Density‐dependent sex‐biased development of macroptery in a water strider

In wing‐polymorphic insects, wing morphs differ not only in dispersal capability but also in life history traits because of trade‐offs between flight capability and reproduction. When the fitness benefits and costs of producing wings differ between males and females, sex‐specific trade‐offs can result in sex differences in the frequency of long‐winged individuals. Furthermore, the social environment during development affects sex differences in wing development, but few empirical tests of this phenomenon have been performed to date. Here, I used the wing‐dimorphic water strider Tenagogerris euphrosyne to test how rearing density and sex ratio affect the sex‐specific development of long‐winged dispersing morphs (i.e., sex‐specific macroptery). I also used a full‐sib, split‐family breeding design to assess genetic effects on density‐dependent, sex‐specific macroptery. I reared water strider nymphs at either high or low densities and measured their wing development. I found that long‐winged morphs developed more frequently in males than in females when individuals were reared in a high‐density environment. However, the frequency of long‐winged morphs was not biased according to sex when individuals were reared in a low‐density environment. In addition, full‐sib males and females showed similar macroptery incidence rates at low nymphal density, whereas the macroptery incidence rates differed between full‐sib males and females at high nymphal density. Thus complex gene‐by‐environment‐by‐sex interactions may explain the density‐specific levels of sex bias in macroptery, although this interpretation should be treated with some caution. Overall, my study provides empirical evidence for density‐specific, sex‐biased wing development. My findings suggest that social factors as well as abiotic factors can be important in determining sex‐biased wing development in insects.     

Evaluating the life‐history trade‐off between dispersal capability and reproduction in wing dimorphic insects: a meta‐analysis

A life‐history trade‐off exists between flight capability and reproduction in many wing dimorphic insects: a long‐winged morph is flight‐capable at the expense of reproduction, while a short‐winged morph cannot fly, is less mobile, but has greater reproductive output. Using meta‐analyses, I investigated specific questions regarding this trade‐off. The trade‐off in females was expressed primarily as a later onset of egg production and lower fecundity in long‐winged females relative to short‐winged females. Although considerably less work has been done with males, the trade‐off exists for males among traits primarily related to mate acquisition. The trade‐off can potentially be mitigated in males, as long‐winged individuals possess an advantage in traits that can offset the costs of flight capability such as a shorter development time. The strength and direction of trends differed significantly among insect orders, and there was a relationship between the strength and direction of trends with the relative flight capabilities between the morphs. I discuss how the trade‐off might be both under‐ and overestimated in the literature, especially in light of work that has examined two relevant aspects of wing dimorphic species: (1) the effect of flight‐muscle histolysis on reproductive investment; and (2) the performance of actual flight by flight‐capable individuals.     

Physiological trade‐offs between flight muscle and reproductive development in the wing‐dimorphic cricket Velarifictorus ornatus

Morphology, flight muscles, and reproductive development were compared between long‐winged (LW) and short‐winged (SW) morphs of the cricket Velarifictorus ornatus (Shiraki) (Orthoptera: Gryllidae). There was no difference in body weight and pre‐oviposition between the two morphs, but LW individuals had better‐developed flight muscles than SW individuals during and after emergence of the adult. The flight muscles at adult emergence represented 11.9% of the total body weight in the LW female and 4.9% in the SW female. In addition, the weight of the flight muscle of LW females increased by 50% during the first 5 days, whereas the flight muscle of the SW variant increased only slightly after adult emergence. The process of oviposition in LW, SW, and de‐alated females varied: SW females produced more eggs at the early stage than LW females, but de‐alation could shorten the time until the peak of egg laying and caused histolysis of flight muscles of LW females. There was no significant difference in total egg production between the above three groups. In the male, unlike the female, the accessory glands of the two wing morphs enlarged continuously at the same rate. There was no difference between the two wing morphs in the mass of the testes during the first 7 days after adult emergence.     

Wing and flight muscle polymorphism in a lygaeid bug, Horvathiolus gibbicollis: determinants and life history consequences

ABSTRACT.

• 1 Horvathiolus gibbicollis (Costa), a ground-living seed-feeding bug of the mediterranean region, has two wing morphs. In macrop-terous bugs both pairs of wings are fully developed. In brachypterous ones forewings are reduced to about two-thirds and hindwings to less than a third of their length in macropters.
• 2 Each morph bred true with regard to wing length when reared under variable density, food and temperature conditions for several generations.
• 3 All F₁ offspring between crosses of the two morphs were brachypterous. In F₂ approximately 25% were macropters and 75% brachypters implying monogenic control of wingform.
• 4 Flight muscles in macropters vary from fully developed to totally reduced. This variation is determined by environmental conditions during adult life. Most young adult bugs have flight muscles, and totally starved or unmated bugs retain their flight muscles. Fed and mated females histolyse flight muscles as they start laying eggs, while most males of the same group retain their muscles.
• 5 Brachypterous bugs have a smaller thorax and larger abdomen than macropterous ones.
• 6 Brachypterous bugs reach adulthood slightly before macropterous ones, and they have a distinctly shorter adult preoviposition period.
• 7 Lifetime egg production does not differ significantly between the two wing morphs. However, the temporal pattern of egg laying is different in the two morphs. The m_x-curve of macropters starts later, then attains a higher peak and finally decreases faster than that of brachypters.
• 8 Initially, macropters lay smaller eggs than brachypters, but egg volume increases with age in macropters and eventually approaches that of brachypters.
• 9 The initial increase in reproductive effort (egg volumexegg number) of macropters is concomitant with wing muscle histolysis and the mobilization of thorax space for reproduction.
• 10 Adult survival rate does not differ between the morphs.

     

Trade‐off between flight capability and reproduction in male Velarifictorus asperses crickets

1. There are numerous data that support the trade‐off between flight capability and reproduction in female wing polymorphic insects, but the relationship between wing form and fitness remains poorly investigated in males. 2. In the present study, the development of flight muscle and gonads, spermatophore size, and multiple copulation ability were investigated in both long‐winged (LW) and short‐winged (SW) males to verify this trade‐off, using a wing dimorphic cricket species Velarifictorus aspersus (Walker). 3. The LW males had better‐developed wing muscles than the SW males on the day of emergence, and both of them developed wing muscles after emergence, but the peak of weight in SW males was achieved 4 days later than that of the LW males. The accessory glands (AG) of the LW males developed significantly slower than that of the SW males. These results suggest that development and maintenance of flight muscles have a cost on the development of reproductive organs in male V. asperses. 4. The SW males produced significantly heavier spermatophores in a single copulation and mated more often than LW males. This indicates the SW males have a higher mating success than the LW males, thereby increasing their chance of siring offspring.     

Biased dispersal of Metrioptera bicolor,a wing dimorphic bush‐cricket

In the highly fragmented landscape of central Europe, dispersal is of particular importance as it determines the long‐term survival of animal populations. Dispersal not only secures the recolonization of patches where populations went extinct, it may also rescue small populations and thus prevent local extinction events. As dispersal involves different individual fitness costs, the decision to disperse should not be random but context‐dependent and often will be biased toward a certain group of individuals (e.g., sex‐ and wing morph‐biased dispersal). Although biased dispersal has far‐reaching consequences for animal populations, immediate studies of sex‐ and wing morph‐biased dispersal in orthopterans are very rare. Here, we used a combined approach of morphological and genetic analyses to investigate biased dispersal of Metrioptera bicolor, a wing dimorphic bush‐cricket. Our results clearly show wing morph‐biased dispersal for both sexes of M. bicolor. In addition, we found sex‐biased dispersal for macropterous individuals, but not for micropters. Both, morphological and genetic data, favor macropterous males as dispersal unit of this bush‐cricket species. To get an idea of the flight ability of M. bicolor, we compared our morphological data with that of Locusta migratoria and Schistocerca gregaria, which are very good flyers. Based on our morphological data, we suggest a good flight ability for macropters of M. bicolor, although flying individuals of this species are seldom observed.     

The trade‐off to macroptery in the cricket Gryllus firmus: a path analysis in males

Among the Orthoptera, wing dimorphism, where one morph is long‐winged and flight capable while the other is short‐winged and flight incapable, is common and believed to be maintained in populations due to trade‐offs to flight capability. In males, macropterous individuals call less than micropterous individuals and as a consequence obtain fewer matings. This trade‐off is hypothesized to be mediated by the energetic costs of calling. In this paper we report results for a path analysis examining lipid weight and DLM (dorso longitudinal muscle) condition of male Gryllus firmus. We found that as DLM condition changes from a nonfunctional to a functional state, call duration decreases, and as lipid weight increases, call duration increases. The most important linked path was wing morph → DLM condition → call duration. This model is consistent with the prediction that the trade‐off between wing morph and call duration is mediated via DLM and lipid stores.     

Variation in singing behaviour among morphs of the sand field cricket,Gryllus firmus

1. Trade‐offs play a fundamental role in the evolution of many traits. 2. In wing‐polymorphic field crickets, the long‐winged morph can disperse from unfavourable environments, but has lower reproductive success than the short‐winged morph, because of costs associated with flight capability. 3. However, long‐winged individuals may minimise costs in favourable environments by histolysing their flight muscles and becoming flightless. 4. Few studies have examined how flight‐muscle histolysis affects male signalling and mate attraction. 5. We examined differences in singing activity and song characteristics among the flightless (short‐winged and histolysed long‐winged) and the flight‐capable male morphs, and female preferences for male song, in the sand field cricket. 6. We found: (i) both flightless morphs sang more than the flight‐capable morph, (ii) song characteristics varied among the three morphs, and (iii) females preferred songs characteristic of the long‐winged morphs. 7. Histolysis should increase mating success of long‐winged males because it increases singing activity. 8. Histolysed long‐winged males may have higher mating success than short‐winged males as they sing as frequently but produce more attractive songs. 9. Therefore, plasticity within the long‐winged morph may reduce costs of maturing in environments from which dispersal is not advantageous; non‐flying morphs may be pursuing different reproductive tactics.     

Differential allocation of protein resources to flight muscles and reproductive organs in the flightless wing-polymorphic bug, <Emphasis Type="Italic">Pyrrhocoris apterus</Emphasis> (L.) (Heteroptera)

Differences in the growth of dorsolongitudinal flight muscles and gonads in 1–28 days old long-winged (macropterous) and short-winged (brachypterous) adults of the firebug (Pyrrhocoris apterus L.) and the resource allocation to these organs were studied by means of total protein analysis. We found predominant allocation of food resources to flight muscles compared to reproductive organs in both macropterous males and females during the first 5 days of adult life. Subsequent histolysis of developed flight muscles coincided with increased total protein content in some reproductive organs. Initiation of intensive food intake after starvation or application of higher dose of methoprene on macropterous adults changed the resource allocation in favour of growth of reproductive organs and induced precocious histolysis of flight muscles. It indicates an involvement of juvenile hormone in wing morph-related differential allocation of resources in the bug. Increased total protein contents in the ovaries and accessory glands of starved macropterous females and males treated with methoprene, respectively, indicate that proteins derived from the methoprene-induced histolysis of the flight muscles are re-utilized for the growth of the reproductive organs. It is the first report of persistence of differential resource allocation to flight muscles and reproductive organs in the wing-polymorphic insects with non-functional macropterism.     

Adaptive significance of wing dimorphism in the absence of dispersal: a comparative study of wing morphs in the waterstrider, Gerris remigis

ABSTRACT.

• 1 Gerris remigis Say (Hemiptera; Gerridae) is primarily apterous, but populations with up to 33% macropters have been reported. The macropters seldom fly, and field studies have revealed no detectable differences between wing morphs in movement or survival at any time of year.
• 2 In this paper, life history traits of macropterous and apterous G. remigis are compared in an attempt to determine the mechanisms responsible for the maintenance of macroptery in this species in spite of the very low flight capacity and infrequent flight of macropters.
• 3 Development time, proportion breeding without diapause, and overwinter survival do not differ between morphs. However, pre-diapause macropterous females have a significantly shorter pre-oviposition period than apterous females. In contrast, post-diapause macropters begin reproducing later than apters, and have a lower cumulative fecundity.
• 4 These results suggest that macropters may be at a selective advantage in warm habitats which favour pre-diapause reproduction, but that apters should be favoured in the preferred, cool, lotic habitats.
• 5 However, crossing and rearing experiments indicate that wing morphology is primarily environmentally controlled in this species, and that the heritability of wing morphology is low, at best. In light of this, the relative impacts of purely phenotypic (environmental) variation, random effects, and the observed fitness differences on the maintenance of macroptery in this species are discussed.

     

Flight threshold, wing muscle histolysis, and alary polymorphism: correlated traits for dispersal tendency in the Gerridae

ABSTRACT. 1. This paper tests the hypothesis that selection for dispersal ability within a species influences not only the occurrence and extent of wing reduction but also the tendency or ability of the macropterous individuals to fly.
2. Flight thresholds of four species of waterstriders (Hemiptera; Gerridae) were assessed using a tethered flight technique. The species tested varied from monomorphic macropterous ( Limnoporus dissortis Drake and Harris), through seasonally polymorphic ( Gerris comatus Drake and Hottes and G. buenoi Kirkaldy), to primarily apterous ( G.remigis Say).
3. Condition of the indirect, mesothoracic flight muscles, and presence or absence of mature or developing eggs (for females) were determined by dissection of all individuals immediately following flight testing. Only individuals with normal muscles were included in the analysis of flight thresholds.
4. Comparisons among species revealed that average flight threshold and extent of flight muscle histolysis were negatively associated with the proportion of macropterous individuals. Wing reduction was also associated with significant seasonal variation in flight threshold, particularly among females.
5. These results support our initial hypothesis, and further indicate that, within the Gerridae, dispersal tendency depends not only on the proportion of macropters but also on the dispersal capability of the macropterous individuals.     

Seasonal changes in the flight apparatus of winged females and sexual males of the aphid <Emphasis Type="Italic">Tuberculatus quercicola</Emphasis> (Hemiptera: Aphididae)

Tuberculatus quercicola (Matsumura) feeds on Quercus dentata Thunberg, and has mutualistic interactions with ants. Tuberculatus quercicola has two winged morphs in its life cycle, winged females appear in summer and sexual males appear in autumn. Previous studies have shown that wing loading (ratio of body volume to wing area) is higher for the winged females, because of ant attendance, resulting in extremely low dispersal. It is known that the nutritional quality of host plants is high in spring and autumn, when leaves are growing or senescent, and low in summer when leaves are mature. This study examined the effects of seasonal plant deterioration on the development of flight apparatus (wing size and flight muscle) of winged females and males. Moreover, field intercept traps were used to examine the extent of dispersal of males. The results showed that seasonal plant deterioration affected development of the flight apparatus of winged females, particularly flight muscle. Flight muscle development was significantly higher in winged males in autumn than in winged females. However, winged males were not caught in any of the traps. The different resource allocation to the flight apparatus of winged females and males is discussed.     

Seasonal differences in body mass and circulating metabolites in a wing‐dimorphic pygmy grasshopper: implications for life history?

1. Functional wing polymorphism in insects is an intriguing topic, especially with respect to the adaptive advantage of each wing morph. The common pygmy grasshopper in Germany, Tetrix subulata, displays wing polymorphism skewed towards macropterous (LW) individuals capable of flight. Furthermore, T. subulata is known to undergo adult diapause in winter and reproduce in spring. 2. Morphometric and biochemical parameters were examined in field‐collected grasshoppers during autumn and spring to obtain a ‘snapshot’ from the same/one cohort of grasshoppers in the wild. 3. Flight muscles are largely reduced in brachypterous (SW) specimens, whereas they are well developed in LW individuals. Body mass measurements indicated gain in female T. subulata in spring, especially in LW morphs, which could be attributed to increased reproductive activity (egg production). 4. Metabolic fuel in haemolymph is differentially distributed in autumn: the concentration of lipids is highest in males, while carbohydrates are most abundant in LW specimens. The metabolic data imply that dispersal in T. subulata is predominantly in autumn, by flight in the case of LW specimens and by hopping/walking in males. 5. The season seems to be an important factor for the reproductive versus dispersal trade‐off in this species. Moreover, this study shows that morphological differences in T. subulata individuals are reflected in physiological differences that may ultimately affect behaviour and ecology.     

Adaptive significance of wing dimorphism in males ofNilaparvata lugens

The trade-offs associated with macroptery in males were investigated in a wing-dimorphic planthopper, Nilaparvata lugens (Stål) (Delphacidae, Hemiptera). Developmental time of brachypters was significantly shorter than that of macropters across a wide range of population densities, while no within-population differences between wing morphs in body weight were found. In mating experiments, brachypterous males 12 to 24 h old were almost three times more successful in competition for females than macropterous males of the same age, while in five days old males, macropters were twice as successful as brachypters. In competition for females involving direct body contact between males, brachypterous and macropterous males were equally successful. It is suggested that macroptery and delayed peak in sexual activity in males may both be influenced by the titre of juvenile hormone, as is known from females. The combination of prolonged development and delayed maximum competitive ability for mates, associated with macroptery, is likely to be disad vantageous, representing probably a penalty associated with macroptery in males in undisturbed habitats.     

Locomotor activity in adult Pyrrhocoris apterus (Heteroptera) in relation to sex, physiological status and wing dimorphism

The pattern of locomotor (walking) activity was studied in adult males and females of short‐winged (brachypterous) and long‐winged (macropterous) morph of the flightless bug Pyrrhocoris apterus (Linnaeus) (Heteroptera: Pyrrhocoridae) under constant laboratory conditions. Walking activity was measured with a computerized video system and analysed with respect to sex, physiological status (reproduction, diapause and reproductive arrest of non‐diapause type) and wing dimorphism of the bugs. The largest duration was observed in the macropterous females with reproductive arrest of non‐diapause type (average 6 h per day) and the shortest duration in diapausing brachypterous females and males (average less than 2 h per day). This was reflected also in the overall time spent by walking during the first 14 days after imaginal ecdysis. The time spent by walking significantly increased in the macropterous morph as the bugs aged, whereas in diapausing brachypters the time spent by walking decreased with age. No linear relationship between walking activity and age was found in reproductive brachypterous morph. The bugs of all experimental groups moved mostly during the photophase and were almost inactive during the scotophase. Thus, walking activity in P. apterus is diurnal, irrespective of the wing morph, physiological status, sex and age. Contrary to the macropterous morph, where the locomotor activity of females during photophase was significantly higher than in males, no significant differences were found between the locomotor activities of brachypterous males and females. The observed differences in locomotor activity are discussed in relation to different roles of two wing morphs in the life history of this heteropteran.     

Spatial sorting may explain evolutionary dynamics of wing polymorphism in pygmy grasshoppers

Wing polymorphism in insects provides a good model system for investigating evolutionary dynamics and population divergence in dispersal‐enhancing traits. This study investigates the contribution of divergent selection, trade‐offs, behaviour and spatial sorting to the evolutionary dynamics of wing polymorphism in the pygmy grasshopper Tetrix subulata (Tetrigidae: Orthoptera). We use data for > 2800 wild‐caught individuals from 13 populations and demonstrate that the incidence of the long‐winged (macropterous) morph is higher and changes faster between years in disturbed habitats characterized by succession than in stable habitats. Common garden and mother‐offspring resemblance studies indicate that variation among populations and families is genetically determined and not influenced to any important degree by developmental plasticity in response to maternal condition, rearing density or individual growth rate. Performance trials show that only the macropterous morph is capable of flight and that propensity to fly differs according to environment. Mark–recapture data reveal no difference in the distance moved between free‐ranging long‐ and short‐winged individuals. There is no consistent difference across populations and years in number of hatchlings produced by long‐ and shorter‐winged females. Our findings suggest that the variable frequency of the long‐winged morph among and within pygmy grasshopper populations may reflect evolutionary modifications driven by spatial sorting due to phenotype‐ and habitat type–dependent emigration and immigration.     

Sexual conflicts, loss of flight, and fitness gains in locomotion of polymorphic water striders

In insect wing polymorphism, morphs with fully developed, intermediate, and without wings are recognized. The morphs are interpreted as a trade‐off between flight and flightlessness; the benefits of flight are counterbalanced by the costs of development and the maintenance of wings and flight muscles. Such a trade‐off has been widely shown for reproductive and developmental parameters, and wing reduction is associated with species of stable habitats. However, in this context, the role of water locomotion performance has not been well explored. We chose seven water striders (Heteroptera: Gerridae) as a model to study this trade‐off and its relation to sexual conflicts, namely, Aquarius elongatus (Uhler), Aquarius paludum (Fabr.), Gerris insularis (Motschulsky), Gerris nepalensis Distant, Gerris latiabdominis Miyamoto, Metrocoris histrio (White), and Rhagadotarsus kraepelini Breddin. We estimated the locomotion performance as the legs’ stroke force, measured on tethered specimens placed on water with a force transducer attached to their backs. By dividing force by body weight, we made performance comparisons. We found a positive relationship between weight and force, and a negative one between weight and the force‐to‐weight ratio among species. The trade‐off between water and flight locomotion was manifested as differences in performance in terms of the force/weight ratio. However, the bias toward winged or wing‐reduced morphs was species dependent, and presumably related to habitat preference. Water strider species favouring a permanent habitat (G. nepalensis) showed higher performance in the apterous morph, but in those favouring temporary habitats (A. paludum and R. kraepelini) morphs’ performance did not differ significantly. Males had higher performance than females in all but three species studied (namely, A. elongatus, G. nepalensis, and R. kraepelini); these three have a type II mating strategy with minimized mating struggle. We hypothesized that in type I mating system, in which males must struggle strongly to subdue the female, males should outperform females to copulate successfully. This was not necessarily true among males of species with type II mating.     

Temporal pattern of feeding activity in the firebug Pyrrhocoris apterus and its relation to sex, wing dimorphism and physiological state of adults

Abstract.  The present study tested whether the pattern of feeding activity in the firebug Pyrrhocoris apterus (L.) is sex- and wing morph-related, diurnal or nocturnal, as well as whether the feeding rhythm persists in constant darkness. Temporal patterns of feeding activity are analysed in macropterous and brachypterous adults reared under long-day (LD 18 : 6 h) and short-day (LD 12 : 12 h) photoperiods, and in adults transferred to constant darkness. In females, the total feeding activity is highest in long-day reproductively active brachypters, intermediate in short-day diapausing brachypters, and lowest in macropters; the differences among males are substantially smaller. Although the total feeding activity of macropterous males is higher than in macropterous females, no sex-related differences are found in feeding activity of diapausing and reproductively active brachypters. The frequency of feeding exhibits sex-related differences, with obviously higher values in males. Mean feeding periods of macropterous and reproductively active brachypterous males are shorter than in females of the same wing morph. Mean interfeeding periods are longest in macropters, intermediate in diapausing brachypters, and shortest in reproductively active brachypters, and always lower in males than in females. The study shows that the feeding activity of P. apterus adults is age-, sex- and wing morph-related, and exhibits a diurnal pattern, except in reproductively active brachypterous females. The latter do not express a clear diurnal rhythm of feeding, presumably because of interactions with cycles of egg development and oviposition. The persistence of diurnal rhythm of feeding activity in short-day brachypterous females transferred to constant darkness indicates an endogeneity of this rhythm in P. apterus .     

Reproductive cost of flight capability: a comparison of life history traits in wing dimorphic planthoppers

Abstract. 1. Reproductive costs associated with flight capability were evaluated in the wing dimorphic planthopper, Prokelisia dolus Wilson, by comparing the life history of traits of winged (macropterous) and flightless (brachypterous) females under controlled laboratory conditions.
2. Macropters with large thoraces and fully developed wings maintain a greater investment in flight apparatus than brachypters with small thoraces and reduced wings.
3. Associated with greater flight capability in the macropter of P.dolus are shorter adult life, decreased total fecundity, and delayed age at first reproduction compared to brachypterous females.
4. Under field conditions where mortality is high, the difference in realized fecundity between the two wing forms living on similar resources is further exaggerated with the brachypter having the greater advantage.
5. When the life history traits of the wing forms of P. dolus are compared with traits for nine other species of planthoppers, two similarities emerge. First, the preoviposition period of the macropterous wing form is always longer than that for the brachypter resulting in a reproductive delay. Second, most studies show that macropters are less fecund than brachypters.
6. There is no general tendency among planthopper species for macropterous adults to live fewer days or develop more slowly as nymphs compared to their flightless counterparts.
7. The reproductive delay and reduced fecundity of the volent wing form of planthoppers supports the notion that flight capability is costly and that phenotypic trade-offs between flight and reproduction exist.     

Genetic correlation of wing polymorphism between females and males in the oriental chinch bug,Cavelerius saccharivorus Okajima (Heteroptera: Lygaeidae)

Genetic correlations of the wing form and the relative wing length between females and males were estimated in the oriental chinch bug, Cavelerius saccharivorus, by calculating the correlation between the sexes of the proportion macropterous or the mean relative wing length in full-sib families obtained from different wing forms of parents emerged in a high density population. There was a significantly positive genetic correlation between the sexes in both the proportion macropterous and the mean relative wing length. However, the appearance rate of macropters tended to be much lower in males than in females under the rearing conditions which promote the appearance of macropters. This was evident especially in the offspring of brachypterous parents. These indicated that in C. saccharivorus the wing polymorphism of males is not a simple result of the genetic correlation of wing morphology between the two sexes. It was considered that both of the female and male fitness advantages to wing reduction, as well as the genetic correlation between the sexes, would influence the evolution of wing polymorphism in this species.