Impaired flight ability--a cost of reproduction in female blue tits

When prey are attacked by predators, escape ability has an obvious influence on the probability of survival. Laboratory studieshave suggested that flight performance of female birds mightbe affected by egg production. This is the first study of changesin take-off ability, and thus potentially in predation risk,during reproduction in wild birds. We trapped individual maleand female blue tits repeatedly during the breeding season.Females were 14% heavier and flew 20% slower (probably as aconsequence of a lower ratio of flight muscle to body mass)during the egg-laying period than after the eggs had hatched.However, flight muscle size did not change to compensate for changes in body mass over this period. In contrast, males showedno changes in either body mass, muscle size, or flight abilityover the same period. Furthermore, the impairment of flightin females increased with the proportion of the clutch thathad been laid, an effect that was independent of body mass and muscle size. This indicates that egg production causes additional physiological changes in the female body that produce impairedlocomotor performance. We suggest that courtship feeding offemale blue tits by their mates might reduce predation riskduring the period when female take-off ability is impairedby reducing the time females have to spend foraging and thusreducing the time they are exposed to increased predation.     

Take-off flight performance in the butterfly Pararge aegeria relative to sex and morphology: a quantitative genetic assessment

Adult fitness components may strongly depend on variation in locomotory performance such as flight; this variation can be sex specific. Fast take-off to intercept females and competing males is an essential behavioral component of the territorial perching behavior in male speckled wood butterflies (Pararge aegeria L.). Females on the other hand avoid frequent take-offs particularly under suboptimal temperatures, typically showing fewer but longer flights than males. We estimated the heritability of take-off acceleration performance under suboptimal body temperatures by a restricted maximum-likelihood model. We calculated genetic correlations between this performance and a selection of morphological traits: size (body mass), flight muscle investment (relative thorax mass), and wing shape (forewing aspect ratio). Our results show significant additive genetic variation for mean acceleration performance and a similar but nonsignificant trend (P= 0.08) for maximal acceleration performance during take-off in males (h(2)= 0.15). In females, heritability was not significantly different from zero for either of the acceleration performance measures. Morphological traits and take-off performance were genetically linked in a sex-specific way. In males, relative thorax mass and forewing aspect ratio were positively genetically correlated with acceleration performance. In females, there was a negative genetic correlation between acceleration performance and abdomen mass, but not with residual abdomen mass (i.e., regressed on total body mass). To fully understand the evolution of sexual differences in flight performances and morphology, several other flight performances will have to be included. This multifunctional nature of flight and its consequences for the evolutionary study of flight has not yet been fully appreciated in the literature.     

Spring behavioral patterns of the apple blossom weevil

Individual pairs of overwintered adult apple blossom weevils, Anthonomus pomorum (L.), confined with apple twigs under different ambient temperatures in the laboratory and on apple trees in the field, were observed through day and night for their spring activities. Flight behavior in relation to ambient temperature was also investigated under laboratory conditions using flight stands. Both sexes displayed predominantly nocturnal behavior patterns in both the laboratory and the field. Feeding, crawling, and mating activities increased following sunset in the field or onset of scotophase in the laboratory while resting occurred most frequently during daylight hours. Results of the laboratory experiments showed that temperature affected significantly the activity patterns. The diel pattern of activities became less distinctive at higher temperatures (above 15°C), and total activities in crawling, feeding, and mating were suppressed significantly at lower temperatures (below 5°C). Over 97% of the test weevils initiated take-off response from flight stands at 20°C within the 30 min trial period; however, flight initiation rarely occurred at temperatures 12°C or below. Overall, results of the laboratory and field experiments indicate that A. pomorum is a remarkably cold-adapted insect with ability to crawl, feed, and mate at a few degrees above freezing, a physiological attribute necessary for the exploitation of early stages of apple bud development in the cold early spring.     

Flight fuel related differences between solitary and gregarious locusts (Locusta migratoria migratorioides)

Abstract. Flight fuel relations of crowded and isolated Locusta migratoria migratorioides were investigated in younger (12–16 days after fledging) and older (27–30 or 27–32 days after fledging) adult males.No phase polymorphism dependent differences were found in resting haemolymph carbohydrate levels of the younger locusts.In the older age group, resting haemolymph carbohydrate levels were slightly though significantly higher in the isolated than in the crowded locusts.Injection of various doses of synthetic adipokinetic hormones (AKHs) did not induce marked changes in haemolymph carbohydrate levels and no differences were found between crowded and isolated locusts.A 30 min flight led to the same decrease in haemolymph carbohydrate levels of isolated and crowded locusts, 43.3% and 44.6% of the resting levels, respectively.We concluded, therefore, that the results do not seem to indicate that isolated locusts rely more heavily on carbohydrates as flight fuel than crowded locusts.Hyperlipaemic responses to flight were less intense in isolated than in crowded locusts, but phase polymorphism dependent differences in flight-induced increase of haemolymph lipid levels were not parallel in 12–16-day-old and 27–32-day-old males.In the younger age group the difference was mainly in the duration of flight needed to induce full response which appeared already after 20 min of flight in the crowded locusts, but only after 45 or 60 min of flight in the isolated ones.In contrast, the older isolated locusts showed markedly lower haemolymph lipid elevations than the crowded locusts even after 30, 45 or 60 min of flight.The hypothesis is forwarded that isolated locusts have a rather coarse adipokinetic strategy focused on a single long-distance migratory flight, whereas gregarious locusts possess a fine adipokinetic balance for reiterative migratory flights and saving fuel reserves for unpredictable long-distance migrations.     

The effect of diet on activity in male Calliphora vicina blowflies

ABSTRACT. The effect of diet on the activity of male Calliphora vicina R.D. (Diptera, Calliphoridae) was studied. Protein–fed males (PF) were significantly more active than males fed only on sugar and water (NPF); as a consequence they ingested more sugar. The phenomenon was probably due to PF insects spending more time in flight than NPF, as no significant differences were found between the wingbeat frequencies and flight speeds of tethered flies of the two treatments. Protein ingestion also had a physiological effect, as PF flies had heavier thoraces than NPF flies with increased titres of protein.     

Laboratory evaluation of flight performance of the plum curculio (Coleoptera: Curculionidae)

Flight performance of laboratory-reared adults of the plum curculio, Conotrachelus nenuphar (Herbst) (Coleoptera: Curculionidae), was investigated under controlled conditions by using a flight mill system. Across all insects tested (n=198), median values of total distance traveled, total flight time, and maximum uninterrupted flight time were 122.7 m day(-1), 23.5 min day(-1), and 2.0 min, respectively. The latter result indicates that flight occurred primarily in short bursts. Although females had a significantly higher body mass than males, there were no significant differences in flight performance between the two sexes. Flight during the first 24-h test period (especially the first 6 h) was dominated by escape behavior, i.e., elevated levels of activity presumably associated with attempts by the insects to regain freedom of movement; during the second 24 h, flight activity was very limited throughout the late morning and afternoon, increased around sunset, and remained high during the night. All flight performance variables decreased linearly and significantly with insect age over the age range tested (2-16 d after emergence). Nutritional status also had a significant effect, whereby insects that had been provided with apples as a food source for 2 d after emergence showed considerably improved flight performance compared with those that had been given no food or only water during the same period. There was no significant effect of mating status on flight performance of male or female insects.     

Day-flying butterflies remain day-flying in a Polynesian, bat-free habitat.

To test the theory that insectivorous bats have selected for diurnality in earless butterflies I compared the nocturnal flight patterns of three species of nymphalid butterflies on the bat-free Pacific island of Moorea with those of three nymphalids in the bat-inhabited habitat of Queensland, Australia. Nocturnal flight, measured as the ratio of deep night (1 h following sunset to 1 h preceding sunrise) to twilight night (1 h before sunset to 30 min after sunrise) activity did not differ significantly between the two locations, nor did the percentage of individuals active and I conclude that living in a bat-released habitat has not produced nocturnal flight in these insects. This result is surprising considering the potential advantages of escaping diurnally active predators and suggests that physiological adaptations (e.g. thermoregulation and/or vision) currently constrain these insects to diurnal flight. Since taxonomic records suggest that gene flow does not exist with bat-exposed conspecifics, I suggest that insufficient time has elapsed since these species migrated to Moorea to have resulted in major phenotypic changes such as diel flight preferences.     

Weight Loading and Reproductive Status Affect the Flight Performance of Pieris napi Butterflies

Weight-induced mobility reductions can have dramatic fitness consequences and winged animals are especially sensitive to the trade-off between mass and locomotion. Data on how natural weight fluctuations influence a flying insect’s ability to take off are scarce. We therefore quantified take-off flight ability in Pieris napi butterflies in relation to reproductive status. Take-off flight ability (velocity and take-off angle) under suboptimal temperature conditions was recorded with a 3D-tracking camera system and was predicted to decrease with relatively larger weight loads. Our results show that relatively larger weight loads generally reduce flight speed in male butterflies and lower take-off angles in females. However, despite having a lower wing loading, mated male butterflies flew slower than unmated males. Our study suggests that retention of weight loads associated with reproduction impairs insect flight performance.     

The effect of Metarhizium anisopliae var acridum on haemolymph energy reserves and flight capability in the desert locust, Schistocerca gregaria

Adult desert locusts, Schistocerca gregaria , 3 days after inoculation with the entomopathogenic fungus Metarhizium anisopliae var acridum , had significantly less carbohydrate and lipid in the haemolymph than controls. This was not due to reduced food intake as 3 days of complete starvation had no effect on haemolymph titres of energy reserves in controls. Furthermore injection of an extract of the corpora cardiaca (the source of adipokinetic hormone, AKH) caused a large significant increase in haemolymph lipid in mycosed locusts, indicating the availability of significant quantities of lipid in the fat body, the target for AKH. Haemolymph carbohydrate declined significantly during tethered flight of control locusts but not in mycosed individuals. An injected supplement of trehalose significantly boosted flight performance of mycosed insects but not controls. The results are discussed in the light of the hypothesis that the poor flight capability of mycosed locusts is due in part to a fungus-induced reduction in mobile energy reserves.     

Behavioral thermoregulation inpalmipenna aeoleoptera (neuroptera): Do the hypertrophied hindwings play a role?

The hypertrophied hindwings of Palmipenna aeoleoptera (Neuroptera) were examined for a possible thermoregulatory role. These wings arise from basal stalks which expand into large, flattened, darkly pigmented, and vascularized dilations. During the cooler times of the day the insects basked by crouching with the body and hindwings held horizontally in contact with rocks. As air temperatures increased, insects stilted with the hindwings held at 90° to the horizontal. Thoracic temperatures of these ectotherms correlated with air temperatures (T_thorax = 1.55T_air –10.99), with maximum recorded thoracic temperatures of 47°C. No differences were found between thoracic temperatures of males and those of females, although males had far larger hindwings. Live insects caught on rocks were consistently cooler than dead insects (operational temperature thermometers) on rocks. This may be attributed to convective cooling in flight just prior to capture, and stilting, behavior patterns that were frequent during the hottest times of the day. Thoracic temperatures of insects resting on rocks were frequently higher than operational temperature thermometers in air, suggesting that warming resulted from basking on rocks. The minimum body temperature for flight was 27°C. In the laboratory, hindwing ablation altered neither the rate (using time constants) of heating or cooling nor the equilibrium temperature of the body, showing that the hindwings play no direct role in heat uptake or loss.     

Feeding causes the appearance of a factor in the haemolymph that stimulates protein synthesis

Soon after a locust (Locusta migratoria) begins to feed, an increase in protein synthesis can be detected in the animal. Isolation of fat body shows that this tissue synthesizes protein at a faster rate in recently fed animals than it does in fasting insects. Fasting locusts injected with haemolymph from fed insects increased protein synthesis when compared with locusts injected with haemolymph from fasting locusts. The factor causing this increase was present in the haemolymph within 5 min of feeding. Feeding or direct contact with the food was not essential to increase protein synthesis. Exposure of fasting locusts to feeding insects was sufficient to elevate the rates of protein synthesis in the fasting animals.The increase inprotein synthesis was not a result of general excitation or an increase in the concentration of tryptophan or isoleucine in the haemolymph. Ecdysteroid titres were uniformly low during the first ten days of adult life. Gel filtration of the fed haemolymph revealed a low molecular weight fraction (about 600 daltons) which stimulated protein synthesis upon injection into fasting locusts.     

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

Emergence, 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.     

郑州地区夜鹭的求偶行为

2003年及2004年3~6月在河南郑州市区对夜鹭(Nycticorax nycticorax)的求偶行为进行了观察。结果表明,3月中旬至5月底雄性夜鹭表现出占区及固定的仪式化求偶行为,主要包括伸展炫耀、扬举炫耀、炫耀羽毛和配偶形成后的相互爱抚4个方面,其中前两种行为是夜鹭主要的求偶行为。在营巢地,求偶行为从早上日出之前夜鹭觅食归来开始,一直持续至日落前后。夜鹭的配偶选择包括雄性之间对巢区的竞争、雄鹭与雌鹭的相互选择等一系列过程。     

Allatectomy and sexual receptivity in females of Schistocerca gregaria

The removal of the corpora allata from immature females of Schistocerca gregaria causes the insects to enter a phase of permanent defence towards courting males. Operated control females copulate often, although they do not appear to show an active form of sexual display or attraction. Implanted corpora allata fail to restore sexual receptivity or normal ovarial development in the allatectomized females due to the inactivity of the denervated glands. The observations are discussed in relation to findings in other locusts, grasshoppers, and crickets.     

A stag beetle’s life: sex-related differences in daily activity and behaviour of <Emphasis Type="Italic">Lucanus cervus</Emphasis> (Coleoptera: Lucanidae)

The study of behavioural ecology of rare and elusive species can be challenging, but it is an important issue for monitoring populations in planning conservation actions. This is especially true for arboreal insects inhabiting old-growth forests, whose habits are scarcely known and rely on many anecdotal data, such as the stag beetle Lucanus cervus (Linnaeus, 1758). In order to gather information on daily activity and behaviour of this species, a radio-telemetry study was conducted in a relict broadleaf forest surrounded by intensively cultivated land in northern Italy. During 2014 and 2015, from May to July, 55 stag beetles (34 males, 21 females) were radio-tagged. Most of them were caught with the aid of an entomological hand net, but nine of them were captured by emergence traps set up on deadwood. Visual contact analysis confirmed that stag beetle males were less elusive than females. Males were more frequently radio-tracked in flight, females mostly underground and in proximity of deadwood. Males were mostly observed flying at sunset, and resting or walking on standing trees during the day. The combination of air temperature and humidity determined the optimal weather conditions for male flights (temperature range: 20.7–26 °C, humidity range: 65.5–78.3%). Flying at sunset, mostly performed by males, significantly increased the detectability of the species and supported the selection of the ‘transect walk at dusk’ as the best monitoring method for the stag beetle.     

The behavioural basis of a pheromone monitoring system for pea moth, Cydia nigricana

The flight and mating behaviour of the pea moth (Cydia nigricana) was studied at overwintering sites and in pea fields to see whether it could be exploited to provide early warning of adult immigration into pea crops. The field threshold temperature for take-off is 18 ^CC. Most flight activity-occurred in June and July between 16.00 and 18.00 B.S.T. with peak activity at 17.04 h. Moths were not caught in suction traps at heights above 0–4 m, but they can probably travel several km by fluttering above vegetation in winds of up to 10 km/h. Female moths produce a sex pheromone(s) highly attractive to males; ‘calling’ by females and mating occur during the period of maximum flight activity. Suction traps and egg counts detected the presence of moths in crops at about the same time. On average, sticky and water traps containing live virgin females as a lure caught respectively 17 and 130 times more males than suction traps and, on occasions, 25 and 300 times more; these attractive traps should detect the arrival of immigrants sooner than suction traps or egg counts. Extracts of virgin females dispensed from filter paper at doses of one and five female-equivalents (FE) attracted males rapidly but temporarily. Rubber dispensers with extracts of twenty FE remained attractive for 6 days. Several synthetic attractants were screened using doses of o-i mg on rubber dispensers in sticky traps. CYs-8-dodecenyl acetate and erans-8, frans-io-dodeca-dienol at doses of o-i mg were slightly attractive; the latter at doses of 1 -o mg was more attractive than twenty FE doses of extract and could be used for experimental monitoring of pea moth until its own synthetic sex pheromone(s) is available.     

Modulation of whitefly take-off and flight orientation by wind speed and visual cues

The effect of different wind speeds on take-off and flight orientation of the sweetpotato whitefly, Bemisia tabaci Gennadius (Homoptera: Aleyrodidae), was studied in the presence of a green visual stimulus which reflected 550 ± 10 nm light, or a white stimulus of the same intensity. When the white light was present, take-off was negatively correlated with wind speed. Analysis of the flight tracks of whiteflies in 0, 15 and 30 cm/s wind with the white light present showed that flight was not directed toward the stimulus in zero wind, and that insects were carried downwind as the wind increased. Net displacement downwind was significantly slower than the wind speed, indicating that B. tabaci can control its rate of displacement relative to its surroundings, and is not always passively transported by the wind. In the presence of the green visual stimulus, take-off and flight behaviour of B. tabaci was markedly different to that observed in the presence of the white light. Taking off was more likely and whiteflies made upwind orientated flights, landing on the illuminated section of the screen when it reflected green light. At all wind speeds tested, the mean ground speeds of B. tabaci were approximately 20 cm/s whether the insects were flying upwind or downwind. This uniformity of ground speed regardless of the changing effects of wind-induced drift in different directions strongly suggests that whiteflies actively control their ground speed using visual flow fields in a manner similar to all other flying insects examined thus far.     

Variation in energy reserves and role of body size in the mating system of Anopheles gambiae

Anopheles gambiae mates in flight. Males gather at stationary places at sunset and compete for incoming females. Factors that account for male mating success are not known but are critical for the future of any genetic control strategy. The current study explored variations in nutritional reserves (sugars, glycogen, lipids, and proteins) in wild‐caught swarming and resting males and evaluated the effect of body size and wing symmetry on male mating success. Our results showed that glycogen and sugar reserves are mobilized for flight. Males consume proportionally 5.9‐fold as much energy derived from sugars in swarming activities than when they are at rest. Mated males were on average bigger than unmated ones (P<0.0001). A strong correlation between the left and right wings in both mated and unmated males was found and additional analysis on fluctuating asymmetry did not show any indication of mated males being more symmetrical than unmated ones. The distribution of wing size of mated males was focused around a central value, suggesting that intermediate size of males is advantageous in the An. gambiae mating system. The results are discussed in the context of sexual selection.     

Sex-biased and body condition dependent dispersal capacity in the endangered saproxylic beetle <Emphasis Type="Italic">Osmoderma eremita</Emphasis> (Coleoptera: Cetoniidae)

The dispersal capacity of rare and endangered insect species has rarely been estimated even though it is essential for their management. For these species, laboratory based experiments are considered more appropriate for determining dispersal capacity as well as the factors influencing it. We aimed to characterize dispersal capacity of the endangered saproxylic beetle Osmoderma eremita (Scopoli, 1763) (Coleoptera: Cetoniidae). We studied the influence of sex and body condition on several parameters of dispersal (seven parameters of flight capacity measured in laboratory and pre-flight behaviour observed in the wild). Tethered flight experiments, conducted on 30 individuals collected in several regions of France, revealed: (1) maximal single flight distance of 1,454 m and maximal total flight distance of 2,361 m; (2) higher flight capacity in females than males; (3) flight speed and take-off completion decreasing with increasing body condition only for females. Additionally, 32 individuals displaying pre-flight behaviour in the wild showed similar interacting influences of sex and body condition: females initiating pre-flight behaviour had lower body condition than males. Thus, males and females have different dispersal strategies. We propose that body condition influences on dispersal capacity should be considered for species conservation by, for instance, managing adult food resources at the landscape scale and need to be taken into account in introduction programmes.     

Mate finding in the forest cockchafer, Melolontha hippocastani, mediated by volatiles from plants and females

The response of the forest cockchafer, Melolontha hippocastani F. (Coleoptera, Scarabaeidae), towards volatiles emitted by different host plants and conspecifics was tested in field experiments during the flight period at dusk. Funnel traps containing artificially damaged leaves from the host plants Carpinus betulus L. and Quercus rubra L., as well as from the non‐host plant Prunus serotina Ehrh. caught significantly more beetles than empty control traps. On the other hand, traps baited with undamaged leaves from Q. rubra did not catch significantly more beetles than empty controls. Leaves from C. betulus damaged by beetle feeding did not attract more beetles than artificially damaged leaves. By use of gas chromatography coupled with electroantennographic detection (GC‐EAD) electrophysiological responses of males and females were shown for 18 typical plant volatiles. A synthetic mixture of selected typical green plant volatiles was also highly attractive in the field. A total of 9982 beetles was caught during the field experiments, among them only 33 females. This suggests that attraction to damaged foliage during flight period at dusk is male‐specific. Field experiments testing the attractiveness of female M. hippocastani towards conspecific males by employing caged beetles and beetle extracts indicated that males of M. hippocastani use a female‐derived sex pheromone for mate location. On wired cages containing either unmated feeding females, or unmated females without access to foliage, or feeding males in combination with extracts from unmated females, significantly more males landed during the flight period than on comparable control cages containing feeding males or male extracts. A possible scenario of mate location in M. hippocastani involving feeding‐induced plant volatiles and a female‐derived sex pheromone is discussed.