Flight Propensity Research Articles

Can observation of climatic variables be used to predict the flight dispersal rates of Prostephanus truncatus?

Abstract 1 Attack by Prostephanus truncatus (Horn) (Coleoptera: Bostrichidae) on the maize and cassava stored by small‐holder farmers in Africa is sporadic, varying considerably within and between years. The risk that food in store will become infested is related to the number of beetles dispersing by flight. A means of predicting years with high dispersal rates is needed to warn farmers when to be vigilant.2 The relationship between climatic variables and pheromone trap catches was observed in a forest‐savannah transition zone in Ghana. These observations were used to devise a model using a mix of biological and empirical rules that operate on temperature and humidity data. The predicted and actual trap catch deviated by only +5% to −1% in years when there were high dispersal rates.3 The first part of the model estimates the numbers of beetles with potential for dispersal. The second part predicts the proportion likely to disperse. This is based on the apparent effect that those P. truncatus developing under low temperature conditions (about 24 °C) have a lowered propensity for flight, a response previously observed in a related species.4 The model was validated using climate data and trap catches from a woodland–savannah zone and a short grass steppe zone. With minor adjustment, the model worked well for these two habitats.

Ratio‐dependent parasitism with Trissolcus basalis (Wollaston) (Hymenoptera: Scelionidae) on egg rafts of Nezara viridula (Linnaeus) (Hemiptera: Pentatomidae): effect of experimental variables and compatibility of ‘ratio’ and ‘Holling’ models

Abstract Egg rafts of Nezara viridula were exposed to the parasitoid wasp Trissolcus basalis in experimental arenas to establish the relationship of the rates of attack and parasitism to various combinations of arena size, parasitoid density, host density and parasitoid‐to‐host ratio. Arena sizes were varied in the ratio 1:9:63, with the largest having a search area of 1.44 m2. Parasitoid and host densities were varied over a 27‐fold range. The parasitoid‐to‐host ratios used were 1:1, 3:1 and 6:1. Finding time was related to a constant factor (flight propensity), rather than to the difficulty of finding (density of hosts). Initial attack rates were therefore related only to parasitoid numbers (or density), even at the lower densities and ratios. Parasitism rates (a function of attack rate per host) were thus also strongly related to parasitoid to host ratio, regardless of densities used and arena sizes. Even reducing host density, while keeping time and parasitoid density constant, increased the parasitism rate. A ratio model for parasitism rate was therefore compatible with the data but the more explicit Holling ‘disc’ equation was also compatible because handling time was sufficiently large to make it sensitive to the ratio of parasitoids to hosts for the densities used. We conclude that the two models would predict different results if the density of host egg rafts was in a range below one per square metre.

Dispersal of the Filth Fly ParasitoidSpalangia cameroni(Hymenoptera: Pteromalidae) in a Swine Facility Using Fluorescent Dust Marking and Sentinel Pupal Bags

Abstract Fluorescent dust marking and sentinel pupal bags were used in 1998 and 1999 to examine dispersal, spatial distribution, and duration of activity of mass-released Spalangia cameroni Perkins in a swine facility. In 1998, four releases were conducted in the period May–November and in 1999 a final release was completed in August. Males were observed in large numbers on window sites shortly after releases, whereas females seemed to remain in the environment. However, in one trial, and probably due to high air temperatures in the facility, a similar flight propensity toward the window sites was noted for the females. The distribution of parasitoids was clearly aggregated within a perimeter of 3 m from the release point. The duration of activity of marked S. cameroni, measured as the number of attacked sentinel pupal bags and parasitism, declined to a low level within 2 wk from the time of release. The results are discussed in relation to release strategies of S. cameroni in control of nuisance flies.

Changes in amino acids in Cucumis melo in relation to life‐history traits and flight propensity of Bemisia tabaci

AbstractPhloem amino acids in Cucumis melo L. were measured to determine whether changes in nitrogen availability might affect life‐history traits and flight activity of Bemisia tabaci Gennadius (Homoptera: Aleyrodidae). During plant development, nineteen of the twenty common amino acids, plus hydroxyproline, citrulline, ornithine and γ‐aminobutyric acid (GABA) were identified. For most essential amino acids, there were two peaks observed: an initial large peak associated with young plants, and a later small peak associated with senescing plants. For histidine, ornithine and citrulline, medium to large peaks in relative abundance were observed in mature plants. Arginine peaked during the first few weeks of development and was no longer detectable after wk 7. Serine and glutamine/glutamic acid were the only amino acids that peaked during plant senescence. Factor analysis was used to create a reduced number of orthogonal factors, which corresponded well with the trends that were observed for the various groups of amino acids. No single or combination of factors explained a significant amount of the variability in oviposition. For both males and females, factor 1 (predominantly essential amino acids) was the single most important predictor of adult weight. As the relative concentrations of essential amino acids decreased, whitefly weights decreased. Factors 1 and 3 (predominantly histidine and ornithine) were the most important predictors of developmental time. As these amino acids decreased in relative concentration, developmental time increased. Percent emergence was positively associated with factor 1 and negatively associated with factor 6 (predominantly aspartic acid). The distributions of flight duration for whiteflies emerging from young, mature and senescing melon plants were compared and they were always skewed towards short flights; however, the frequency of long‐duration flights increased when melon plants began to senesce. Whiteflies from all plant‐age categories were capable of flying for more than 2 h with fully developed eggs, but the presence of more than four mature eggs was associated with flights of reduced duration.

Movement of plum curculio adults toward host trees and traps: flight versus walking

AbstractAdult plum curculios, Conotrachelus nenuphar (Herbst), were dislodged from branches of apple trees by tapping on 14 days between blossom petal fall and 3 weeks thereafter. They fell onto a small square of framed white cloth that was quickly but carefully moved to a position beneath or adjacent to the canopy of another apple tree.There, adults were observed for 50‐min periods from 0800–1950 h for propensity to fly from or walk off the cloth or move to hide beneath foliage on the cloth. At each position, the mean time from observation initiation until flight, walking off or hiding did not differ significantly among these behaviors (averaging 21–30 min), but significantly more flew (31–40%) than crawled off (16–19%) or hid (18–20%). Substantial walking off but no flights occurred at air temperatures below 20 °C, whereas at temperatures of 20 °C or greater, propensity for flight was usually significantly greater than that for walking off.Flights were predominantly toward the tree canopy or inter‐tree space, with only a small proportion (17% or less) toward the tree trunk or (in a parallel study) toward an unbaited black pyramid trap (mimicking a tree trunk). Walking was overwhelmingly toward the tree trunk or a black pyramid trap adjacent to the trunk. Our observations lead us to conclude that unbaited black pyramid traps next to trunks of host trees (the most attractive position) can be effective at air temperatures below 20 °C by attracting plum curculio adults that would have entered host trees by walking toward and up tree trunks.Such traps appear to be less effective at 20 °C or greater because under such conditions, adults tend to enter host trees by flight into the canopy.

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

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

Coevolution of traits determining migratory tendency: correlated response of a critical enzyme, juvenile hormone esterase, to selection on wing morphology

AbstractMigratory tendency in insects is a complex trait, composed of a suite of correlated behavioural, physiological, morphological and life history traits. We investigate the genetic and physiological basis of the coevolution of this suite of traits using laboratory lines of the wing dimorphic cricket, Gryllus firmus, selected for increasing and decreasing incidence of macroptery. Selection on wing morphology has produced strong direct responses in proportion macropterous as well as correlated (indirect) responses in wing muscle histolysis, flight propensity and fecundity. We investigate the hypothesis that these responses have been mediated by changes in the metabolism of juvenile hormone (JH) during the final nymphal stadium (the critical period for wing morph determination). Previous studies of Gryllus sp. have established that JH titre in this period is determined primarily by the activity of the degradative enzyme, juvenile hormone esterase (JHE). Assays of JHE activity in the final nymphal stadium of the replicated control and selected lines demonstrate highly significant differences in both mean activity and the probability of macroptery for a given level of activity (i.e., the threshold activity required to induce wing formation). These correlated responses in JH metabolism support the general hypothesis that the correlations among traits determining migratory tendency result at least in part from the common influence of JH during the final nymphal stadium. We discuss these results in the context of the quantitative genetic model for the evolution of polygenic, dichotomous traits (the threshold model), and present four general predictions concerning the coevolution of traits associated with ecological (i.e., trophic, life history, behavioural) dimorphisms.

BEHAVIOURAL EFFECTS OF IMIDACLOPRID, A NEW NICOTINYL INSECTICIDE, ON THE POTATO APHID, MACROSIPHUM EUPHORBIAE (THOMAS) (HOMOPTERA, APHIDIDAE)

AbstractAdult potato aphids, Macrosiphum euphorbiae (Thomas), caged on potato terminal leaflets treated systemically with imidacloprid solutions ranging between 5.4 × 10−4 and 5.4 × 10−8 mL per mL water showed a significant reduction in the distance they travelled, time taken to travel a given distance, and flight propensity but no significant differences in the frequency or duration of short probing behaviour. The frequency of adult apterous potato aphids colonizing untreated potato leaflets or leaflets treated with an imidacloprid solution (5.4 × 10−4 mL per mL water) was not significantly different, indicating no repellency. Potato aphids moving from systemically treated to untreated leaflets did not recover much and their reduced walking ability was maintained for days. A 3-day exposure to vapour from an imidacloprid solution (5.4 × 10−4 mL per mL water) did not produce significant mortality or changes in nymphal production. The daily cumulative mortality obtained by caging potato aphids on potato leaflets placed in an imidacloprid solution (5.4 × 10−7 mL per mL water) was similar to that obtained in the field, on 20-day-old plants treated at planting with imidacloprid applied at 0.02 g Ai/m. None of the rates of imidacloprid tested stimulated the dispersal of apterous or alate potato aphids.

Correlated Responses of Life History Traits, Wing Length, and Flight Propensity to Wing-Form Selection in the Whitebacked Planthopper, Sogatella furcifera (HORVATH) (Hemiptera: Delphacidae)

Different wing-forms (brachypters and macropters) of the whitebacked planthopper, Sogatella furcifera, were selected for 12 generations and correlated responses of several life history traits, wing length, and flight propensity to this selection were examined. A positively correlated response to wing-form selection was observed in nymphal developmental time, but no consistent response was observed in either fecundity or adult longevity. a significant reduction in forewing length was detected in response to selection for brachyptery. The flight propensity of macropters in the brachypterous line measured by the flight mill technique was significantly lower than that recorded in the control line. These results suggest that selection for brachypetery not only influences the incidence of brachypters but also acts to decrease the forewing length and flight propensity of macropterous individuals of the brachypterous line.

Flight behaviour of Bemisia tabaci in a vertical flight chamber: effect of time of day, sex, age and host quality

Abstract. The free‐flight behaviour of Bemisia tabaci (Gennadius) (Homoptera: Aleyrodidae), the sweet potato whitefly, was investigated in a vertical flight chamber. A mercury‐vapour lamp presented from above induced a phototactic flight response. Although flight propensity was comparable from 06.00 to 19.00 hours, flight duration was maximum between 06.00 and 10.00 hours. Males flew longer than females and their mean flight duration remained constant throughout the day. Females flew longer from 06.00 to 13.00 hours than from 13.00 to 19.00 hours. Both sexes were capable of sustaining flight for more than 2h, although less than 5% of those tested did so.Flight activity also was influenced by age and by host quality. The propensity to take off, proportion exhibiting phototactic orientation and flight duration varied with the age of the whitefly. Host quality influenced the timing of flight behaviour. Whiteflies reared on senescing plants exhibited greater take‐off rates and initiated longer phototactic flights up to 4 days following adult eclosion when compared to individuals reared on vegetative plants. Thereafter, individuals reared on vegetative plants exhibited greater response levels. Whiteflies reared on vegetative plants weighed more and survived longer than did individuals reared on senescing plants.Whiteflies that responded to the overhead light initially exhibited a strong photokinetic and phototactic response. Over the course of the flight, these responses declined and flight instability increased, as indicated by an overall decrease in the mean rate of climb, accompanied by an increase in the variability of this parameter and an increase in horizontal displacement. Although males and females displayed similar flight characteristics, females exhibited a greater rate of climb than did males, and for both sexes, individuals that flew longer than 25 min had a greater rate of climb than did individuals that flew for less than 25 min.

Influence of Larval Starvation and Adult Diet on Long-Duration Flight Behavior of the Migratory Moth Agrotis ipsilon (Lepidoptera: Noctuidae)

Starving fourth-instar Agrotis ipsilon (Hufnagel) for 4 d did not increase the propensity of 3-d-old moths to engage in long-duration (i.e., ≥1 h) continuous flights, or the duration of such flights, on flight mills. Adult diet (nothing, distilled water, or honey–water) did not significantly influence male flight propensity until 2 d of age or female propensity until 3 d of age. Male propensity to fly and flight profiles (flight duration, times of flight initiation and termination) seem to depend more upon the availability of liquids than carbohydrates, whereas female behavior is more dependent on a carbohydrate source. In all instances, the influence of both larval and adult diet stress on flight propensity and duration is negative. One would expect a positive effect if such stress factors act as cues that trigger a behavioral or physiological shift to a migratory phase. Instead, environmental factors that stress individuals seem only to decrease the already high propensity to make prolonged flights and decrease the duration of those flights.

Flight initiation in the egg parasitoid Trichogramma minutum: Effects of ambient temperature, mates, food, and host eggs

AbstractEmergence, preening, and flight initiation were studied in laboratory‐reared Trichogramma minutum Riley (Hymenoptera: Trichogrammatidae). Male parasitoids emerged first and flew before females. When both sexes were present in flight cylinders, female parasitoids flew before males. Flight propensity in males was negatively related to the number of emerging females, while flight propensity in females was independent of the number of males present. Ambient temperature significantly affected the propensity and timing of flight; between 70–80% of the parasitoids flew at 25 and 30 °C while less than 4%, mostly males, flew at 20 °C. No flights were observed at 15 °C. The presence of fresh host eggs caused a reduction in the proportion of female parasitoids that flew and a delay in the time to flight for the females that did fly. The presence of food increased the flight propensity of female parasitoids, but did not affect the timing of flight. The relationship between flight behaviour and the ‘efficiency’ of mass‐reared Trichogramma is discussed in terms of its importance for inundative release programmes.

Flight propensity and diapause incidence in five populations of the bark beetle Ips typographus in Scandinavia

AbstractEmergence from brood logs, take‐off activity and the duration of tethered flight was recorded in the first laboratory generation of the bark beetle Ips typographus L. (Coleoptera: Scolytidae) from five locations (ca 300 km apart) in Sweden and Denmark. Beetles of northerly origin emerged later from brood logs. This pattern was associated with an increasing proportion on non‐fliers towards the north. After overwintering, both the rate of development of flight activity and the proportion of non‐fliers were the same among populations. Flight duration of fliers was similar among populations and appeared unaffected by outbreak conditions.

Dispersive flight by Triatoma sordida

One hundred and thirty-two male and female Triatoma sordida were marked with fluorescent paint and released at an experimental site on the salt flats of central Argentina, distant from any inhabited dwellings. Flight by these bugs commenced just after sunset, and the bugs were then systematically searched for using portable ultraviolet lights. There was no apparent tendency for the bugs to fly in any particular direction, but those whose flight could be observed directly all seemed to fly in approximately straight lines at a height of 0·5–1 m. Of the 86 bugs that flew from the release point, 16 made trivial flights of less than 5 m, 4 landed at distances of 60–90 m away, while the other bugs were not recovered and appear to have flown further than 100 m. As expected from similar studies with T. infestans, the proportion of bugs initiating flight declined with increasing weight-length ratio, but T. sordida showed a much higher propensity for flight under these conditions than did T. infestans.

INFLUENCE OF TEMPERATURE AND LARVAL DENSITY ON FLIGHT PERFORMANCE OF DIABROTICA VIRGIFERA VIRGIFERA LECONTE (COLEOPTERA: CHRYSOMELIDAE)

AbstractThe influence of temperature and larval density on the flight performance of Diabrotica virgifera virgifera LeConte was quantified in the laboratory using a tethered flight system. Temperature had a significant influence on trivial flight performance in males and in both young (5 day) and older (25 day) females. The proportion of beetles undertaking trivial flight, and trivial flight duration and frequency peaked at temperatures around 20–25°C. Generally, males were more active than females at lower temperatures. Female beetles did not display sustained flight behavior at 15 or 35°C and males did not undertake sustained flight at 30 or 35°C. Sustained flight duration was unaffected by temperature. Rearing larvae at different densities influenced adult size but had only subtle effects on adult flight performance. Larval density significantly influenced trivial flight duration and frequency of older females and flight frequency of males but had no effect on young females. In general, trivial flight performance peaked when larvae were reared at moderate densities (500–750 per primary rearing container). In young females the propensity for sustained flight, but not flight duration, declined with increasing larval density.

Wing Dimorphisms and the Evolution of Migratory Polymorphisms among the Insecta

Many species of insects exhibit wing dimorphism, one morph having fully developed wings and the other morph having reduced wings and being incapable of flight. These wing dimorphisms provide visible manifestations of migratory polymorphisms. Since winged individuals do not, in principle, have to fly, the existence of forms with reduced wings suggests that there is a tradeoff between flight capability and other fitness components. Comparisons of the life histories of the fully winged and wing reduced morphs demonstrate that this tradeoff is most commonly expressed as a decrease in the age of first reproduction and increased fecundity in the morph with reduced wings. Given these tradeoffs, the evolution of wing dimorphism will depend upon its genetic basis, including correlations with other life history components. A review of the recent literature suggests that the heritability of wing morphology is high, and we suggest that this high heritability could be maintained, in part, by antagonistic pleiotropy. In dimorphic species, the winged morph is generally considered to be the migrant form. However, there are significant correlations, both within and among species, between the proportion of winged individuals, the proportion of winged individuals with functional flight muscles, and the flight propensity of those individuals. This suggests that the proportion of winged individuals and the propensity of the winged morph to migrate are intimately connected at both the physiological and population level. Therefore, the study of the evolution of wing dimorphism is important not only in its own right but also as a model of how migratory propensity evolves in monomorphically winged species.

GENETIC CORRELATIONS AMONG TRAITS DETERMINING MIGRATORY TENDENCY IN THE SAND CRICKET, GRYLLUS FIRMUS.

Migration by flight is an important component of the life cycles of most insects. The probability that a given insect will migrate by flight is influenced by many factors, most notably the presence or absence of fully-developed wings and functional flight musculature. Considerable variation has also been reported in the flight propensity of fully-winged individuals with functional flight musculature. We test the hypothesis that these components of migratory tendency are genetically correlated in a wing-dimorhic cricket, Gryllus firmus. Flight propensity and condition of the dorsal longitudinal flight muscles (DLM) are examined in fully-winged (LW) crickets from lines selected for increasing and for decreasing %LW, as well as from unselected control lines. Increased %LW is found to be associated with increased flight propensity among individuals with intact DLM, and with retention of functional DLM. The opposite is true for lines selected for decreased %LW. These results indicate both phenotypic and genetic correlations among behavioral, physiological, and morphological traits determining migratory tendency. We propose that these correlations may result from the multifunctional role of juvenile hormone, which has been reported to influence wing development, flight muscle development and degeneration, and flight propensity. Finally, we discuss the potential influence of genetic correlations for migratory traits on the evolution and maintenance of migratory polymorphisms in insects.

THE TREATMENT OF MONEY IN REGIONAL ECONOMICS

ABSTRACT. A survey of regional monetary theory suggests a regional segmentation of financial markets on the basis of differences in portfolio preference, or market imperfections. These possibilities are explored here using post‐Keynesian monetary theory. It is concluded that the availability of credit to a region depends more on the (potentially volatile) degree of confidence in the regional economy. The amount of liquidity thus generated depends on the propensity for capital flight due to liquidity preference. The resulting tendency for regions attracting low degrees of confidence to experience liquidity shortage will be greater the more integrated the national banking system.

Selection for Flight Propensity of Laboratory and Wild Strains of Anastrepha suspensa and Ceratitis capitata (Diptera: Tephritidae)1

A laboratory strain of a Caribbean fruit fly, Anastrepha suspense (Loew), and wild and laboratory strains of the Mediterranean fruit fly, Ceratitis capitata (Wiedemann), displayed improved flight propensity after selection procedures in the laboratory. The trait increased gradually after successive generations of rearing and remained high in both species after selection pressure was ceascd. The greatest magnitude of increase was 3-fold for a laboratory strain of A. suspensa, 3-fold for a laboratory strain of C. capitata, and 1.7-fold for a wild strain of C. capitata. The work provides a method to improve flight propensity among laboratory-reared insects as an alternative to the introduction of wild insects into the gene pool.

Flight Propensity of Anastrepha suspensa13

Anastrepha suspensa (Loew) flies, laboratory reared from bagasse diet and then sterilized with 10 kr of gamma radiation 2 days before eclosion, and unirradiated flies were compared to native flies from guava with a device which measured propensity for flight to an overhead light source. Native males were 27% more responsive (significantly less sedentary) than unirradiated males and 43% more responsive than irradiated males. Unirradiated males were 22% more responsive than irradiated males. Native females were 20% more responsive (significantly less sedentary) than unirradiated females and 29% more responsive than irradiated females. Unirradiated females were 11% more responsive than irradiated females. Since unirradiated laboratory reared flies had a lower flight propensity than unirradiated flies, irradiation could reduce the chances for survival of flies during stressful situations, such as in field release programs.