凹唇壁蜂成蜂体重与取食对其飞行能力的影响

凹唇壁蜂Osmia excavata Alfken被广泛应用于我国北方果树的传粉, 而其飞行能力是影响其传粉效率的重要因素。本研究通过飞行磨吊飞试验, 评估了凹唇壁蜂雌蜂和雄蜂飞行能力的差异以及取食对其飞行能力的影响。结果表明, 凹唇壁蜂雌蜂体重（116.30 mg）显著大于雄蜂（59.80 mg） (P<0.001), 雌蜂的最大飞行速度（3.44 km/h）显著大于雄蜂（2.36 km/h）, 雄蜂的飞行距离和最大飞行速度与其飞行前体重成显著的正相关性, 雌蜂的飞行时间与其飞行前体重成显著正相关性, 而雌蜂的平均飞行速度与其体重成显著负相关性; 雌蜂的日平均飞行距离为0.23 km, 根据雌蜂以巢为中心, 采集花粉繁殖后代的生物学习性, 蜂巢之间的放置距离应少于100 m。取食蜂蜜后, 雌雄壁蜂的飞行距离、 飞行时间、 最大飞行速度均有提高的趋势, 建议在田间应用时, 可在蜂巢附近放置蜂蜜或种植其他蜜源植物给初羽化的凹唇壁蜂提供食物补充能量。本研究明确了雌、 雄壁蜂的飞行能力和出茧后补充食物对于壁蜂飞行的促进作用, 为有效地利用凹唇壁蜂进行传粉提供了理论依据。     

二点委夜蛾飞行行为特征

【目的】本研究旨在阐明二点委夜蛾的飞行行为特征,丰富二点委夜蛾飞行生物学理论,提高其预测预报水平。【方法】利用昆虫飞行磨被动吊飞系统和主动飞行监测系统,系统研究了二点委夜蛾Athdtis lepigone(M(o|¨)schler)被动飞行能力和主动飞行意愿。【结果】成虫具有较强的被动飞行潜力。室内连续吊飞80 h,雌雄蛾最远飞行距离分别达106.71 km和148.32 km,最长飞行时间分别达43.05 h和40.01h,最快飞行速度分别达7.60 km/h和8.14 km/h。雄蛾飞行潜力显著强于雌蛾,体现在飞行距离和飞行时间显著高于雌蛾,但飞行速度差异不显著。成虫蛾龄显著影响成虫飞行能力。对不同蛾龄成虫吊飞12 h的结果表明,1日龄即具备一定的飞行能力,之后逐渐增强,3日龄时飞行能力最强,雌雄蛾平均飞行距离分别为29.61 km和27.55 km,飞行时间分别为10.04 h和9.46 h,平均飞行速度分别达2.76 kn/h和2.46km/h,4日龄成虫飞行能力开始下降,但不同性别间成虫飞行能力差异不显著。蛾龄间飞行能力差异主要是由于不同蛾龄成虫的强、弱飞行个体比例不同。二点委夜蛾主动飞行呈现明显的节律行为,飞行活动主要集中在暗期(19:00—次日5:00),在光期(5:00—19:00)基本不飞行。成虫初羽化(1日龄)主动飞行意愿增强,之后飞行活动减少,但产卵开始时主动飞行活动又开始增强,到7日龄达到峰值。【结论】二点委夜蛾成虫具有较强的飞行能力,其飞行能力受蛾龄,雌雄等因素影响;飞行具有明显的节律性。     

大头金蝇的飞行能力

通过飞行磨测定和扩散观察,研究大头金蝇Chrysomya megacephala(Fabricius)的飞行能力。结果表明:雌、雄虫的平均飞行距离、平均最大飞行速度、平均飞行时间间没有显著的差异。大头金蝇的平均飞行距离25℃时达最高,为4·4783km,之后随着温度的进一步增高而逐渐下降;平均飞行时间20℃时最大,为1·2262h;最大飞行速度25℃最大,为1·2210m/s。50%,60%,70%和80%相对湿度的平均飞行距离有显著差异,分别为5·7475,0·7913,0·3850和0·7575km;50%RH的平均飞行时间最长为2·7868h,平均最大飞行速度中80%RH最高,为2·0792m/s。在塑料大棚(长30m)释放大头金蝇呈扇形扩散,最快速度0·3m/s,从一端扩散到塑料大棚的另一端所需时间平均为(2·52±0·63)min,最长需要3·08min,表现出大头金蝇有较强的飞行能力。     

营养和幼期密度对棉铃虫飞翔能力的影响

采自棉花、玉米、花生、绿豆和芝麻5种作物上的棉铃虫Helicoverpa armigera(Hubner),其飞翔能力依次为：棉花和玉米>花生>绿豆和芝麻。对室内利用人工饲料、棉铃、棉蕾和棉叶饲养的棉铃虫吊飞表明,取食人工饲料和棉铃的个体的飞翔能力数倍于取食棉叶者。成虫体重越大,飞翔能力越强。获得补充营养个体的飞翔距离是无补充营养者的2倍左右。本试验还研究了食物质量对棉铃虫卵巢发育的影响,结果显示成虫期的补充营养明显影响幼期营养较差个体的卵巢发育进程。对不同幼虫密度下发育个体的吊飞则表明成虫的飞翔能力和幼期密度关系不大。鉴于较差的营养条件和较高的幼期密度并不导致成虫飞翔能力的增加,本文认为,棉铃虫的远距离运动是成虫对羽化阶段不良环境的行为反应。     

Genetic effects on flight capacity in the beet armyworm,Spodoptera exigua (Lep., Noctuidae)

The beet armyworm, Spodoptera exigua, is an important migratory insect pest in tropical and subtropical regions worldwide. The current study investigated genetic variation in the flight capacity of both female and male moths, using a quantitative genetics approach. The offspring–parent regression showed that parents had a significant influence on the flight duration of offspring, and the heritability estimated as 0.302. The upward selection increased mean flight duration from 123.7 to 284.6 min in females and from 113.9 to 254.0 min in males during 8 h of flight test; by contrast, downward selection decreased it from 123.7 to 65.6 min in females and from 113.9 to 29.8 min in males, while it did not change significantly in either females or males of the control line over eight generations. The mean realized heritability was estimated as 0.432 based on upward selection but 0.130 on downward selection, suggesting the asymmetry of response to selection on flight capacity. Reciprocal crosses between the two selected lines confirmed the dominance of ‘long‐flying genes’ in the inheritance of flight capacity. A positive genetic correlation was found between increased flight duration and pupal weight. The presence of such additive genetic variance and covariance for flight capacity and the fitness trait, pupal weight, in the population of S. exigua may have underpinned the evolution of its migratory behaviour.     

黄地老虎飞行能力研究

黄地老虎Agrotis segetum是一种重要的农业迁飞性害虫,研究飞行生物学对明确其迁飞机理有重要意义。本项研究利用昆虫飞行磨系统对黄地老虎的飞行能力进行了测定。对实验室种群飞行能力的测定结果表明:1日龄成虫的飞行能力最弱;3日龄飞行能力最强,其24 h平均飞行时间、平均飞行距离和平均飞行速率分别达到12.16±0.74 h、48.94±3.40 km和3.76±0.12 km/h。雌蛾与雄蛾间的各项飞行参数均无显著差异,但处女成虫平均飞行距离和平均飞行速率均显著高于已交配个体。对渤海湾野外迁飞种群飞行能力的测定显示,早季节北迁个体和晚季节回迁个体的平均飞行时间和平均飞行距离无显著差异,但皆显著低于实验室种群。黄地老虎具有较强的飞行能力,日龄和交配是影响其飞行能力的关键因素。     

Heritability of flight distance for Cydia pomonella

Cydia pomonella L. (Lepidoptera: Tortricidae) is considered to be rather sedentary, but some individuals undertake flights of several kilometres in the field. This paper investigates the genetic influence on this variability. The flight capacity was measured in the laboratory by a flight mill and its heritability was estimated for two different strains. The laboratory strain was kept for more than 45 generations and the field strain from Embrach (northern Switzerland) was recently collected in the field.The multiple-trait-restricted-maximum-likelihood method was used for the estimation of genetic variances and covariances. A mixed full-sib/half-sib design was applied for the field strain and a full-sib design for the laboratory strain. The heritability of total distance was 0.57 for the field strain and 0.37 for the laboratory strain (both sexes). In addition, a heritability of 0.38 for total distance was estimated by parent-offspring regression for the laboratory strain. All three values were significantly different from zero P<0.05 and show that there is a significant additive genetic influence on flight capacity.The genetic correlations between total distance and other flight traits (total duration, flight velocity, longest flight) were between 0.84 and 1.00 for both strains and suggest that these traits actually belong to a single one. High genetic correlations were also found between total distance and the morphological traits body weight and wing length for the field strain, whereas a negative correlation was found between total flight distance and body weight for the laboratory strain. This difference between the two strains was interpreted as a possible trade-off between flight capacity and fecundity.     

Flight-oogenesis syndrome in a blood-sucking bug: biochemical aspects of lipid metabolism

Lipophorin (Lp), either labeled in diacylglycerol moiety with [(3)H]-Palmitic acid or in phospholipid moiety with (32)Pi, was injected into Rhodnius prolixus females. Insects were induced to flight for different times. In just a few minutes of flight, the transfer of radioactivity to ovaries decreased, accompanied by its increase to flight muscles. After one hour of flight, Lp density was higher (1.132 g/mL) than before flight (1.116 g/mL). Lp purified from insects after flight was analyzed by gel filtration chromatography and a polyacrylamide gel pore limit electrophoresis. Both analyses demonstrated a decrease in Lp molecular mass after flight but no changes in apoLp-III amounts were observed. Time-course experiments showed that only 30 min of flight are required for the detection of changes in Lp density and molecular mass. About the same time of rest is necessary for Lp density and molecular mass to return to the baseline value. The lipid content from Lp particles, determined by high-performance thin-layer chromatography (HPTLC), showed a decrease in total lipids after flight. At the same time, an increase of many classes of lipids was observed in flight muscles except for triacylglycerol, which was reduced. The increase of flight muscle lipids was accompanied by a decrease of the ovaries lipid content. The insects subjected to daily exhaustive flight showed a significant decrease in total number of eggs produced. But insects subjected to a single exhaustive flight showed only a small reduction in total number of eggs. Lp density variation during the flight activity of Rhodnius prolixus females is discussed in association with physiological events such as oogenesis.     

甘蓝夜蛾Mamestra brassicae Linnaeus飞行能力研究

【目的】测定日龄、性别、交配等因素对农业迁飞性害虫甘蓝夜蛾Mamestra brassicae Linnaeus飞行能力的影响,为其迁飞行为研究和异地测报提供理论依据。【方法】在气温为(24±1)℃、相对湿度为75%±5%的实验室环境下,利用飞行磨系统对甘蓝夜蛾实验室种群1~5日龄未交配个体、已交配的3日龄个体以及野外迁飞种群分别进行连续24 h吊飞测试,记录其累计飞行时间、累计飞行距离、平均飞行速率等参数。【结果】甘蓝夜蛾实验室种群的飞行能力随日龄增长而变化,初羽化时即具有较强的飞行能力,2~3日龄达到峰值,4~5日龄的飞行能力显著下降;雌性甘蓝夜蛾的飞行能力强于雄性甘蓝夜蛾;交配的甘蓝夜蛾平均飞行速率显著小于处女甘蓝夜蛾,但二者的平均飞行时间和飞行距离均无显著差异。此外,渤海湾迁飞种群中晚季节南迁种群的飞行能力显著强于早季节北迁种群和过渡种群。【结论】日龄和交配状态是影响甘蓝夜蛾飞行能力的关键因素。     

稻纵卷叶螟的飞行和再迁飞能力

稻纵卷叶螟Cnaphalocrocis medinalis (Guenée)可以通过连续几夜的飞行实现远距离迁移, 这种变幻莫测的再迁飞能力给稻纵卷叶螟的预测造成了极大的困难, 明确其迁飞行为参数是灾变预警的前提。为此, 利用飞行磨装置测定了稻纵卷叶螟成虫的飞行能力和再迁飞能力。结果表明: 在生殖隔离条件下, 稻纵卷叶螟不同日龄和不同性别的成虫的飞行能力间没有显著差异, 雌雄虫的平均飞行时间分别为156.94±103.19 min和147.71±111.38 min。根据吊飞的累计飞行时间(accumulative flight duration, AFD)可将稻纵卷叶螟种群划分为居留型(AFD<40 min)、迁飞型(40 min≤AFD≤130 min)和强迁飞型(AFD>130 min) 3种类型; 且3种类型的个体比率分别为46.1%, 27.3%和26.6%, 其中居留型平均累计飞行时间为11 min, 迁飞型为82 min, 强迁飞型为232 min。稻纵卷叶螟具有很强的再迁飞能力, 其种群作一次迁飞的个体比率都大于90%, 2次(夜)再迁飞的比率达70%以上, 一般可进行4~5次(夜)再迁飞, 最多可达9次(夜)。成虫的补充营养对再迁飞能力没有显著影响, 但蜜水可增强成虫的飞行能力。这些研究结果为稻纵卷叶螟的虫源分析和迁入区预测提供了基本参数。     

保幼激素类似物对粘虫飞行能力及能源物质含量的调控(英文)

本文报道了保幼激素类似物methoprene(JHM)对粘虫Mythimnaseparata(Walker)飞行能力及飞行能源物质含量的影响。总体而言 ,用JHM (30 μg/蛾 )处理过的成虫飞行能力比对照 (丙酮处理 )的弱 ,但因性别及处理后的时间变化而异 :处理雌蛾的飞行能力在处理后的 1d到 3d与对照没有显著差异 ,但在4d到 6d则显著低于对照 ;处理雄蛾的飞行能力一直比对照的强 ,尽管差异不显著。处理过的雌蛾飞行个体比对照的少 ,而处理过的雄蛾比对照的多。究其原因 ,主要是JHM处理过的雌蛾甘油酯含量在处理后的 3d后明显下降 ,而处理过的雄蛾甘油酯含量一直比对照的高。但无论是雌蛾还是雄蛾 ,处理的与对照的糖元含量均没有明显的差异。这些结果表明 ,作用于成虫体内甘油酯含量是保幼激素影响粘虫飞行能力的主要原因之一。最后 ,对保幼激素影响粘虫飞行能力的其它可能原因也进行了讨论     

REGULATION OF FLIGHT CAPACITY AND CONTENTS OF ENERGY SUBSTANCES BY METHOPRENE IN THE MOTHS OF ORIENTAL ARMYWORM,MYTHIMNA SEPARATA*

Abstract The flight capacity and contents of energy substances in the moths of migratory Oriental armyworm, Mythimna separata (Walker)dosed with juvenile hormone analogue methoprene(JHM) were compared with the normal moth through day‐1 to day‐6 after the treatment. The flight capacity of JHM‐treated moths, as determined by a 12‐hours tethered‐flight test, was significantly lower than that of the controls, although it might differ with their age and sex. The moth's flight capacity between the treatments was insignificantly different from the first to 3rd day after the treatment but was significantly different from the 4th to 6th day either in the mean flight duration or in distance. Evaluation of the long fliers at the same stages between the treatments also supported this finding. Flight capacity of the JHM‐treated moths also differed with the sex. The JHM‐treated female did not fly less than the control from day‐1 to day‐3, but did significantly less from day‐4 to day‐6 after the treatment. The flight capacity of the JHM‐treated males, however, was not weaker than that of the control throughout the test period. Comparison of the levels of energy substances in the JHM‐treated adults and the controls showed that JHM may directly acted on metabolism of glyceride, which in turn affected flight capacity. Furthermore, higher levels of glyceride in the treated male adults raised their flight capacity to a stronger levels than the control in most of the days of tethered‐flight test period. Contents of glycogen, however, were insignificantly affected by JHM in both male and female adults. In might therefore be concluded that levels of JH is a critical factor regulationg migratory behavior in the army worm moth. In addition to affect metabolism of glyceride, other possible physiological roles that JH played in determining migrattory behavior are also discussed.     

枣实蝇成虫飞行能力的测定

【目的】为了明确枣实蝇Carpomya vesuviana Costa成虫飞行扩散能力及相关因子对其飞行能力的影响。【方法】本研究以SUN-FL型智能昆虫飞行信息系统（飞行磨）吊飞方法, 测定了不同日龄、性别的枣实蝇成虫的飞行能力, 并探究了温度对枣实蝇飞行能力的影响。【结果】羽化后12 d左右的枣实蝇飞行能力最强, 雌虫平均飞行距离和最远飞行距离分别为1.037和3.192 km, 雄虫分别为0.943和3.085 km; 枣实蝇飞行能力随着日龄的增加呈现先增强后减弱的趋势; 相同日龄的雌成虫平均飞行距离、平均飞行时间略高于雄虫, 雌、雄虫的平均飞行距离、平均最快飞行速度、平均飞行时间之间没有显著性差异; 环境温度28～34℃为枣实蝇最佳飞行温度区间, 且31℃条件下飞行能力最强。【结论】由此可见, 枣实蝇成虫具有较强的迁飞扩散能力。     

粘虫幼虫密度对成虫飞行与生殖的影响

本文报道了不同幼虫密度下(1、10、20、30、40头/瓶-850m1)粘虫蛾飞行能力与产卵量的变化情况。对未取食1日龄成虫12h飞行能力的测定结果表明,不同幼虫密度羽化的成虫飞行力差异显著(P<0.05),其中以10头/瓶羽化的成虫飞行时间最长(平均225.4分),飞行距离最远(平均17.5km),飞行超过120min的个体为61.1%,超过10 km的为55%。其它处理的各项参数随幼虫密度的增加而下降。粘虫蛾的翅长、翅宽、翅面积和翅负荷随幼虫密度的增加而下降。除翊负荷外,其余各项参数在处理间的差异显著(P<0.05)。成虫飞行能力与蛹重或翅负荷不呈直线相关,但与蛹重具有一定的关系：当蛹重为300-400mg时, 强飞行个体均超过50%, 当小于300mg或大于400mg时,强飞行个体比例下降,当小于225mg时,强飞行个体为零。处理间的成虫产卵量差异显著(P<0.05),且随幼虫密度的增加而下降。密度内的蛹重与成虫产卵量的关系不明显,但密度间的蛹重与产卵量的关系高度相关(r=0.78,P<0.01)。这些结果表明,当粘虫幼虫密度达到一定的阈值时,便可能促使成虫迁飞,而不是等到种群密度很高时才进行迁飞。     

白背飞虱的再迁飞能力

通过室内模拟试验研究了白背飞虱经过一次远迁降落、取食不同水稻品种后的再迁飞能力。根据吊飞试验的持续飞行时间可将白背飞虱种群划分为居留型(<30 min)、迁飞型(≥30 min)、远迁型(>420 min)和再迁飞型(第二次吊飞持续飞行时间 ≥30 min)。在所测的558头白背飞虱中,再迁飞型的比率为5.7%;而在112头迁飞型个体中,再迁飞的比率为28.6%。取食不同品种的水稻对白背飞虱的飞行能力和再迁飞能力有显著影响。取食感虫水稻的白背飞虱飞行能力和再迁飞能力较强,再迁飞的比率也较高 (>5%)。吊飞前后取食常规稻与耐虫品种组合的飞虱的再迁飞时间则较短,再迁飞比率也较低;但吊飞前后均以耐虫品种饲喂的个体,反而也表现出较高的再迁飞比率和中等水平的再迁飞时间。而且,第一次飞行360 min以上的个体具有较强的再迁飞潜力。交配只对6日龄雌虫和2日龄雄虫的飞行能力有显著影响。     

南京地区棉蚜的飞行活动节律及其飞行能力

昆虫的飞行活动规律及飞行能力是研究其能否迁飞的基础。通过采用春季到秋季20 m高空黄盆诱蚜、高空所诱蚜和春季木槿树上有翅蚜的卵巢解剖,以及春夏秋三季田间有翅蚜的吊飞试验等方法,研究了南京地区棉蚜Aphis gossypii的飞行活动节律和飞行能力。结果表明,有翅棉蚜的日羽化高峰出现在19:00～20:00。2001年南京地区棉蚜的春、秋两季迁飞高峰分别在5月8日和10月25日。5月份高空诱集的棉蚜中,95.7%个体的卵巢小管数在7条以下,而木槿上羽化后1天的有翅蚜中有35.2%个体的卵巢小管数在7条以上;高空诱蚜和木槿上蚜的平均卵巢小管数存在极显著差异,分别为3.94±1.65和5.88±1.92。8月中下旬棉田棉蚜存在低空飞行行为,并且出现飞行高峰时有翅蚜的卵巢小管数平均在6条以下,超过6条则停止飞行。羽化后1～2天有翅棉蚜吊飞个体的飞行比率和平均飞行距离表现为春、秋季显著大于夏季,三季的最长飞行距离分别为3.89 km、6.15 km和1.44 km。     

Heritability of flight and resting metabolic rates in the Glanville fritillary butterfly

Dispersal capacity is a key life‐history trait especially in species inhabiting fragmented landscapes. Evolutionary models predict that, given sufficient heritable variation, dispersal rate responds to natural selection imposed by habitat loss and fragmentation. Here, we estimate phenotypic variance components and heritability of flight and resting metabolic rates (RMRs) in an ecological model species, the Glanville fritillary butterfly, in which flight metabolic rate (FMR) is known to correlate strongly with dispersal rate. We modelled a two‐generation pedigree with the animal model to distinguish additive genetic variance from maternal and common environmental effects. The results show that FMR is significantly heritable, with additive genetic variance accounting for about 40% of total phenotypic variance; thus, FMR has the potential to respond to selection on dispersal capacity. Maternal influences on flight metabolism were negligible. Heritability of flight metabolism was context dependent, as in stressful thermal conditions, environmentally induced variation dominated over additive genetic effects. There was no heritability in RMR, which was instead strongly influenced by maternal effects. This study contributes to a mechanistic understanding of the evolution of dispersal‐related traits, a pressing question in view of the challenges posed to many species by changing climate and fragmentation of natural habitats.     

温度对甜菜夜蛾飞行能力的影响

温度对甜菜夜蛾飞行能力有显著的影响（P<0.05）。在16～32℃内,成虫均能进行正常的飞行活动。24℃下的成虫飞行能力最强,在15 h的吊飞飞行中,成虫飞行距离最远（37.14 km）、飞行速度最快（0.87 m/s）、飞行时间最长（11.73 h）。温度低于２０℃或高于２８℃时,其飞行能力均显著降低。甜菜夜蛾在不同温度下飞行时对主要能源物质（甘油三酯）的利用效率不同。在较适宜的温度下,尽管成虫飞行消耗的甘油三酯较多,但单位飞行距离所消耗的甘油三酯却较少,即利用效率较高,表明成虫飞行能源物质利用效率的不同是导致其在不同温度下飞行能力产生差异的主要原因之一。     

Long flights in Cydia pomonella L. (Lepidoptera: Tortricidae) measured by a flight mill: influence of sex, mated status and age

Abstract. The flight capacity of Cydia pomonella L. (Lepidoptera: Tortricidae) was measured in the laboratory by using computer-linked flight mills. Codling moths showed a large variation in flight capacity between individuals. We defined arbitrarily a longest single flight (LSF) of more than 5 km as an index for long-flyers. About 16.7% of virgin and 10.0% of mated males and 20.0% of virgin and 7.4% of mated females undertook such flights. Based on the LSF and the total distance flown (TDF^we concluded that males and females have little or no difference in flight capacity and that both the within-and between-habitat flights are similar in number and magnitude for both sexes. In the field, females are therefore potentially able to undertake flights of up to 11 km, as reported for males by other authors. This ability was highest at ages of 2–7 days after emergence, i.e. the first third of their lifetime, for virgin and mated male moths and for virgin female moths. Mated females showed peak flight capacity between 1 and 3 days after eclosion, which corresponded with the major egg-laying period. Few long flights were undertaken before oviposition. These findings do not agree with the oogenesis flight syndrome described by other authors, and this theory is believed not to apply to C.pomonella. Our laboratory results are discussed in relation to field experiments in general and hypotheses are developed about the significance of long-flyers for this species.     

The migration syndrome in the African armyworm moth, Spodoptera exempts: allocation of resources to flight and reproduction

Abstract. Selection for the capacity for prolonged tethered flight in Spodoptera exempta resulted in heavier moths, with significantly larger abdominal glyceride glycerol contents in females of two flight-selected strains (87% and 49% higher than in the comparable non-selected strain) and in males of one of them (80% higher). All flight-selected strains contained individuals of both sexes with very high abdominal glyceride levels. There was no significant relationship between abdominal total glyceride glycerol after flight and flight duration for non-selected moths, but an inverse linear relationship was evident in both sexes from a flight-selected strain. Oxygen consumption during tethered flights by flight-selected moths ranged from 28.2 to 56.6 ml O₂g^-1h^-1.
Using these and previous data, notional energy budgets were calculated to account for flight, reproduction and resting metabolism for non-selected and flight-selected S. exempta flown on the flight balances and provided thereafter with distilled water. The results confirm the trade-off between flight and reproduction reported by Gunn et al. (1989). A similar approach using data for two non-selected strains from the field in Kenya indicated genetic variation in migratory potential, reflected both in pre-reproductive period and resources available for flight. We conclude that elevated glyceride levels are a component of the migratory syndrome in S. exempta and that this is the major factor underlying the curvilinear relationship between flight duration and fecundity obtained by Gunn et al. (1989).