Continuous Flights Research Articles

Experimental and numerical study of an alternative technique for fruit processing: Rotary drum with inert bed for acerola pulp dehydration

Acerola is renowned as a potent natural source of vitamin C. However, its high perishability presents challenges for harnessing its health benefits. In this study, we explored an alternative method, the Rotary Dryer with Inert Bed (RDIB), to transform acerola pulp into a powdered form. Through both experimental and numerical investigations, we quantified how various operational variables affect RDIB's performance in acerola pulp dehydration. In numerical simulations using the Discrete Element Method (DEM), we analyzed the number and forces of particle collisions. We combined DEM results into a single response using a desirability function, pinpointing the optimal configuration: a drum with three continuous flights, each 25 mm long. Subsequently, experimental tests with this optimal setup considered temperature (T), inert fraction (FI), and maltodextrin concentration (M) effects on drying yield and bioactive compound levels. Multi-response optimization aimed to maximize both yield and bioactive compounds, yielding the optimal conditions: M = 6.25%, FI = 46.19%, and T = 77.2 °C. Thus, the results of this study show that RDIB efficiently dehydrates acerola pulp and has promising potential for industrial applications, facilitating the production of high-quality fruit powder.

Flight crew fatigue risk assessment for international flights under the COVID-19 outbreak response exemption policy

BackgroundIn response to the COVID-19 outbreak, the Civil Aviation Administration of China (CAAC) has formulated Implementation Measures for Exemption of Crew Duty Periods and Flight Time Restrictions during the COVID-19 Outbreak. This exemption policy imposes temporary deviations from the approved crew duty periods and flight time restrictions for some transport airlines and regulates the use of multiple crews for continuous round-trip flights. However, no research has been conducted on flight crew fatigue under this exemption policy. That is, the exemption policy lacks theoretical analysis and scientific validation.MethodsFirstly, flight plans for international flights under both the exemption and the CCAR-121 Policy schemes (with three flight departure scenarios: early morning, midday and evening) are designed, and flight plans are simulated based on the SAFE model. The Karolinska Sleepiness Scale (KSS) and the PVT objective test of alertness, both of which are commonly used in the aviation industry, are then selected for use in an empirical experimental study of flight crew fatigue on two flights subject to the exemption and CCAR-121 policies.ResultsThe SAFE model simulation found that the fatigue risk results based on flight crews for flights departing in the early morning (4:00), at noon (12:00) and in the evening (20:00) indicate that the fatigue risk levels of flight crews operating under the exemption policy are overwhelmingly lower than or similar to those operating under the CCAR-121 policy. However, there were a few periods when the fatigue risk of crews flying under the exemption policy was higher than that of crews flying under the CCAR-121 policy, but at these times, the crews flying under both policies were either at a lower level of fatigue risk or were in the rest phase of their shifts. In the experimental study section, 40 pilots from each of the early morning (4:00), noon (12:00) and evening (20:00) departures operating under the exemption policy were selected to collect KSS scale data and PVT test data during their duty periods, and a total of 120 other pilots operating under the CCAR-121 policy were selected for the same experiment. First, the KSS scale data results found that flight pilots, whether flying under the exemption policy or under the CCAR-121 policy, had overall similar KSS scores, maintained KSS scores below the fatigue risk threshold (i.e., KSS score < 6) during the flights and that the empirical KSS data and the model simulation results from the KSS data were overall identical at the test nodes during the flight and had nearly identical trends. Finally, the results of the PVT objective test indicators showed that the overall change in 1/RT of the crews flying under the exemption policy was less than or similar to that of the crews flying under the CCAR-121 policy, while the maximum change in 1/RT of the crews under both policies was between 1 and 1.5. This indicates that the overall level of alertness of the crew flying under the exemption policy is higher than or similar to that of the crew flying under the CCAR-121 policy, while the change in alertness level of the crew before and after the mission is relatively small when flying under either policy.ConclusionBased on the model simulation results and the results of the empirical study, it was verified that the overall fatigue risk level of flight crews operating under the exemption policy is lower than or similar to the fatigue risk level of flight crews operating under the CCAR-121 policy. Therefore, the exemption policy in response to the COVID-19 outbreak does not result in an overall increase in the level of flight crew fatigue risk compared to the original CCAR-121 policy.

Modeling melt conveying and power consumption of co‐rotating twin‐screw extruder kneading blocks: Part A. Data generation

AbstractMathematical models of polymer melt flow in co‐rotating twin‐screw extruders are crucial to screw design and predict processing characteristics, such as pressure distribution, back‐pressure lengths, degree of filling, melt‐temperature increase, and drive power. Twin‐screw modeling focuses predominantly on conveying elements, and kneading blocks are commonly represented with fictitious continuous flights, which significantly simplifies geometry and ignores considerable leakage flow. This work (Part A) presents a comprehensive analysis of the conveying characteristics and power demands of fully intermeshing co‐rotating twin‐screw extruder kneading blocks that considers the complex three‐dimensional geometry without geometrical simplifications. This analysis comprises the following steps: (1) dimensionless description of the geometry, (2) simplification of the governing equations, (3) formulation of novel dimensionless conveying and power parameters, and (4) a parametric design study with the novel approach of using the characteristic angular screw position, which avoids complex numerical algorithms and drastically reduces the computation required. Our comprehensive parametric design study included 1536 independent design points—a vast amount of data that revealed various effects that are highlighted in this work, including new findings on the interactions between geometry and conveying and power parameters. The obtained results serve, for example, as the basis for screw design, optimizations, scale‐up, and soft sensors.

Individual and sex‐related patterns of prolonged flights during both day and night by great reed warblers crossing the Mediterranean Sea and Sahara Desert

A wide variety of the barrier crossing strategies exist among migrating songbirds, ranging from strict nocturnal flights to non‐stop flights over a few days. We evaluate barrier crossing strategies in a nocturnally migrating songbird crossing the Mediterranean Sea and the Sahara Desert, the great reed warbler, exploring variation between the sexes and within individuals. We used data from 31 year‐round light‐level geolocators tracks from 26 individuals (13 males and 13 females), with four individuals tracked for 2–3.5 consecutive years. Almost all individuals (25 of 26) prolonged their flights into the day at least on one occasion. The mean duration of these prolonged flights was 19.9 h and did not differ between sexes or seasons. Fifteen birds performed non‐stop flights during more than one full day and night (≥ 24 h; mean = 31.9 h; max = 55 h) in autumn and/or spring, but these flights were generally too short to cross an entire barrier (such as the Sahara Desert) in one non‐stop flight. Patterns of prolonged flights showed considerable within‐individual variation in females between seasons (autumn versus spring) and in both males and females between years, suggesting high individual flexibility in migration strategy. Significantly more males than females performed prolonged flights during autumn migration, but not spring, possibly reflecting sex‐specific carry‐over effects. We conclude that great reed warblers have the ability to conduct prolonged continuous flights for up to several nights and days, which potentially would allow them to cross the Sahara Desert in one non‐stop flight. However, they typically use a mixed strategy of several nocturnal flights with intermittent stopovers in combination with 1–3 prolonged flights. Prolonged flights covered less than half (44%) of the total flight time across the barriers, and the diurnal parts of the flights covered only 18% of this time.

Rohingya Refugees Crisis between Bangladesh and Myanmar: Search for Permanent Solutions

Bangladesh is an occupied population of South Asia. India and Myanmar share the border with the neighboring states of Bangladesh. After independence in 1971, Muslims started experiencing continuous refugee flights of Muslim Rohingyas in Myanmar for fear of religious and ethnic violence. Bangladesh mostly welcomed them and provided protection under their free will, although refugees do not have any statutory legislation. No solution was found till 2013, and the number of refugee flights increased steadily. Rohingya refugees are destroying Bangladesh's reputation in international drafting and committing various offenses against fake Bangladeshi passports. Bangladesh is a contender on refugee issues: Firstly, the issue of human rights and secondly the national security problem. I have a positive and reactionary opinion that it is the right time to make Bangladesh a rigid domestic law for infiltrating Rohingyas from Myanmar.

Faith in Flux: Pentecostalism and Mobility in Rural Mozambique by Devaka Premawardhana

Reviewed by: Faith in Flux: Pentecostalism and Mobility in Rural Mozambique by Devaka Premawardhana Daria Trentini Devaka Premawardhana, Faith in Flux: Pentecostalism and Mobility in Rural Mozambique. Philadelphia: University of Pennsylvania Press, 2018. 232 pp. Faith in Flux provides an ethnographic analysis of religious and social change in Maúa, a rural district in the Niassa province of northern Mozambique, which is inhabited by the Makhuwa people. Anthropologist Devaka Premawardhana focuses on Pentecostalism in a region that was embroiled in Islamization and Catholic missionary evangelization, and where indigenous religions remain prominent in the lives of local residents. What Premawardhana found puzzling was the ease with which many Makhuwa not only joined but also left these churches, in some cases only to return again. In fact, the majority of those who remained in the churches were not local Makhuwa, but immigrants from other regions. Faith in Flux is therefore motivated by this central question: Why do Makhuwa in Maúa defect from Pentecostal churches? Premawardhana encountered similar trajectories in the migration stories of young Makhuwa, who left their villages for the opportunities of urban living, eventually returning again to their villages and peasant life, confronting delusions of economic and social progress. These decisions, though, were never definitive, as these young men often left their villages yet again for urban life, wafting back and forth. How to make sense of “these circular migrations,” both religious and spatial? Premawardhana’s engagement with this question generates a work that not only contributes to the literature on Pentecostalism and social change, but also offers a sophisticated exploration of the complexities of the Makhuwa people of Maúa. [End Page 1319] Migration and conversion overlap throughout the book, as conversion is locally conceptualized more as a migratory experience—othama meaning “to move”—than as an inward transformation—opittukuxa murima, “to change heart,” an expression that the Makhuwa rarely use (23–24). Faith in Flux, however, understands mobility as more than just spatial movement. Drawing on Ghassan Hage’s (2005) definition of existential mobility, Premawardhana sees mobility, above all else, as having a direction, as “not being stuck” (17). Each chapter is structured around a story of mobility—men and women who flee after an unexpected, mysterious death; fervent Christians who resort to healers and sorcerers in times of illness; young men who temporarily leave Pentecostal churches to embark on rituals of initiation; and women who move between churches, mosques, and spirit ceremonies, as they confront sicknesses and abusive husbands. There are also stories about those who remain, like Diniz, an old sugarcane harvester who decides to stay on his land despite the fact that his crops are continuously threatened by the invasions of elephants, since, as he laments, “There is no place without elephants. There is no other possibility” (68). For Premawardhana, this story of perseverance is also one of existential mobility—an example of agency in the face of the forces that impinge upon one’s life. Nonetheless, Faith in Flux does not interpret Makhuwa mobility merely as a resource to confront the hardships of life, the suffering of illness, and the unpredictability of the world. Nor does it reduce mobility solely to external and global forces, as is often the case with literature about social change in Africa and elsewhere. Rather, Premawardhana’s central point is that movement and transformation are intrinsic to Makhuwa tradition. Being Makhuwa is to be on the move, open to change, in a constantly kinetic state of being. Premawardhana’s ethnographic investigation of mobility occurs in three parts, each of which refers to a local concept that illuminates the centrality of mobility in the Makhuwa ethos: Othama (“to move”), Ohiya ni Ovolowa (“to leave and to enter”), and Okhalano (“to be with”). The first part—“To Move”—begins by exploring mobility within Makhuwa history, myth, and social and economic structures. Chapter 1, “A Fugitive People,” shows how the history of the Makhuwa is marked by continuous flights and migrations, the extent to which the Makhuwa can be defined as a seminomadic people. In this respect, [End Page 1320] mobility functioned as a strategy upon which the Makhuwa drew to avoid slave-trade raids and the civil war. Nonetheless...

Assessing vector navigation in long-distance migrating birds

Birds migrating between distant locations regularly perform long continuous flights lasting several days. What compass mechanism they use is still a mystery. Here, we use a novel approach, applying an individual-based model, taking compass mechanisms based on celestial and geomagnetic information and wind into account simultaneously, to investigate what compass mechanism likely is used during long continuous flights and how wind drift or compensation affects the resulting tracks. We found that for the 6 cases of long continuous migration flights, the magnetoclinic route could best explain the route selection in all except one case compared with the alternative compass mechanisms. A flight strategy correcting for wind drift resulted most often in routes ending up closest to the predicted destinations. In only half of the cases could a time-compensated sun compass explain the migration routes observed with sufficient precision. Migration from Europe to the Siberian tundra was especially challenging to explain by one compass mechanism alone, suggesting a more complex navigation strategy. Our results speak in favor of a magnetic compass based on the angle of inclination used by birds during continuous long-distance migration flights, but also a capacity to detect and correct for drift caused by winds along the route.

Energy Expenditure and Metabolic Changes of Free-Flying Migrating Northern Bald Ibis.

Many migrating birds undertake extraordinary long flights. How birds are able to perform such endurance flights of over 100-hour durations is still poorly understood. We examined energy expenditure and physiological changes in Northern Bald Ibis Geronticus eremite during natural flights using birds trained to follow an ultra-light aircraft. Because these birds were tame, with foster parents, we were able to bleed them immediately prior to and after each flight. Flight duration was experimentally designed ranging between one and almost four hours continuous flights. Energy expenditure during flight was estimated using doubly-labelled-water while physiological properties were assessed through blood chemistry including plasma metabolites, enzymes, electrolytes, blood gases, and reactive oxygen compounds. Instantaneous energy expenditure decreased with flight duration, and the birds appeared to balance aerobic and anaerobic metabolism, using fat, carbohydrate and protein as fuel. This made flight both economic and tolerable. The observed effects resemble classical exercise adaptations that can limit duration of exercise while reducing energetic output. There were also in-flight benefits that enable power output variation from cruising to manoeuvring. These adaptations share characteristics with physiological processes that have facilitated other athletic feats in nature and might enable the extraordinary long flights of migratory birds as well.

Relative sea-level history of Marguerite Bay, Antarctic Peninsula derived from optically stimulated luminescence-dated beach cobbles

Calmette Bay within Marguerite Bay along the western side of the Antarctic Peninsula contains one of the most continuous flights of raised beaches described to date in Antarctica. Raised beaches extend to 40.8 m above sea level (masl) and are thought to reflect glacial isostatic adjustment due to the retreat of the Antarctic Peninsula Ice Sheet. Using optically stimulated luminescence (OSL), we dated quartz extracts from cobble surfaces buried in raised beaches at Calmette Bay. The beaches are separated into upper and lower beaches based on OSL ages, geomorphology, and sedimentary fabric. The two sets of beaches are separated by a prominent scarp. One of our OSL ages from the upper beaches dates to 9.3 thousand years ago (ka; as of 1950) consistent with previous extrapolation of sea-level data and the time of ice retreat from inner Marguerite Bay. However, four of the seven ages from the upper beaches date to the timing of glaciation. We interpret these ages to represent reworking of beaches deposited prior to the Last Glacial Maximum (LGM) by advancing and retreating LGM ice. Ages from the lower beaches record relative sea-level fall due to Holocene glacial-isostatic adjustment. We suggest a Holocene marine limit of 21.7 masl with an age of 5.5–7.3 ka based on OSL ages from Calmette Bay and other sea-level constraints in the area. A marine limit at 21.7 masl implies half as much relative sea-level change in Marguerite Bay during the Holocene as suggested by previous sea-level reconstructions. No evidence for a relative sea-level signature of neoglacial events, such as a decrease followed by an increase in RSL fall due to ice advance and retreat associated with the Little Ice Age, is found within Marguerite Bay indicating either: (1) no significant neoglacial advances occurred within Marguerite Bay; (2) rheological heterogeneity allows part of the Antarctic Peninsula (i.e. the South Shetland Islands) to respond to rapid ice mass changes while other regions are incapable of responding to short-lived ice advances; or (3) the magnitude of neoglacial events within Marguerite Bay is too small to resolve through relative sea-level reconstructions. Although the application of reconstructing sea-level histories using OSL-dated raised beach deposits provides a better understanding of the timing and nature of relative sea-level change in Marguerite Bay, we highlight possible problems associated with using raised beaches as sea-level indices due to post-depositional reworking by storm waves.

Lipid economy, flight activity and reproductive behaviour in the speckled wood butterfly: on the energetic cost of territory holding

Insect flight is a highly energy demanding type of locomotion. In butterflies, males may locate females by different behavioural tactics. The tactics correspond to different flight types that, in turn, are assumed to reflect different energetic costs. Costs need to be considered to fully understand the pay‐offs of co‐existing alternative tactics relative to the environmental context and the phenotypes of the individuals. We addressed the issue in the speckled wood Pararge aegeria, in which males either adopt a territorial wait‐and‐fight tactic (i.e. territorial perching) in a sunlit patch on the forest floor, or a fly‐and‐search tactic to locate females in a wider area of the forest (i.e. patrolling). Perching corresponds to high frequency of take‐off flights and aerial combats with high levels of manoeuvrability and is assumed to be energetically more costly than longer, continuous flights at lower speed in patrollers. We tested the effect of different flight activity levels and of the behavioural tactics on lipid reserves and lipid use in males by laboratory and outdoor cage experiments. Low‐activity males that had access to honey water were capable of synthesizing lipids; their lipid reserves increased with age. The effect disappeared in males that actively flew in the outdoor cages. Lipid reserves decreased significantly faster in territorial perching males compared to non‐perching males, but resting metabolic rate did not differ between the alternative behavioural tactics. Territorial perching males had larger flight muscle ratio (i.e. thorax/body mass) than non‐perching males. We discuss the evidence of the physiological costs of perching relative to the co‐existence of perching and patrolling tactics.

Season and temperature dependent location of mating territories inSomatochlora flavomaculatain a heterogeneous environment (Odonata: Corduliidae)

Abstract In a heterogeneous environment, males of Somatochlora flavomaculata regularly occupy site-fixed locations away from water, adjacent to vertical landscape elements, and to a lesser extent, also at water, i.e. at oviposition sites. Territories both over land and over water are typically patrolled by continuous site-fixed flights. These places serve as rendezvous sites where copulation is initiated. The results of a seven-year study in a heterogeneous mire habitat of Central Europe with scattered oviposition sites demonstrated that the rendezvous sites changed over the flight season in both location and quality. At the beginning of the reproduction period territories were established almost exclusively over land. Subsequently, there was a significant shift from sites over land to sites over water, and towards the end of the flight season virtually all territories were situated over water. Areas with overgrown puddles were also attractive for establishing territories, even at the beginning of the fli...

Flight activity of the smaller tea tortrix, Adoxophyes honmai (Lepidoptera: Tortricidae).

Effects of sex, age, mating status and temperature on flight activity of the smaller tea tortrix, Adoxophyes honmai, were evaluated by a computer-aided flight mill system. Flight activity of both sexes peaked at 2 days old and they were capable of flying about 5 km a night. Between 1 and 4 days old, there was no significant difference in flight activity between the sexes, while females flew longer than males between 5 and 8 days old. Mating status, whether mated or unmated, did not affect flight activity of females. Both females and males flew most actively at 23°C, and their continuous long flights were reduced at temperatures under 18°C. Compared with flight activity of another tea tortrix, Homona magnanima, males of both species showed an identical pattern of age-specific flight, and flight activity of females of H. magnanima peaked at 5 days old, later than conspecific males. Suitable temperatures for female flight ranged from 20.5 to 28°C in A. honmai, and 15.5 to 23°C in H. magnanima.

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.

Reproductive Maturity, Mating Status, and Long-Duration Flight Behavior of Agrotis ipsilon (Lepidoptera: Noctuidae) and the Conceptual Misuse of the Oogenesis'Flight Syndrome by Entomologists

The relationship between long-duration flight and the state of oogenesis in the migratory moth Agrotis ipsilon (Hufnagel) was examined in unmated females 1,2,3,4, and 5 d old by using computer-interfaced flight mills. Evidence presented suggests that such long-duration flights (i.e., continuous flights ≥1 h) are indices of migratory flight. There were no significant correlations between the number of chorionated eggs and flight duration, times of flight initiation and termination, or flight speed within age classes 1–4. In 5-d-old moths, however, there was a positive correlation with flight duration. Mated females began their long-duration flights ≍3 h later in the night and averaged 2 h of flight less than unmated females. Their propensity and capacity to engage in such flights, however, was still considerable. The long-duration flight behavior of 3-d-old mated males was similar to that of unmated males, as was their propensity to engage in such flights. Therefore, a delay in oogenesis and suppression of reproductive behavior are not prerequisites for the initiation of long-duration flight activity in A. ipsilon , as would be predicted if the oogenesis-flight syndrome was characteristic of this species. Our data are consistent with previous findings that suggest that most females arrive in the midwestern United States in the spring already mated. We argue that the concept of an oogenesis-flight syndrome in migratory insects has no inherent explanatory power and its only valid use is as a convenient descriptive term. Its most frequent misuse as an explanatory principle is seen in the common assumption that duration of the prereproductive period determines the maximum duration of the migratory period. Empirical evidence as well as theoretical considerations indicate that it is never safe to accept this assumption without testing. To do so risks impeding progress in understanding specific systems through unwarranted extrapolation of data or through building a house of cards.

Comparison of Flight Ability between Wild and Mass-Reared Melon Fly, Dacus cucurditae COQUILLETT (Diptera : Tephritidae), Using a Flight Mill

Comparative studies of flight ability were conducted in one wild and two mass-reared strains of the melon fly, Dacus cucurbitae, using a flight mill. A wild strain collected from the field as larvae was reared for 2 generations on pumpkin fruit. Two mass-reared strains, herein called new and old strains, were reared for about 15 and 51 generations, respectively, in a mass-rearing facility. Although there was wide variety in the duration of continuous flights among individual adults, flies of the wild strain flew longer than those of the two mass-reared strains. In the latter, the average duration of continuous flights reached a peak at an earlier adult age than in the wild strain, and then decreased. In the wild strain, the peak average duration was reached later, but the high level was longer than in the mass-reared strains. The flight velocity of the mass-reared strains was higher than that of the wild strain. No difference in flight ability between the new and old mass-reared strains was observed. Artificial rearing over many generations under laboratory conditions seemed responsible for these results.

Laboratory observations on the flight activity of the plague locust, Chortoicetes terminifera (Walker) (Orthoptera: Acrididae)

AbstractFlight activity characteristics of Chortoicetes terminifera (Wlk.) were recorded in adults suspended on a simple flight balance in a wind tunnel. Ninety-one per cent, of flights by post-teneral (&gt;5-day-old) insects lasted less than 60 s, and only 11% of adults flew for a full 20-min test period at 30°C. The flight capacity ranged from a few or many short flights to continuous flights. Females flew for a greater proportion of the time than males. Flight activity increased with food-deprivation, and only fully hardened (&gt;9-day-old) insects flew continuously throughout a 45-min test period at 26–41°C. Gravid females also made long flights. The frequencies of flight durations by laboratory-reared insects were strikingly similar to the day flight of milling field populations in eastern Australia. Flight performance observations indicated that lift declines with time in flight, wing-beat frequency initially being 33·2 Hz in males and 30·0 Hz in females. The results are discussed in relation to field studies.

THE UTILIZATION OF GLYCOGEN BY FLIES DURING FLIGHT AND SOME ASPECTS OF THE PHYSIOLOGICAL AGEING OF DROSOPHILA

The role of glycogen in the flight physiology was studied for two species of flies, Drosophila funebris and Lucilia sericata. Glycogen was determined by microchemical methods. The flight ability was measured stroboscopically in terms of the total number of wing-beats, under standardized conditions, in continuous flights to exhaustion.Glycogen was found to be of primary importance in the physiology of flight. During continuous flight the concentration of this substance gradually decreases in both the entire animal and the thorax.The decrease in glycogen during the first stages of such flights has no marked effects on the intensity of flight, in terms of the frequency of wing-beat.Near the end of continuous flight the concentration of glycogen becomes limiting and wing-beat frequency rapidly decreases until flight ceases before the frequency becomes as low as 100 double-beats per second.Both the flight ability of Drosophila and the concentration of glycogen vary as functions of age. During the first week of adult life the average length of flight increases from 26 minutes on the first day to 110 on the seventh and the total number of wing-beats from 225,000 to more than a million. Simultaneously the glycogen concentration rises from about 2.5 to 6 per cent of the live weight. In animals older than two weeks the flight ability and glycogen concentration decrease rapidly and then more slowly until, by the thirty-third day, the average length of flight is reduced to 19 minutes (170,000 double wing-beats) and the glycogen concentration to about 3.5 per cent of the live weight. This correlation, although not exact, suggests that the physiological ageing of the flight ability results to a large degree from the simultaneous changes in the concentration of glycogen.

Migration of Birds

YESTERDAY and to-day (17th and 18th inst) continuous flights of migrant birds, chiefly fieldfares and redwings, have passed over this place in one uniform direction, from east to west, turning inland to the north-west, as though unwilling to cross Poole Harbour. The procession, so far as it attracted my own notice, began with daybreak of the 17th, and was so rapid and continuous all that day that enormous numbers altogether must have passed over us. Close flocks would come, and then a continuous flight of stragglers, but all in one and the same direction, and with little deviation from a well-defined aërial pathway, as though keeping some visible high-road, Yesterday the flight was down the wind; this morning against it; and although the flight was low and the birds seemed tired, none alighted in this neighbourhood. Whence did they come, and whither are they bound—east or west of this place? Can any of your readers say?