Cryptic female choice predicated on wing dimorphism in decorated crickets

Male decorated crickets, Gryttodes sigllatus, normally lackbind wings and are incapable of flight (short-winged males),but occasionally exhibit fully developed hind wings that makerudimentary flight possible (long-winged males). Long-wingedmales bear a cost of flight in the form of decreased inseminationsuccess, which arises as a consequence of two interrelated factors:(1) long-winged males exhibit a lower reproductive investmentrelative to short-winged males, as measured by the mass of amale's spermatophore and reproductive organs and (2) the postcopulatorybehavior of females favors males that maximize their reproductiveinvestment. Of particular importance to male mating successis the spermatophylax, a large gelatinous mass forming partof the spermatophore and consumed by the female after mating.Consumption of the spermatophylax keeps the female preoccupiedwhile sperm are discharged from the remaining portion of thespermatophore (sperm ampulla) into her repro ductive tract.The spermatophylax of long-winged males is significantly smallerthan that of short-winged males and consequently requires lesstime to consume. As a result, the sperm ampulla of long-wingedmales is frequently removed before its complete evacuation andsignificantly sooner than that of short-winged males. Becausethe spermatophore-removal behavior of females mediates the relativeinsemination success of short-winged and long-winged males,it can be considered a form of cryptic female choice     

Sexual dimorphism inAnastrepha suspensa (Loew) and other tephritid fruit flies (Diptera: Tephritidae): Possible roles of developmental rate,fecundity, and dispersal

Larger male Caribbean fruit flies are more likely to be chosen as mates and defeat rivals in territorial contests. Yet males are smaller than females. Adaptive explanations for relatively small male size include (1) acceleration of male development to maximize female encounter rates, (2) selection for greater female size to increase fecundity, and (3) selection for body sizes most suitable for sexually dimorphic degrees of mobility, speed, and distance flight. None of these unambiguously accounts for the degree of sexual dimorphism. Male development is not accelerated relative to that of females. On average, males remain inside fruit longer than females and those males with extended development periods are smaller than more rapidly developing individuals. There is no evidence that female enlargement alone, presumably for greater fecundity, has generated the degree of dimorphism in the Caribbean fruit fly or other fruit flies. The relationship between dimorphism and mean female body size in 27 species of Tephritidae is the opposite of what would be predicted if differences in dimorphism were due to differences in unilateral female enlargement. Larger size in a species or in one sex of a species may be an adaptation for extensive flight. In general, among 32 species of fruit flies, as body size increases, wing shape becomes progressively more suited for distance flight. However, there are important exceptions to this correlation. Both sexual selection and nonadaptive allometries may contribute to the range of dimorphisms within the family.     

Influences of sex, size, and symmetry on ejaculate expenditure in a moth

Although sperm fundamentally function to fertilize eggs, forcesarising from both sexes select for optimal ejaculate composition.Sperm competition is one recognized agent in the evolution ofsperm and ejaculate structure. Few studies, however, have examinedhow female factors influence ejaculate structure, despite somebehavioral evidence for male mate choice. Male Plodia interpunctella(Lepidoptera, Pyralidae) accrue all resources for reproductionas larvae. Adults emerge with a limited sperm complement andare therefore under intense selection to optimize gamete allocation.I detected no effect of male body weight on ejaculate size.However, female reproductive potential (ovary masses) was dictatedby body weight In addition, heavier females had greater spermathecalvolumes, but there was no such relationship with bursal size.Finally, heavier females showed a higher mating frequency. Ifound that mating males were sensitive to female size and producedlarger ejaculates when mating with heavier females. Males mayejaculate more sperm into larger females either because it paysthem to "spend" more reproductive resources on matings thatprovide greater reproductive potential, or because heavier (longerlived and more attractive) females mate more frequently andhave larger spermathecal volumes. Alternatively, females maycontrol spermatophore formation and "accept" an appropriateejaculate to maximize fertility. Males may therefore be alsoselected to ejaculate more sperm into larger females to counteractgreater risks of sperm competition associated with heavier females.There was no association between male or female femur asymmetryand ejaculate size. P.interpunctella may be selected to exercisemodulation of ejaculate size because males invest paternally,sperm for the single reproductive episode are limited, and femalefecundity and mating pattern vary between individuals and areassociated with body weight. More obvious variability in malereproductive behavior and choice may therefore be paralleledat the cryptic gametic level by plasticity in ejaculate allocation.     

Orientation of Fall-migrating Butterflies in North Peninsular Florida and Source Areas

Phoebis sennae (Pieridae), Agraulis vanillae (Heliconidae) and Urbanus proteus (Hesperiidae) migrate into peninsular Florida each fall from summer breeding areas throughout the south-eastern United States. Fall flight directions of the three species were studied at 78 sites for clues to their means of orientation and migratory routes. Mean flight directions for a visit to a site were calculated using conventional circular statistics. The distribution of flight directions permitted using linear procedures to combine visit means. The overall mean direction (OMD) of a species at a site was defined as the mean of visit means, weighted by frequency/angular variance, with a lower limit of 0.2 imposed on angular variance. In intensive studies at two sites at Gainesville, Florida, mean flight directions during fall migration were largely independent of time of day and crosswinds. The OMDs of the three species at the two Gainesville sites were similar (142 to 156°) and not significantly different among species at a site or, for the same group of dates, between sites for a species. However, day-to-day variation among species and between sites was not concordant. Visits to 65 sites on a grid throughout the southeastern United States and to 11 sites along transects inland from the Gulf and Atlantic coasts yielded 10 cases of a P. sennae OMD at a grid or transect site differing significantly from its OMD at the main Gainesville site. In each of these, the OMD was more easterly at sites inland from the Gulf coast or more southerly or south-westerly at sites inland from the Atlantic coast. By unknown means and with large, unexplained day-to-day variations in directions, P. sennae converge on peninsular Florida from widespread summer breeding grounds. They do this without closely following the Atlantic or Gulf coasts.     

Allometry and proximate mechanisms of sexual selection in photinus fireflies, and some other beetles

Ever since Darwin identified it as the force responsible forthe evolution of exaggerated male characters, sexual selectionhas been the focus of research aimed at understanding the mostbizarre and intriguing morphologies and behaviors in Nature.Two congeneric species in the firefly genus Photinus, P. pyralisand P. macdermotti, afford a unique opportunity to examine theinteraction between sexual and countervailing natural selectionthat act to shape the evolution of mating behavior and bodysize in closely related species with very different courtshipstrategies. Photinus pyralis males emit very bright flashesduring their extended patrolling flights and form ‘loveknots’ of competing suitors, while P. macdermotti males,whose courtships seldom exceed two competing males, produceweaker flashes during a shorter patrolling period. Possibly as a consequence of their scramble competition andlong flights, not only is there an extremely wide range of bodysizes in P. pyralis males, but they also exhibit wing allometricslopes greater than one, and lantern allometries less than one.In contrast, P. macdermotti males do not have allometric slopessignificantly different from one. Small males, when tested inan artificial scramble situation move faster than large males,an advantage in the intense competition that ensues once a femaleis located. Females answer several males in alternation andfail to respond to all male flashes, with the evident consequencethat love knots frequently develop around such fickle females.Allometric relationships in two non-luminescent beetle specieswith non-visual courtship protocols are compared. Visual, sexuallyselected characters showed positive allometric slopes, whilenon-visual characters showed isometry or negative slopes. Datapresented here support the existence of distinct patterns inmodality-specific sexual selection.     

Female preference for male courtship flashes in Photinus ignitus fireflies

In Photinus fireflies, males produce spontaneous bioluminescentcourtship flashes. Females preferentially respond to particularmale flashes with flashes of their own. This study exploredvariation in female flash responsiveness as a function of maleflash duration, female condition, lantern size, and lanterndistance, as well as the relationship between male characteristicsand spermatophore mass in Photinus ignitus fireflies. We determinedfemale preference by scoring female flash response to simulatedmale flashes and determined variation in overall female flashresponsiveness for laboratory-mated, laboratory-fed, and controlP. ignitus females. Flash duration, lantern size, and body masswere recorded for field-collected males. Males were then matedto determine spermatophore mass. Females exhibited greater preferencefor artificial flashes representing the upper range of conspecificmale flash duration and lantern size as well as flashes producedat a closer distance. Both laboratory-mated and laboratory-fedP. ignitus females showed lower overall responsiveness acrossall flash durations relative to control females that did notmate or feed in the laboratory. Male flash duration predicteda significant proportion of the variation in spermatophore massfor early-season males. These results suggest that female Photinusignitus may prefer long flashes in order to obtain the directbenefit of larger spermatophores and may adjust their overallflash responsiveness as the relative importance of this benefitvarieswith changing female condition.     

Sex and social costs of escaping in the striped plateau lizard Sceloporus virgatus

As a predator approaches, prey base decisions about when toflee on a balance between degree of predation risk and costsof escaping. Lost opportunities to perform activities that mayincrease fitness are major escape costs. Paramount among theseare chances to increase fitness by courting and mating and bydriving away sexual rivals. Because sexual selection imposesdifferent social demands on the sexes, social opportunitiescan have different consequences for males and females, but effectsof sex differences in social opportunity costs on escape behaviorare unknown. We conducted a field experiment showing that malestriped plateau lizards (Sceloporus virgatus) given the opportunityto court or perform aggressive behavior permit closer approachbefore fleeing, but females do not. Males allowed a simulatedpredator to approach closer before initiating escape if a tetheredmale or female rather than a control stimulus was introducedto them, but females initiated escape at similar distances inall conditions. For males, a trade-off between the greater predationrisk accepted before fleeing due to the likelihood of enhancingfitness by sexual or aggressive behavior accounts for closerapproach allowed in the presence of conspecifics. Mating opportunitiesare not limiting for females in most species and females oftenhave little to gain by interacting aggressively with other females.Therefore, presence of a conspecific male or female may notjustify taking greater risk. Results confirm the predictionof optimal escape theory that flight initiation decreases ascost of escaping increases. The sex difference in effect ofpresence of conspecifics on flight initiation distance is aconsequence of the sex difference in costs of escaping.     

Environmental heterogeneity and alternative mating tactics in the damselfly Protoneura amatoria

Conditional male mating strategies have been studied extensivelyin relation to male attributes, such as size and resource-holdingpotential, but few studies have considered the effects of environmentalheterogeneity on the use of alternative mating tactics. In somesystems, environmental heterogeneity may be the key to understandingthe evolution and maintenance of such polyphenisms. I examinedthe influence of the physical environment on the use of alternativetactics by the damselfly Protoneura amatoria. Male P. amatoriareversibly use 2 tactics to gain matings: 1) sit and wait inthe canopy for passing females or 2) hover over the water andattempt to grab females that are ovipositing in floating debris.Observations in 3 streams indicated that the use of the hoveringtactic was greater under high-light than low-light conditionsand at higher densities of ovipositing females. The densityof ovipositing females was correlated with both the light conditionsand the availability of oviposition substrate, indicating thatphysical factors exert indirect as well as direct influenceson tactic use. Experimental manipulations showed that both malesand females responded directly to light conditions and suggestedthat males responded directly to the density of ovipositingfemales. These results can be explained largely in terms ofthe cues and constraints inherent in different light environments.Thus, the conditional mating strategy of P. amatoria appearsto have evolved in response to, and been maintained by, fine-scalevariation in the physical environment. These findings are discussedin relation to flight dynamics and predation risk.     

Optimal strategies for insects migrating in the flight boundary layer: mechanisms and consequences

Directed aerial displacement requires that a volant organism'sairspeed exceeds ambient wind speed. For biologically relevantaltitudes, wind speed increases exponentially with increasedheight above the ground. Thus, dispersal of most insects isinfluenced by atmospheric conditions. However, insects thatfly close to the Earth's surface displace within the flightboundary layer where insect airspeeds are relatively high. Overthe past 17 years, we have studied boundary-layer insects byfollowing individuals as they migrate across the Caribbean Seaand the Panama Canal. Although most migrants evade either droughtor cold, nymphalid and pierid butterflies migrate across Panamanear the onset of the rainy season. Dragonflies of the genusPantala migrate in October concurrently with frontal weathersystems. Migrating the furthest and thereby being the most difficultto study, the diurnal moth Urania fulgens migrates between Centraland South America. Migratory butterflies and dragonflies arecapable of directed movement towards a preferred compass directionin variable winds, whereas the moths drift with winds over water.Butterflies orient using both global and local cues. Consistentwith optimal migration theory, butterflies and dragonflies adjusttheir flight speeds in ways that maximize migratory distancetraveled per unit fuel, whereas the moths do not. Moreover,only butterflies adjust their flight speed in relation to endogenousfat reserves. It is likely that these insects use optic flowto gauge their speed and drift, and thus must migrate wheresufficient detail in the Earth's surface is visible to them.The abilities of butterflies and dragonflies to adjust theirairspeed over water indicate sophisticated control and guidancesystems pertaining to migration.     

Differential allocation of male-derived nutrients in two lampyrid beetles with contrasting life-history characteristics

Across diverse animal taxa, sperm is transferred from malesto females during mating within a spermatophore produced bymale accessory glands. In some insects, male spermatophoresprovide females with nutrients that may be used to increasereproductive output or for somatic maintenance, while in othersno such benefits have been detected. Boggs suggested that variationin the current function of spermatophores may be explained byconsidering ecological and life-history factors. This studyexamined spermatophore function in Ellychnia corrusca and Photinusignitus (Coleoptera: Lampyridae), two beetles that exhibit markeddifferences in adult diet, adult life span, and overwinteringstage. During mating, males of both species transfer to femalesa complex, proteinaceous spermatophore, which is subsequentlydigested in a specialized sac within the female reproductive tract.Males of each species were injected with ³H-radiolabeled aminoacid mixtures and mated with conspecific females. The fate of spermatophore-derivedproteins was determined by dissecting females at various timesafter mating with these radiolabeled males. Females of thesetwo species showed markedly different patterns of incorporationof spermatophorederived nutrients. P. ignitus females incorporatedthe majority (62%) of spermatophore-derived protein into maturingoocytes within 2 days after mating. In contrast, in E. corruscaa large percentage of radiolabel (46%) appeared in female fatbody at 6 days after mating, with a threefold lower allocationto maturing oocytes compared to P. ignitus. These findings supportthe prediction that short-lived, nonfeeding females are selectedto allocate a greater proportion of male-derived nutrients toreproduction, while longer-lived, feeding females are selectedto allocate a greater proportion to somatic reserves and maintenance.These results suggest that life-history characteristics maybe useful in explaining observed differences in spermatophorefunction across taxa.     

Preference polymorphism for coloration but no speciation in a population of Lake Victoria cichlids

Female mating preference based on male nuptial coloration hasbeen suggested to be an important source of diversifying selectionin the radiation of Lake Victoria cichlid fish. Initial variationin female preference is a prerequisite for diversifying selection;however, it is rarely studied in natural populations. In clearwater areas of Lake Victoria, the sibling species Pundamiliapundamilia with blue males and Pundamilia nyererei with redmales coexist, intermediate phenotypes are rare, and most femaleshave species-assortative mating preferences. Here, we studya population of Pundamilia that inhabits turbid water wheremale coloration is variable from reddish to blue with most malesintermediate. We investigated male phenotype distribution andfemale mating preferences. Male phenotype was unimodally distributedwith a mode on intermediate color in 1 year and more blue-shiftedin 2 other years. In mate choice experiments with females ofthe turbid water population and males from a clearer water population,we found females with a significant and consistent preferencefor P. pundamilia (blue) males, females with such preferencesfor P. nyererei (red) males, and many females without a preference.Hence, female mating preferences in this population could causedisruptive selection on male coloration that is probably constrainedby the low signal transduction of the turbid water environment.We suggest that if environmental signal transduction was improvedand the preference/color polymorphism was stabilized by negativefrequency-dependent selection, divergent sexual selection mightseparate the 2 morphs into reproductively isolated species resemblingthe clear water species P. pundamilia and P. nyererei.     

Effect of Eyestalk-Ablation on Circulating Ecdysteroids in Hemolymph of Snow Crabs, Chionoecetes opilio: Physiological Evidence for a Terminal Molt

Bering Sea snow crabs (Chionoecetes opilio) are a commerciallyimportant crab harvested in the Bering Sea. Optimal managementof this species requires an understanding of the biology ofthis crab that is currently incomplete. Fisheries managers applya continuous growth model in their management of snow crab,which assumes that male crabs increase in size throughout theirlifespan. Male snow crabs undergo a morphometric molt that leadsto a disproportionate increase in chelae size and it is stilldebated whether this molt is associated with a terminal molt.This study was conducted to determine whether adult male C.opilio are anecdysic. Using current knowledge of the hormonalregulation of crustacean growth, snow crab physiology was manipulatedto induce an increase in molting hormones (ecdysteroids). Sincefemale snow crabs are known to undergo a terminal molt afterattaining reproductive maturity, we compared ecdysteroid levelsin eyestalk-ablated terminally molted females, small-clawedmales and large-clawed males. Snow crabs were collected fromthe Bering Sea and maintained in circulating seawater at approximately6°C. Animals were either eyestalk-ablated or left intact.Ecdysteroid levels in hemolymph were quantified using an enzyme-linkedimmunosorbant assay (ELISA). Circulating ecdysteroids were significantlyhigher in small-clawed male crabs when compared to large-clawedmales or terminally molted females. Eyestalk-ablation increasedcirculating ecdysteroids in small-clawed males, but had no significanteffect on circulating ecdysteroids in large-clawed males orin terminally molted females.     

Territoriality and song as flexible paternity guards in dunnocks and alpine accentors

I compare paternity defense strategies in the variable matingsystems of alpine accentors Prunella collaris and dunnocks P.modularis. I show that in dunnocks breeding territoriality functionsexclusively for mate defense. Male investment in territorialityincreases with the number of females they are defending, andwhen females are removed males sharply decrease their song outputand eventually abandon their territories. Further, I show thatpaternity defense strategies vary in relation to group composition.In single-male groups there is greater investment in territorialdefense and less investment in mate guarding during the femalefertile period than in multimale groups. I discuss the influenceof the contrasting habitats of dunnocks and alpine accentorson their paternity defense strategies.     

Comparative paternal and infanticidal behavior of sympatric white-footed mice (Peromyscus leucopus noveboracensis) and deermice (P. maniculatus nubiterrae)

We studied parental and infanticidal behavior in the field andlaboratory in two ecologically equivalent and sympatric congeners,white-footed mice, Peromyscus leucopus noveboracensis, and deermice,P. maniculatus nubiterrae. Despite their close phylogeneticrelationship and ecological similarity, various aspects of parentaland nesting behavior of the two species were significantly different.P. maniculatus males were more paternal than were P. leucopusmales in that they retrieved pups, nested with pregnant femalesand females with newborn pups, and formed longer associationswith females than did P. leucopus males. Thus, P. m. nubiterraeexhibited more pair-bonding (monogamous) characteristics thandid either P. leucopus or P. m. bairdi, as reported in otherstudies. The behavioral differences may represent the differentevolutionary history of the three subspecies. Infanticidal behavior,however, was similar in both species. Dispersing and unmatedmales killed strange pups placed in experimental test chambersin the field, whereas mated males did not kill pups within theirown home ranges. Resident females of both species were moreinfanticidal than were males, killing pups in 90% of the trials.The results support the sexual selection and resource competitionhypotheses for male and female infanticide, respectively. [BehavEcol 1991; 2: 38-45]     

Female egg dumping and the effect of sex ratio on male egg carrying in a coreid bug

Phyllomorpha laciniata Vill (Heteroptera, Coreidae) is uniqueamong terrestrial insects in that females glue eggs on the backsof other conspecifics. Egg carrying byP. laciniatamales haspreviously been considered as paternal care. We explored femaleoviposition with respect to previous mating experience of femalesand tested whether sex ratio affects male egg-carrying. Thehypothesis that male egg-carrying is a form of paternal carepredicts that a male should always accept eggs after matingwith a female. However, if male egg-carrying is a form of postcopulatorymate guarding rather than paternal care, egg carrying shouldincrease in the presence of other males. When two couples wereplaced together, females laid eggs on the backs of all individualsenclosed, including the backs of other females. However, whena female was accompanied by 2 males, 22 out of 26 females ovipositedon their mating partner. Thus, sexual competition rather thanpaternity alone, affects a male's eagerness to carry eggs. However,even if males sometimes carry their own eggs, females lay eggson the backs of all conspecifics they can easily acquire. Thus,egg carrying in P. laciniata is partially voluntary and partiallythe result of female egg dumping     

NORTH ATLANTIC NUDIBRANCHS OF THE CHROMODORTS CLENCHI COLOUR GROUP (OPISTHOBRANCHIA: CHROMODORIDIDAE)

The correct identity of three chromodorid nudibranch species,Chromodoris clenchi, C. neona and C. binza is established onthe basis of material from the Caribbean Sea. These three speciesare compared with C. britoi, from the northeastern Atlanticand the Mediterranean Sea. All four species have a colour patternof cream with red (or yellow) lines and blue spots. (Received 30 March 1993; accepted 20 November 1993)     

Nectar uptake rates and optimal nectar concentrations of two butterfly species

Summary The relationship between sucrose concentration of nectar and volume uptake rate by the butterflies Agraulis vanillae (Nymphalidae) and Phoebis sennae (Pieridae) was examined. Recent theoretical models simulating feeding energetics of nectarivores have assumed that this volume uptake rate is produced by a constant but undetermined pressure drop (the difference between pressure at the proximal and distal ends of the feeding channel) at all nectar concentrations. These models predict that nectar of 20–25% sucrose maximizes the rate of energy intake and should thus be preferred by nectarivores. Data collected for Agraulis and Phoebis falsify this pressure drop assumption; both species produce greater pressure drops with increasing nectar concentration. In addition, males of both species produce greater suction pressure and uptake rates than females. This results in greater rates of energy intake for males of both species. The volume uptake rates produced by each species differ from those predicted by the models. This produces a maximal rate of energy intake at 35–40% sucrose rather than 20–25%. The empirically determined relationship between energy intake rate and nectar concentration esembles that predicted for discontinuous nectar feeders such as hummingbirds more closely than the relationship predicted for continuous suction feeders, suggesting that other basic assumptions about the feeding mechanism of butterflies should be critically examined.     

Male tactics and reproductive success in the harem polygynous bat Saccopteryx bilineata

Alternative tactics in reproductive behavior enable individualsto maximize their fitness in relation to competitors in thesame population. In many taxa, territoriality is a common tacticof males to increase their reproductive success. In the batSaccopteryx bilineata, territorial males defend roosting areasfor females against other males and court females throughout the year. Peripheral males in the same colonies do not defendterritories but compete with territorial males for reproductionwith females. In this study, we monitored the behavior of themales in a natural colony over three reproductive seasons.We compared morphological and age data and measured the reproductiveoutput of males adopting the territorial or peripheral tactic.No differences in body size or weight were detected betweenmale types, but the probability of adopting a tactic seemedto be age dependent. Peripherals were often young males andreplaced territorials in several cases, whereas the oppositecase was not observed. Peripherals were not excluded from reproduction,but territorials were more likely to reproduce. Variation in reproductive success was high within both male tactics, andthe reproductive success of some peripherals was comparableto territorials, but, on average, the reproductive successof territorials was more than twice as high. Therefore, behavioraltactics do not seem to be equally profitable in general butmay represent different phases in the reproductive life of manyS. bilineata males.     

Adaptations of Polygynous Breeding in the Bobolink, Dolichonyx oryzivorus

In some species of polygynous songbirds, males assist in feedingnestlings of their first (primary) female but ignore offspringof subsequent (secondary) mates. A number of adaptations importantin minimizing the disadvantages of a secondary status in femaleBobolinks (Dolichonyx oryzivorus) have been discovered. In Bobolinks, clutches of secondary females are significantlysmaller than those of primary females, thereby adjusting broodsize to correspond better with food delivery capabilities ofsecondary hens. Commencement of incubation with deposition ofthe penultimate egg allows additional brood size adjustment,for the resulting hatching asynchronism promotes efficient cullingof the late-hatching chick in times of food shortage, withoutendangering the entire brood. Secondary females differ fromprimary pairs in food exploitation techniques by capitalizingon insects found close to the nest and by showing less discriminationin food selection. Such behavior permits compensation in therate of food delivery trips to secondary nestlings so as toequal the tempo maintained by both members of the primary pair,yet results in quantitative disparities in food brought to primaryand secondary nestlings. Flexibility in male feeding responses,resulting in partial male assistance at secondary nests in situationswhere secondary brood size is exceptionally large, is also importantin helping to maximize the reproductive performance of birdsengaging in this mating strategy.     

Flying to feed or flying to mate: gender differences in the flight activity of tsetse (Glossina palpalis)

Abstract. To test the prediction that female and male tsetse should differ in their behaviour and the partitioning of their energy budgets to maximize their respective reproductive outputs, we investigated experimentally the relationship between blood intake, fat content and flight activity in virgin and mated female flies, following the same procedure as in a previous study on males.Those flies whose fat content was raised to higher levels by being fed more frequently performed more flight activity, but all females showed very little activity until day 4 after their last blood meal, thereby using only a small fraction of their fat reserves.This contrasted markedly with the large amount of flight performed by males on day 3, resulting in the depletion of their fat reserves.The difference is interpreted with respect to females flying only to find food approximately once every 3 days (and larviposition sites approximately once every 9 days), compared with males flying to find as many mates as possible during the earlier part of the feeding cycle when their energy reserves are high and feeding is a low priority.