Role of developmental plasticity in tethered flight performance of the oriental fruit fly, <i>Bactrocera dorsalis</i> (Hendel) (Diptera: Tephritidae)

The housefly (Musca domestica L.) is well known a global pest of animals and humans. The houseflies contain high purity chitin and protein which are widely used in industry, and medicine. Their larvae can produce animal protein in the biodegradation of organic waste . House flies provide an alternative for recycling nutrients while also generating multiple income streams, so their large-scale production is important. In this study, the effects of different doses of propolis applied to a wheat bran diet on the developmental stages (larval and pupal development time, larval, pupal, and adult weight, and larval, pupal, and adult survival) and the protein, carbohydrate, and lipid content in Musca domestica larvae were examined under laboratory conditions (62±0.2% humidity and 25.06 ± 0.8°C temperature). Thirty Musca domestica larvae were reared on substrates exposed to four different propolis concentrations. One-way ANOVA was used to compare life history and biochemical parameters. The results showed that increasing concentrations of propolis reduced larval length and weight. While a decrease in the number of pupae and adults was observed, a significant increase in pupal weight was noted. Larval development time was not affected by propolis diets compared to the control, but pupal development time was shortened. In biochemical composition, no significant difference in protein content in Musca domestica larvae was observed with increasing propolis concentrations. However, compared to the control, increasing propolis concentrations increased carbohydrate content and decreased lipid content in Musca domestica larvae.

Numerous studies have examined predation risk resulting from the costs of impaired flight performance associated with many key life-history stages such as reproduction and migration. Interestingly, although avian nestlings experience multiple resourcebased physiological trade-offs and undergo considerable morphological and physiological changes during postnatal development, there is no data available on how nestlings manage the competing demands of growth and the development of flight ability at this critical life-history stage. We examined numerous morphological traits to determine which are responsible for variation in flight performance in juvenile European starlings (Sturnus vulgaris), a sexually size-dimorphic passerine. We then manipulated maternal quality during chick rearing (via feather clipping) to examine sex-specific sensitivity of fledgling flight performance to the quality of the rearing environment. Results suggest that the mechanics underlying variation in juvenile flight performance are relatively simple, being principally determined by the ratio of pectoral muscle mass to body mass (BM) and the surface area of the wings. Interestingly, although the maternal quality manipulation decreased BM and structural size in daughters, only the flight performance of sons was negatively affected. Our results suggest that a survival-related trait can be significantly affected in the larger sex when raised under stressful conditions. Furthermore, measuring only BM and structural size may not be sufficient in understanding how the sexes are affected by stressful rearing conditions in sexually size-dimorphic species. Key words: development, escape performance, european starling, flight ability, predation risk, sexual size dimorphism. [Behav Ecol]

Oogenesis-flight syndrome in crickets: Age-dependent egg production, flight performance, and biochemical composition of the flight muscles in adult female Gryllus bimaculatus

In this paper we report observations on variation in flight performance and body size among tropical, temperate, and island milkweed bugs (Oncopeltus: Hemiptera: Lygaeidae). This is one of a series of papers on life history variation in Oncopeltus; photoperiodism is discussed in Dingle et al. (1980) and size dependent timing of metamorphosis in Blakley and Goodner (1978). Other papers are in preparation. The distribution of these bugs throughout much of the Western Hemisphere (Slater, 1964) allows comparison, both within and among species, of the selective forces acting on life histories. Various species occur in tropical and temperate regions and on islands throughout the Caribbean on milkweeds (Asclepiadaceae) and occasionally on plants of related families. One species, Oncopeltus fasciatus, is a long distance migrant to temperate North America (Dingle, 1968a et seq.), while the remainder are confined to the tropics and subtropics. General discussions of the ecology of these insects may be found in Blakley (1977), Dingle (1968a et seq.), Evans (1979), Ralph (1976, 1977), Root and Chaplin (1976), and Sauer and Feir (1973); a summary is included in Dingle et al. (1980) which also gives collecting sites for the populations discussed here. Migratory physiology is reviewed by Rankin (1978). All species discussed in this paper belong to the subgenus Erythrischius (Slater, 1964). We found that flight performance differed considerably among species and populations of Oncopeltus. Dispersal abilities of insects vary with habitat (Southwood, 1962; Dingle, 1972), and many species occurring in isolated habitats, including islands, are apterous or brachypterous (Carlquist, 1974; Vepsaldinen, 1978). There are, however, only a few studies (e.g., Rose, 1972) which demonstrate that relatively shorter (as opposed to functionless) wings actually lead to reduced flight and none, so far as we know, demonstrating reduced flight in cases where it would be expected, for example, on islands, but where there is no obvious alteration in wing structure. In this report we demonstrate that reduced flight can occur with no apparent changes in wing morphology. Body size has attracted considerable attention from evolutionary biologists. It is easy to measure, and it is associated with a number of other characteristics from life history statistics (Pianka, 1970; Stearns, 1976; Blueweiss et al., 1978) to an array of morphological and physiological traits (summarized by Pyke, 1978). Despite much effort by ecologists and others, however, the adaptive significance of body size is not well understood, and indeed there seems to be no general agreement on the most important selective factors (Pyke, 1978). Body size is also frequently influenced by proximate environmental conditions such as food availability, so that analysis is complex. Regardless of such phenotypic variability, the heritability of body size differences is more often assumed than demonstrated so that their adaptive nature falls short of proof. In this study we demonstrate heritable differences in body size between bugs of island 1 Present address: Institute for Behavioral Genetics, University of Colorado, Boulder, Colorado 80309.

In the territorial damselfly Calopteryx atrata Selys, length of the hindwing, the wing areas and the aspect ratio did not differ significantly among age classes during the pre-reproductive period, while the body mass of males increased about 2.5 times. This is due primarily to increase in mass of thorax and abdomen. The flight muscle mass accounted for the great part of the thorax mass, and began to increase from early in the pre-reproductive period and continued increasing until sexual maturation. The average flight muscle mass of sexually matured males was about 2.4 times of that of the youngest immature ones. On the other hand, the abdomen mass and total lipids increased remarkably in the latter half of the pre-reproductive period. The average total lipid content of mature males was about tenfold of that of the youngest immature ones. The maximum lift production per flesh body mass was positively correlated with the flight muscle mass and total lipid content. Such an increase in flight muscle mass and lipid reserves resulted in the increase of maximum lift force, and probably enhanced flight performance.

Simple SummaryThe Asian corn borer, Ostrinia furnacalis (Guenée), is geographically widespread and enters a photoperiod-induced larval diapause with the gradually shortening daylengths of autumn. Here, life-history traits between non-diapausing and diapausing individuals were tested along a latitudinal gradient by rearing the larvae from six different geographical populations under their own critical daylengths to produce non-diapausing and diapausing individuals. In the non-diapausing pathway, the high-latitudinal populations had a significantly shorter larval developmental time and greater body weight than the low-latitudinal populations, whereas in the diapausing pathway, the high-latitudinal populations had longer larval developmental times and relatively smaller body weights than the low-latitudinal populations. This is the first report showing that life-history patterns of the two alternative developmental pathways were significantly different between the lower and higher latitudes.Individual insects often exhibit two alternative pathways of non-diapausing and diapausing developments. Yet, most studies have focused on the latitudinal variation in life-history traits for non-diapausing individuals. No study has examined the differences in life history traits between non-diapausing and diapausing individuals along a latitudinal gradient. We used six different geographical populations of Ostrinia furnacalis to examine the latitudinal variation in life-history traits between non-diapausing and diapausing individuals in terms of their sex ratio, larval and pupal developmental times, pupal weight, growth rate, adult weight and weight loss, and sexual size dimorphism. The results showed that latitudinal variation in life-history traits for both non-diapausing and diapausing individuals exhibited a sawtooth pattern, but the life-history pattern of the two alternative developmental pathways was significantly different between the high and low latitudes. For the non-diapausing pathway, the high-latitudinal populations showed a significantly shorter larval developmental time, higher growth rate and greater body weight than the low-latitudinal populations, suggesting countergradient variation. Conversely, in the diapausing pathway, the high-latitudinal populations had longer larval developmental times, lower growth rates and relatively smaller body weights than the low-latitudinal populations, suggesting cogradient variation. We also found that in the high-latitudinal populations, larvae in the non-diapausing pathway had shorter developmental time and higher body weight, whereas larval developmental time of the low-latitudinal populations was longer and the body weight was smaller. The relationship between larval developmental time and pupal weight was also different between the two developmental pathways. These results provide new insights into the evolution of life-history traits in this moth.

Bats have a great variety of wing morphologies that determines the bat’s flight performance, and this in turn conditions the forage aerosphere and the food it can obtain. Several studies have shown differences in wing morphology, flight performance, and forage aerospheres among species from different trophic guilds. However, for species that share a guild this is not entirely clear. It is possible that these species have differences in their diet and show changes in wing morphology that modify their flight performance and forage areas. Determining this will allow a better understanding of spatial segregation among species that share a trophic guild. These studies allow the identification of species assemblages based on wing morphological differences and flight performance that would not be distinguished only by guild membership. Our goal was to define the species assemblages that make up a community of Neotropical cave dwelling bats based on their trophic guild, flight performance, and forage zone. A community of Neotropical cave dwelling bats from a cave in Veracruz, Mexico was analyzed. The diet of each species was determined by means of their stomach contents and bibliographic review. In addition, aspect ratio, wing loading and tip index were calculated. Based on the wing characteristics and diet, multivariate groupings and orders were performed, as well as to define the assemblages present. According to the wing characteristics and the dietary composition, four groups of species were found that represent four different flight characteristics in terms of agility and maneuverability. There was agreement between diet and wing characteristics, and the four trophic groups were identified through canonical correspondence analysis. Correlating wing morphology, diet and forage area allows us to adequately define the assemblages of a community of bats. Regarding the hypothesis, it was found that species that share a food guild show differences in the composition of their food and wing morphology, which generate differences in flight performance and forage areas. Four assemblages differing in forage aerospheres among three trophic guilds are described: understory and facultative artrhopodivorous, semi-clearing hematophages, and facultative nectarivores. Finally, spatial segregation between the species of the families Mormoopidae and Natalidae was recognized.

Comparative Ecology of Bactrocera Cucumis (French) and Bactrocera Tryoni (Froggatt) (Diptera: Tephritidae) - Understanding the Life History Consequences of Host Selection and Oviposition Behaviour

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.

Chapter 1. Monarch butterflies are undergoing a long-term population decline, which has led to a search for potential causes underlying this pattern. One poorly studied factor is exposure to non-target pesticides on their primary host-plant, the common milkweed Asclepias syriaca, during larval development. This species frequently grows near agricultural fields in the Midwestern U.S., but the spectrum of pesticides encountered by monarch caterpillars on milkweed leaves is unknown. Further, it is unclear whether pesticide exposure can be avoided by isolating restored milkweed patches at sites far from cropland. Over 2 years, we analyzed 1,543 milkweed leaves across seven sites in northwestern Indiana for the presence and concentration of a range of commonly used agricultural insecticides, fungicides, and herbicides. Additionally, we tested the ability of local (i.e., nearest linear distance to crop field) and landscape-level (i.e., % of corn/soybean in 1km radius) variables to predict the presence of pesticides on focal milkweeds. Overall, we detected 14 pesticides−4 insecticides, 4 herbicides, 6 fungicides—on milkweeds that varied widely in their prevalence and concentration. The neonicotinoid clothianidin, the only pesticide for which toxicity data are available in monarchs, was detected in 15–25% of plants in June with nearly 60% of milkweeds at some sites testing positive (mean conc. = 0.71 and 0.48 ng/g in 2015 and 2016, respectively); however, no samples from July or August contained clothianidin. The related neonicotinoid thiamethoxam and the pyrethroid deltamethrin were detected in most (>75%) samples throughout the season, but only in the second year of the study. For thiamethoxam, isolating milkweeds 50–100m from the nearest corn or soybean field tended to decrease the concentration and likelihood of detecting residues, whereas landscape composition surrounding milkweed sites had comparatively weak predictive power. These data suggest that monarch caterpillars frequently consume a diversity of pesticides in their diet; the lethal or sublethal impacts of this exposure remain to be tested. Chapter 2. Hundreds of recent studies have voiced concern over the negative impacts of non-target pesticides on pollinator health. However, pesticide loads are highly variable across agricultural landscapes and it is unclear whether pollinators exhibit behavioral responses (e.g., aversion) that mediate their exposure risk under realistic foraging environments. We tested whether monarch butterfly (Danaus plexippus) adults and larvae base their oviposition and foraging decisions, respectively, on the presence and concentration of pesticide residues on their milkweed host-plant, Asclepias syriaca. Using a two-year dataset that quantified pesticides on milkweeds bordering corn or soybean fields, we simulated field-realistic levels for six of the most commonly detected pesticides—one insecticide, two herbicides, and three fungicides—either alone or in combination. These laboratory and greenhouse manipulations experimentally paired an untreated control with the pesticides at their mean or maximum concentrations. Butterflies placed fewer eggs on milkweeds treated with a cocktail containing all six pesticides, but only when applied at their maximum-detected concentration, resulting in ca. 30% less oviposition compared to the untreated control. Neonate (1stinstar) larvae also showed a preference for pesticide-free leaves in paired disc assays for most compounds tested, with feeding aversion observed at both mean and maximum concentrations. Later instars did not show a comparable behavior reaction to pesticide presence or concentration, but this could be partially due to the feeding-deterrent properties of the acetone solvent used. Our data provide evidence that monarchs are capable of adaptively adjusting their oviposition and foraging behaviors based on which pesticides are present on their host-plants. Yet, for gravid females, this impact was only observed at higher than average concentrations, meaning that in the field eggs are likely placed on milkweeds regardless of pesticide presence in most cases. Thus, it is unlikely that monarchs behaviorally regulate pesticide exposure risk by avoiding contaminated plants.Finally, in Chapter 3 we used a no-choice experiment to evaluate the effects of continuous exposure to field-realistic pesticide concentrations on monarch butterfly larval and pupal development time, pupal weight, adult longevity and survival. Most monarch life stages were relatively unaffected by continuous exposure to the six pesticides tested. A negative effect in wing development and length was observed when larvae were exposed to the fungicides pyraclostrobin and trifloxystrobin and the mix of all six pesticides tested. Larval stage had higher mortality than the pupal stage and instars 2 and 5 were relatively more vulnerable. The negative effect on wing span and wing development could negatively impact migration, reproduction in the short-term and population at long-term. Strategies to reduce contamination by pesticides of non-target plants and insects should be considered to protect diversity and maintain ecosystem integrity in the landscape.

1. The movement of organisms can be driven by multiple factors and has implications for fitness and the spatial distribution of populations. Insects spend a large proportion of their adult lives foraging by flying for resources; however, their capability and motivation to move can vary across individuals.2. The aims of this study were to examine interindividual and sex differences in flight performance and flight characteristics, using a flight mill bioassay, in Megarhyssa nortoni (Hymenoptera; Ichneumonidae), a parasitoid of the invasive woodwasp Sirex noctilio (Hymenoptera: Siricidae), one of the most important pests of pine afforestation worldwide. We also assessed the influence of morphological traits in combination with sex on flight and explored the cost of flight on longevity and mass loss.3. The results show a difference between sexes in flight characteristics and performance. Females show greater total distance flown than males, and have a better capacity to undergo sustained flight. Sexual size dimorphism was also found and it was noted that size positively affects distances travelled. Females have a longer life span than males, yet no differences were noted in longevity within sex between individuals that did not fly and those that flew. Age did not influence flight performance of females or impacted on post‐flight longevity. Females lost less body mass than males even after flying longer distances.4. These results suggest that sex‐specific behaviours probably govern flight abilities together with (and not only because of) morphological traits. The paper discusses sex‐specific life‐history strategies in parasitoids and their implications for biocontrol programmes.

Effect of parasitism on flight behavior of the soybean aphid, Aphis glycines

Effect of Binodoxys communis parasitism on flight behavior of the soybean aphid, Aphis glycines

Several species of stalk-eyed flies exhibit exaggerated sexual dimorphism where females favor males with longer eyespans. Longer eyespan increases a fly’s moment of inertia, and may, therefore, impact flight behavior and fitness, specifically maneuverability and predator evasion. However, these putative costs may be ameliorated by co-selection for compensatory traits, as flies with longer eyespans tend to have larger thoraces and wings, which allows them to perform turns similar to flies with shorter eyespans. Furthermore, the capacity to compensate for a potentially costly ornament may not be fixed across the life-history of the adult stage, as stalk-eyed flies achieve sexual maturity at 3-4 weeks of age, accompanied by significant growth of reproductive tissues and organs. Thus, growth of the abdomen and body mass over time may impose constraints on flight performance that may affect whether an adult reaches the age of reproductive viability. The purpose of this study was to investigate the flight performance of stalk-eyed flies and its relationship to body morphology and development. The flight performance of 1-to-30 day oldTeleopsis dalmanni(n=124) andDiasemopsis meigenii(n=83) were assessed by presenting normoxic, variable-density mixtures of heliox (O2, N2and He) in 10% increments ranging from air to pure heliox; the least-dense gas allowing flight represented maximal performance. Flight kinematics were analyzed using high-speed (5930fps) videography. Immediately following flight assessment, flies were euthanized, photographed, dissected and weighed. In both species, total body mass, thorax and abdominal mass increased across age. Wing kinematics and maximal flight capacity were associated with thorax mass, and increased with age as flies became heavier. Although flies with longer eyespans were indeed heavier, they had larger wings and thoraces; however, maximal flight capacity and kinematics were generally independent of eyespan. Thus, bearing long eye-stalks did not impair flight performance, nor did the increase in mass attributable to reproductive maturation. Instead, variation in flight performance appears associated with the development of the flight motor, and improved ratio of thorax-to-total mass, across age.

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.