through obstacle courses requiring lateral versus vertical maneuvering. In sum, our results suggest that acceleration capacity is not a primary determinant of flight performance in clutter, as is often assumed. Rather than being driven by the scaling of acceleration, we show that the reduced flight performance of larger bees in cluttered environments is driven by the allometry of both path sinuosity and mean flight speed. Specifically, differences in collision-avoidance behavior underlie much of the variation in flight performance across body size, with larger bees negotiating obstacles more cautiously. Thus, our results show that cluttered environments challenge the flight capacity of insects, but in surprising ways that emphasize the importance of behavioral and ecological context for understanding flight performance in complex environments.

Dispersal traits drive the phylogenetic distance decay of similarity in Neotropical stream metacommunities

AbstractAimThe drivers of phylogenetic beta diversity include both local processes (e.g. environmental filtering) and regional processes (e.g. dispersal limitation). The role of environmental filtering can be investigated more directly by analysing community–environment associations, but dispersal limitation is one of the most challenging processes to examine. We investigated the role of traits related to dispersal – flight capacity, body size and voltinism – as drivers of phylogenetic distance decay relationships in Neotropical stream insect communities.LocationHeadwater streams spread over 600 km in south‐eastern Brazil.MethodsWe compiled a data set of aquatic insect communities inhabiting streams across the State of São Paulo (Brazil). Then, we investigated environmental and spatial signals on phylobetadiversity patterns of aquatic insects using Mantel tests, multiple regressions on distance matrices and variation partitioning. We employed null models to investigate whether phylogenetic distance decay differed from pure compositional distance decay. We deconstructed the data set based on dispersal‐related traits; we then ran distance decay analyses for these subsets separately.ResultsGeographical distance, rather than environmental distance, better explained the patterns of phylobetadiversity. We found that the phylogenetic decay relationship differed from the relationship expected for the null models only for univoltine, large‐bodied genera with a high‐flight capacity.Main conclusionsDispersal limitation, rather than species sorting, was the main driver for phylogenetic beta diversity in the metacommunity that we studied. We suggest that life‐history strategies and mainly voltinism drive the distance decay of similarity in the insect communities examined. We additionally discuss the role of dispersal events over time to explain differences in distance decay patterns among tropical and other regions.

Energy allocation during the maturation of adults in a long-lived insect: implications for dispersal and reproduction.

Energy allocation strategies have been widely documented in insects and were formalized in the context of the reproduction process by the terms 'capital breeder' and 'income breeder'. We propose here the extension of this framework to dispersal ability, with the concepts of 'capital disperser' and 'income disperser', and explore the trade-off in resource allocation between dispersal and reproduction. We hypothesized that flight capacity was sex-dependent, due to a trade-off in energy allocation between dispersal and egg production in females. We used Monochamus galloprovincialis as model organism, a long-lived beetle which is the European vector of the pine wood nematode. We estimated the flight capacity with a flight mill and used the number of mature eggs as a proxy for the investment in reproduction. We used the ratio between dry weights of the thorax and the abdomen to investigate the trade-off. The probability of flying increased with the adult weight at emergence, but was not dependent on insect age or sex. Flight distance increased with age in individuals but did not differ between sexes. It was also positively associated with energy allocation to thorax reserves, which increased with age. In females, the abdomen weight and the number of eggs also increase with age with no negative effect on flight capacity, indicating a lack of trade-off. This long-lived beetle has a complex strategy of energy allocation, being a 'capital disperser' in terms of flight ability, an 'income disperser' in terms of flight performance and an 'income breeder' in terms of egg production.

Infection of an Insect Vector with a Bacterial Plant Pathogen Increases Its Propensity for Dispersal.

The spread of vector-transmitted pathogens relies on complex interactions between host, vector and pathogen. In sessile plant pathosystems, the spread of a pathogen highly depends on the movement and mobility of the vector. However, questions remain as to whether and how pathogen-induced vector manipulations may affect the spread of a plant pathogen. Here we report for the first time that infection with a bacterial plant pathogen increases the probability of vector dispersal, and that such movement of vectors is likely manipulated by a bacterial plant pathogen. We investigated how Candidatus Liberibacter asiaticus (CLas) affects dispersal behavior, flight capacity, and the sexual attraction of its vector, the Asian citrus psyllid (Diaphorina citri Kuwayama). CLas is the putative causal agent of huanglongbing (HLB), which is a disease that threatens the viability of commercial citrus production worldwide. When D. citri developed on CLas-infected plants, short distance dispersal of male D. citri was greater compared to counterparts reared on uninfected plants. Flight by CLas-infected D. citri was initiated earlier and long flight events were more common than by uninfected psyllids, as measured by a flight mill apparatus. Additionally, CLas titers were higher among psyllids that performed long flights than psyllid that performed short flights. Finally, attractiveness of female D. citri that developed on infected plants to male conspecifics increased proportionally with increasing CLas bacterial titers measured within female psyllids. Our study indicates that the phytopathogen, CLas, may manipulate movement and mate selection behavior of their vectors, which is a possible evolved mechanism to promote their own spread. These results have global implications for both current HLB models of disease spread and control strategies.

Spatial distribution, territoriality and sound production by tropical cryptic butterflies (Hamadryas, Lepidoptera: Nymphalidae): implications for the ''industrial melanism" debate

Las Hamadryas son mariposas neotropicales que emiten sonido y pasan mucho tiempo posadas en árboles, donde son crípticas. Se estudió cinco especies en Costa Rica y Panama. Cada especie tiene una altura característica para posarse. Se posaron menos del lado sur de los árboles y evitaron las partes soleadas en días calurosos. Los machos dejaron su percha para volar hacia otras Hamadryas y hacia "mariposas" de cartón. Cuando se retiró los machos de los árboles éstos fueron tomados con mucha mayor frecuencia por otros machos. La mayoría de las interacciones aéreas de H. femnia se dieron entre las 1 3 : 00 y las 1 5 :00 h y fueron más frecuentes en la estación lluviosa. De noche, los machos compartían los árboles. El sonido característico del grupo es producido por venas modificadas en las alas delanteras.

Flight behavior of foraging and overwintering brown marmorated stink bug, Halyomorpha halys (Hemiptera: Pentatomidae).

Brown marmorated stink bug, Halyomorpha halys (Stål), is a highly polyphagous invasive species attacking both cultivated and wild plants increasing its threat to ecosystems as a global pest. However, dispersal biology of this invasive species is not well understood. This study evaluated the flight capacity and behavior of H. halys under laboratory, semi-field, and field conditions. Flight mills were used to measure the baseline flight capacity of adults collected year round from the field and included both foraging and overwintering populations. The effects of abiotic conditions such as wind speed and temperatures on the free flight parameters of H. halys were evaluated under semi-field and field conditions. The mean flight distances over a 22-h period were 2442 and 2083 m for male and female, respectively. Most individuals (89%) flew <5 km, though some flew much further with a maximum flight distance observed of 117 km. Flight distances by H. halys increased after emergence from overwintering sites in spring and reached their highest point in June. The incidence of take off by H. halys was significantly affected by the wind speed; when provided with still air conditions, 83% of individuals took off, but the rates decreased to <10% when wind speed was increased to or above 0.75 m s-1. The incidence of take off by H. halys was significantly affected by ambient temperature and light intensity in the field, whereas relative humidity and insect sex did not. When the temperature was at 10-15°C, 3% of individuals took off, but the proportion of H. halys taking flight increased to 61, 84, and 87% at 15-20, 20-25, and 25-30°C, respectively. In the field, prevailing flight direction was biased toward the opposite direction of the sun's position, especially in the morning. The implications of H. halys flight biology are discussed in the context of developing monitoring and management programs for this invasive species.

Inbreeding compromises host plant defense gene expression and improves herbivore survival

Inbreeding commonly occurs in flowering plants and often results in a decline in the plant's defense response. Insects prefer to feed and oviposit on inbred plants more than outbred plants – suggesting that selecting inbred host plants offers them fitness benefits. Until recently, no studies have examined the effects of host plant inbreeding on insect fitness traits such as growth and dispersal ability. In a recent article, we documented that tobacco hornworm (Manduca sexta L.) larvae that fed on inbred horsenettle (Solanum carolinense L.) plants exhibited accelerated larval growth and increased adult flight capacity compared to larvae that fed on outbred plants. Here we report that M. sexta mortality decreased by 38.2% when larvae were reared on inbred horsenettle plants compared to larvae reared on outbreds. Additionally, inbred plants showed a notable reduction in the average relative expression levels of LIPOXYGENEASE-D (LoxD) and 12-OXOPHYTODIENOATE REDUCTASE-3 (OPR3), two genes in the jasmonic acid signaling pathway that are upregulated in response to herbivore damage. Our study presents evidence that furthers our understanding of the biochemical mechanism responsible for differences in insect performance on inbred vs. outbred host plants.

Resource Allocation to Flight in an Outbreaking Forest Defoliator Malacosoma disstria.

Allocation of larval nutrients affects adult life history traits in insects. This study assessed the effect of moth age and wing loading on flight capacity in an outbreaking forest lepidopteran, Malacosoma disstria Hübner . Insects were collected from high and low density populations after larval feeding, and flight capacity was tested directly with flight mills and indirectly through the allometric relationship between wing area and body size. Insects from these same populations collected as eggs and fed with a synthetic diet in the laboratory were tested in a separate experiment. Male moth propensity to fly increased with wing loading only when moths were collected as pupae after feeding in the field at high population densities. Moth age and wing loading did not affect the distance flown by male moths in any of the population density-nutrient regime combinations tested. Energy use increased with flight distance in both experiments. The slope of the allometric relationship between wing area and body mass did not differ from isometry when moths were collected as pupae after feeding at low and high population densities in the field. The slope of this relationship was steeper for males collected from high than low population densities. There was no allometric relationship between wing area and body mass of moths collected from these same populations as eggs and fed ad libitum in the laboratory as larvae. The results suggest that male M. disstria can allocate resources to different life history traits in response to differences in population density.

Knockdown of a putative alanine aminotransferase gene affects amino acid content and flight capacity in the Colorado potato beetle Leptinotarsa decemlineata.

Alanine aminotransferase (ALT) plays important physiological and biochemical roles in insect. In this study, a full-length Ldalt cDNA was cloned from Leptinotarsa decemlineata. It was ubiquitously expressed in the eggs, larvae, pupae and adults. In the adults, Ldalt mRNA was widely distributed in thorax muscles, fat body, midgut, foregut, hindgut, Malpighian tubules, ventral ganglion and epidermis, with the expression levels from the highest to the lowest. Two double-stranded RNAs (dsRNAs) (dsLdalt1 and dsLdalt2) targeting Ldalt were constructed and bacterially expressed. After adults fed on dsLdalt1- and dsLdalt2-immersed foliage for 3day, Ldalt mRNA abundance was significantly decreased by 79.5 and 71.1%, and ALT activities were significantly reduced by 64.5 and 67.6%, respectively. Moreover, silencing Ldalt affected free amino acid contents. Lysine was decreased by 100.0 and 100.0%, and arginine was reduced by 87.5 and 89.4%, respectively, in the hemolymph from dsLdalt1- and dsLdalt2-ingested beetles, compared with control ones. In contrast, proline was increased by 88.7 and 96.4%. Furthermore, ingestion of dsLdalt1 and dsLdalt2 significantly decreased flight speed, shortened flight duration time and flight distance. In addition, knocking down Ldalt significantly increased adult mortality. These data imply that LdALT plays important roles in amino acid metabolism and in flight in L. decemlineata.

Barb geometry of asymmetrical feathers reveals a transitional morphology in the evolution of avian flight.

The geometry of feather barbs (barb length and barb angle) determines feather vane asymmetry and vane rigidity, which are both critical to a feather's aerodynamic performance. Here, we describe the relationship between barb geometry and aerodynamic function across the evolutionary history of asymmetrical flight feathers, from Mesozoic taxa outside of modern avian diversity (Microraptor, Archaeopteryx, Sapeornis, Confuciusornis and the enantiornithine Eopengornis) to an extensive sample of modern birds. Contrary to previous assumptions, we find that barb angle is not related to vane-width asymmetry; instead barb angle varies with vane function, whereas barb length variation determines vane asymmetry. We demonstrate that barb geometry significantly differs among functionally distinct portions of flight feather vanes, and that cutting-edge leading vanes occupy a distinct region of morphospace characterized by small barb angles. This cutting-edge vane morphology is ubiquitous across a phylogenetically and functionally diverse sample of modern birds and Mesozoic stem birds, revealing a fundamental aerodynamic adaptation that has persisted from the Late Jurassic. However, in Mesozoic taxa stemward of Ornithurae and Enantiornithes, trailing vane barb geometry is distinctly different from that of modern birds. In both modern birds and enantiornithines, trailing vanes have larger barb angles than in comparatively stemward taxa like Archaeopteryx, which exhibit small trailing vane barb angles. This discovery reveals a previously unrecognized evolutionary transition in flight feather morphology, which has important implications for the flight capacity of early feathered theropods such as Archaeopteryx and Microraptor. Our findings suggest that the fully modern avian flight feather, and possibly a modern capacity for powered flight, evolved crownward of Confuciusornis, long after the origin of asymmetrical flight feathers, and much later than previously recognized.

GENETICS AND BIOLOGY OF THE MANGO BLOSSOM GALL MIDGE, PROCONTARINIA MANGIFERAE, A PEST WITH HIGHLY ADAPTABLE LIFE STRATEGIES

The development of Integrated Pest Management (IPM) on mango requires the knowledge of the biological cycle of the main pests and of their relationships with the mango tree. Among them, the mango blossom gall midge, Procontarinia mangiferae (Felt), is a monophagous invasive pest of mango, causing economic damage by attacking inflorescences. The objective of this study was to improve our knowledge on the biology of this species in the subtropical Reunion Island (i) by describing its genetic diversity and ecological abilities in order to evaluate the determinants of its genetic structure, (ii) by carrying out field and controlled experiments to understand the diapause strategies involved in maintaining populations from one flowering season to another, (iii) by modeling the female dispersion within and between orchards in relation to the mango phenological stages and their flight capacity. Our results showed that P. mangiferae was the only mango midge species feeding on both inflorescences and young leaves, present all year round at all of the sampled sites on the island, regardless of the climatic and cultural conditions. Secondly, diapause mechanisms allowed a developmental arrest at the final larval instar, lasting between six weeks to more than one year. Thirdly, female gall midges were able to colonize all trees of an orchard from external sources, but they were attracted differently by trees within the orchard in relation to the abundance and the phenology of the susceptible organs. These results illustrated the ecological plasticity of P. mangiferae. Consequences of these results to elaborate IPM strategies against the mango blossom gall midge are discussed. (Resume d'auteur)

Influence of Temperature on Flight, Walking and Oviposition Capacities of two Aphid Parasitoid Species (Hymenoptera: Aphidiinae)

The cotton aphid, Aphis gossypii Glover (Hemiptera: Aphididae) is one of the major pests of many greenhouse crops. The aphid parasitoids, Aphidius colemani Viereck and Aphidius matricariae (Haliday) (Hymenoptera: Braconidae: Aphidiinae) have been considered good agents for the biological control of A. gossypii. In Mediterranean area, these parasitoids can currently be released under elevated temperature conditions. However, few findings on their behavior changes with temperature are available. In this study, we analyze the consequence of constant temperatures ranging from 20 to 32 °C on the flight, walking and oviposition capacities of Aphidius colemani and Aphidius matricariae. Our results revealed that flight capacity is clearly influenced by temperature. The optimal temperatures for flying are 20 and 25 °C for A. colemani and A. matricariae, respectively. For both species, we observed an increase in the walking capacity but a decrease in the reproductive potential at higher temperatures. Furthermore, regardless of the tested temperature, the mummy production rate was always higher in A. colemani than in A. matricariae. These results indicate that A. colemani is more suitable than A. matricariae for the biological control of A. gossypii in Mediterranean environments. © 2015, Springer Science+Business Media New York.

Are wildlife overpasses of conservation value for birds? A study in Australian sub-tropical forest, with wider implications

A major conservation objective of wildlife overpasses is to maintain levels of dispersal between fragmented areas of habitat, thereby allowing gene-flow and sustaining population viability of target species. We documented crossing rates of a range of avian species, of four defined species guilds, over a vegetated 15m wide wildlife overpass in suburban Brisbane, south-eastern Queensland, Australia. The overpass spanned a 60m wide major arterial road, and linked two areas of isolated sub-tropical eucalyptus forest. Crossing rates of these species guilds were also determined over the major road, and two other high-traffic roads, 20 and 90m wide respectively.Species guilds differed markedly in their crossing rates of the overpass, and in their method of crossing. They also differed in their relative ability to cross high-traffic roads of different width. Our results indicate that, although honeyeater and large forest insectivore guilds made extensive use of the wildlife overpass as a foraging resource and as a conduit between forest areas, the conservation value of wildlife overpasses in relation to potential gene-flow lies mainly with the small insectivore species guild, predominantly with forest-dwelling species of lower bodyweight and with flight characteristics not well-suited to sustained direct flight. Differences between species within this guild may be linked to a range of inter-related factors, including flight capacity, habitat use, and evolutionary history.Overpasses specifically for birds have rarely, if ever, been constructed. It would, however, be relatively simple to incorporate narrow, linear strips of appropriate vegetation strata into multi-purpose overpasses to benefit these target species.

Analysis of the population genetic structure of Rhynchophorus ferrugineus in Fujian, China, revealed by microsatellite loci and mitochondrial COI sequences

AbstractThe red palm weevil (RPW), Rhynchophorus ferrugineus (Olivier) (Coleoptera: Curculionidae: Rhynchophorinae), which is one of the most serious pests of palm plants, was first found in China in the city of Wenchang (Hainan Province) in the 1990s and has now expanded to South China, including Fujian Province. In this paper, we provide a genetic characterization and determine the genetic relationships among geographic populations of RPW in Fujian using microsatellite loci and cytochrome oxidase subunit Ι (COI) sequences. The results indicate a low‐level microsatellite diversity of RPW. Four genetic clusters of RPW were found in Fujian. No correlation was detected between the genetic and geographical distances in the microsatellite data. The mitochondrial COI sequence analyses revealed a high level of diversity in the Fujian populations. Eleven haplotypes were detected, and these included eight haplotypes that were different from those found earlier in Mediterranean, Middle East, Japanese, and other populations. Significant genetic variations were observed mainly within populations, both with microsatellites and with COI sequences. Low gene flow among the populations was observed. Our results indicate that the nuclear allelic diversity was low compared with the microsatellite results from populations in Wardan and Oman, but the mitochondrial diversity was not reduced to a similar extent. The low level of the genetic structure of RPW is related to the limited flight capacity of RPW and human‐aided dispersal rather than to the geographic distance.

The influence of temperature on the flight capacity of emerald ash borer Agrilus planipennis and its parasitoid, Tetrastichus planipennisi: implications to biological control

The success of classical biological control programs often hinges on an appropriate climatic match between a novel ecosystem and an imported natural enemy. In particular, temperature is the most important factor mediating survival, developmental synchrony, and dispersal of invasive pests and their natural enemies. We used computer-monitored flight mills to investigate the roles of temperature and humidity in the flight distance, flight speed, number of flights, and post-flight mortality of emerald ash borer Agrilus planipennis Fairmaire (Coleoptera: Buprestidae) and its parasitoid Tetrastichus planipennisi Yang (Hymenoptera: Eulophidae) in laboratory settings. Flight distance had a concave, parabolic relationship with temperature for both insects. Maximum flight distances in 24 h occurred at 27.9 °C (1.13 km) for emerald ash borer and 26.5 °C (1.81 km) for T. planipennisi. Flight speed and post-flight mortality increased with temperature for both insects. Relative humidity was inversely related to flight speeds for emerald ash borer, but positively correlated with the number of flights and post-flight survival by T. planipennisi. We integrated the relationship between flight distance and temperature for both insects with landscape temperatures and flight periods for insects at ten locations across the continental USA to develop a flight index. The flight index offers a relative scale of flight capacity across locations based solely on temperature. We found that the flight index for Detroit was intermediate to low compared to other locations, with the smallest and largest flight indices projected in Minneapolis and Seattle for emerald ash borer and Seattle and Atlanta for T. planipennisi. The implications of results for host–parasitoid dispersal patterns and release protocols for distributing T. planipennisi are discussed.

Costly Nutritious Diets do not Necessarily Translate into Better Performance of Artificially Reared Fruit Flies (Diptera: Tephritidae)

Protein, lipid, carbohydrate, and energy contents of three artificial diets (Xal2, Met1, and Met2) used for laboratory-rearing and mass-rearing the Mexican fruit fly, Anastrepha ludens (Loew), for a sterile insect technique program were measured. The larval survival, pupation, pupal weight, adult emergence, sex ratio, and flight capacity of the flies reared on each of these diets were also quantified. The diet with the highest nutrient and energy content was Xal2 followed by Met2 and Met1, but larval recovery and percent pupation was significantly higher in flies reared on either the Met1 or Met2 diets. A. ludens reared on Xal2 exhibited the highest proportion of adults capable of flight. No other response variable differed significantly among the three diets tested. This suggests that a high content of nutrients and multiple sources of protein (dried yeast and wheat germ in the case of the Xal2 diet) do not necessarily improve overall performance or fly quality. We conclude that nutritious diets for A. ludens can be modified to reduce their cost without compromising the performance of artificially reared flies.

Flight Capacity ofBactrocera dorsalis(Diptera: Tephritidae) Adult Females Based on Flight Mill Studies and Flight Muscle Ultrastructure

The oriental fruit fly, Bactrocera dorsalis (Hendel) (Diptera: Tephritidae), is considered a major economic threat in many regions worldwide. To better comprehend flight capacity of B. dorsalis and its physiological basis, a computer-monitored flight mill was used to study flight capacity of B. dorsalis adult females of various ages, and the changes of its flight muscle ultrastructures were studied by transmission electron microscopy. The flight capacity (both speed and distance) changed significantly with age of B. dorsalis female adults, peaking at about 15 d; the myofibril diameter of the flight muscle of test insects at 15-d old was the longest, up to 1.56 µm, the sarcomere length at 15-d old was the shortest, averaging at 1.37 µm, volume content of mitochondria of flight muscle at 15-d old reached the peak, it was 32.64%. This study provides the important scientific data for better revealing long-distance movement mechanism of B. dorsalis.

Scientific Opinion on the pest categorisation of Circulifer haematoceps and C. tenellus

The Panel on Plant Health performed a pest categorisation of Circulifer tenellus (Ct) and C. haematoceps (Ch) (Hemiptera, Cicadellidae) for the European Union (EU) territory. They are well-defined insect species that can be identified on the basis of external morphology and male genitalia. Ch and Ct are considered to originate from the Old World; Ct is also present in North America and the Caribbean. In the EU, Ch is reported in 11 Member States, mostly in southern or central Europe, and Ct is reported in Spain, France, Italy and Greece. Neither species is harmful by itself, but they are vectors of Spiroplasma citri, the causal agent of, for example, citrus stubborn disease. The major impact of Ct in North America results from the transmission of Beet curly top virus to sugarbeet. Ct also transmits ‘Candidatus Phytoplasma trifolii’ and Ch transmits ‘Ca P. asteris’. There is no transovarial transmission of the pathogens. Ch and Ct are regulated harmful organisms in the EU and listed in Annex II, Part A, Section II, of Council Directive 2000/29/EC together with Spiroplasma citri and with respect to plants of Citrus Fortunella Poncirus and their hybrids, other than fruit and seeds, despite the fact that Ct and Ch have a larger host range. Ch and Ct are likely to be disseminated by plants for planting (the eggs are laid into the leaf veins and petioles), they have also been observed to hitch-hike on terrestrial vehicles, and Ct is known for its very high flight capacity. Both species have many hosts, in particular in the Chenopodiaceae, Brassicaceae and Asteraceae. Ecological conditions in the risk assessment area are suitable for the establishment and spread of S. citri, at least where citrus is currently grown.

Factors affecting the flight capacity of Tetrastichus planipennisi (Hymenoptera: Eulophidae), a classical biological control agent of Agrilus planipennis (Coleoptera: Buprestidae).

The dispersal characteristics of a biological control agent can have direct implications on the ability of that agent to control populations of a target host. Tetrastichus planipennisi Yang (Hymenoptera: Eulophidae) is a parasitic wasp native to eastern Asia that has been introduced into the United States as part of a classical biological control program against the emerald ash borer Agrilus planipennis Fairmaire (Coleoptera: Buprestidae). We used computer-monitored flight mills to investigate the role of age, feeding status, mating status, and size on the flight capacity of female T. planipennisi over a 24-h period. We also compared flight capacity between sexes. Flight distance of female T. planipennisi representative of populations released in the biological control program averaged 1.26 km in 24 h with a maximum flight of just over 7 km. Median flight distance, however, was 422 m. The flight capacity of females fed a honey-water solution was 41× that of females provided only water, who flew very little. Larger females were capable of flying farther distances, but age did not affect the flight capacity of females up to 70 d posteclosion. Females dispersed 6× farther than did their smaller, male counterparts. The implications of our findings to host-parasitoid interactions and release protocols for distributing T. planipennisi are discussed.