Wing morph-related physiological differences in adults of temperate population of Pyrrhocoris apterus (L.) (Heteroptera: Pyrrhocoridae)

The reproductive and diapausing adult females of brachypterous morph and macropterous females with reproductive arrest of non-diapause type, originating from the laboratory cultures of Pyrrhocoris apterus, were studied for their feeding and drinking behaviour, digestive enzyme activities, and carbohydrate and lipid contents. The highest feeding and drinking activities were observed in reproductive brachypters, the lowest in macropters. Macropters also differed from brachypters by lower activities of gut lipase, peptidase and protease, lower concentration of haemolymph sugars, and lower weight of fat body, which probably reflects their low feeding activity. The total content of fat body lipids was also lower in macropters (0.6 mg) than in reproductive and diapausing brachypters (4.6 and 7.5 mg, respectively) on day 14. A very high amount of glycogen was found in the fat body of diapausing brachypters, 363 micrograms on day 14, as opposed to 15 and 80 micrograms in macropterous and reproductive brachypterous females, respectively. The obtained data indicate that the most important difference between macropterous and brachypterous females with different types of reproductive arrest consists of an enhanced mobilization of lipids for dispersal in macropters and accumulation of energetic reserves for hibernation in brachypters.     

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 .     

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.

     

Wing morph-related physiological differences in adults of temperate population of Pyrrhocoris apterus (L.) (Heteroptera: Pyrrhocoridae)

The reproductive and diapausing adult females of brachypterous morph and macropterous females with reproductive arrest of non-diapause type, originating from the laboratory cultures of Pyrrhocoris apterus, were studied for their feeding and drinking behaviour, digestive enzyme activities, and carbohydrate and lipid contents. The highest feeding and drinking activities were observed in reproductive brachypters, the lowest in macropters. Macropters also differed from brachypters by lower activities of gut lipase, peptidase and protease, lower concentration of haemolymph sugars, and lower weight of fat body, which probably reflects their low feeding activity. The total content of fat body lipids was also lower in macropters (0.6 mg) than in reproductive and diapausing brachypters (4.6 and 7.5 mg, respectively) on day 14. A very high amount of glycogen was found in the fat body of diapausing brachypters, 363 μg on day 14, as opposed to 15 and 80 μg in macropterous and reproductive brachypterous females, respectively. The obtained data indicate that the most important difference between macropterous and brachypterous females with different types of reproductive arrest consists of an enhanced mobilization of lipids for dispersal in macropters and accumulation of energetic reserves for hibernation in brachypters.     

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.     

Wing morph-specific differences in the metabolism and endocrine control of reserve mobilization in adult males of a flightless bug, <Emphasis Type="Italic">Pyrrhocoris apterus</Emphasis> (L.) (Heteroptera)

The differences in the metabolism and endocrine control of reserve mobilization in long-winged (macropterous) and short-winged (brachypterous) males of a flightless firebug (Pyrrhocoris apterus) were studied. We found that protein content in the gut was significantly lower in 5–10 day-old macropterous males due to their fasting and higher in 28 day-old ones than in the same aged brachypterous counterparts as the result of renewed food intake. Overall protease activity was significantly lower in 10–14 day-old macropters, while an abrupt increase in the activity starting on day 21 after adult ecdysis was also associated with renewal of the food intake. The levels of carbohydrates in haemolymph were only slightly lower in 1–10 day-old macropterous males than in the same aged brachypters. However, more than twofold higher lipid content in haemolymph of 7–10 day-old macropterous males than in the same aged brachypterous males was found. Higher mobilization of lipid reserves from the fat bodies in macropterous males was accompanied by more intensive adipokinetic response and higher levels of adipokinetic hormone in the body. It is the first report of endocrine regulation of wing morph-related differences in the lipid mobilization in males of wing-polymorphic insects.     

Does alary dimorphism imply dispersal dimorphism in the waterstrider,Gerris remigis?

ABSTRACT.

• 1 The hypothesis that wing dimorphism reflects dimorphism for dispersal ability is tested in two populations of stream-dwelling waterstriders, Gerris remigis Say, in southern Quebec, Canada.
• 2 Movements were assessed directly by recaptures of marked adults, and indirectly by comparisons of residence times and patterns of disappearance of macropterous and apterous morphs. Sampling was done weekly, over a period of 26 months, and 4828 adult G.remigis were individually marked during this time.
• 3 Movements of >100 m were very rare for both morphs. The movement patterns of the two morphs were very similar, and differed only over the winter, when no macropters moved upstream. This latter observation suggests that macropters may be less successful than apterous individuals at moving overland, or rowing against a current at this time of year.
• 4 Residence times and patterns of disappearance of the two morphs were very similar during all seasons.
• 5 These results suggest that macropterous G.remigis do not, in general, disperse using any means unavailable to the apterous morph, and that macropters in this species should not be simply categorized as long-distance dispersers.

     

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.     

Enhancement of short wing formation and ovarian growth in the genetically defined macropterous strain of the brown planthopper,Nilaparvata lugens

When JH II, III or methoprene was applied in the nymphal stages to two different strains of the brown planthopper which were selected to produce long (macropterous) or short (brachypterous) wing forms, no effect was observed on the molting profile or metamorphosis. Brachypterization of a majority of the presumptive macropters was, however, observed by application of these chemicals, although there was no effect on wing form in the presumptive brachypters. The results show that the sensitive periods for the brachypterization of the presumptive macropters falls between early antepenultimate instar and within 1 or 2days of the penultimate instar, and that the chemicals were effective, in the following order of potency: methoprene>JH III>JH II. Ovarian growth was greatly enhanced in the presumptive macropters when JH III or methoprene was applied twice, within 12h of the 3rd or 4th nymphal instar and 6h before adult emergence. JH II on the other hand had no effect on ovarian growth when applied to the presumptive macropters at any of the nymphal stages. None of the chemicals had any effect on ovarian growth in the presumptive brachypters.     

Trade‐offs to flight capability in Gryllus firmus: the influence of whole‐organism respiration rate on fitness

Wing dimorphism, where some macropterous long‐winged (LW) individuals can fly whereas micropterous short‐winged (SW) individuals cannot, is common in insects and believed to be maintained in part by trade‐offs between flight capability and reproductive traits. In this paper we examine differences in whole‐organism respiration rate between wing morphs of the sand cricket Gryllus firmus. We hypothesized that maintenance of the flight apparatus would result in elevated CO₂ respired because of the high metabolic cost of these tissues, which, in turn, constrain resources available for egg production in females. As the trade‐off involves calling behaviour in males, we predicted no equivalent constraint on organ development in this sex. We found female macropters (particularly older crickets) had significantly higher residual respiration rates than micropters. In males, we found only marginal differences between wing morphs. In both sexes there was a highly significant effect of flight muscles status on residual respiration rate, individuals with functional muscles having higher respiration rates. Both female and male macropters had significantly smaller gonads than micropters. Whole‐organism residual respiration rate was negatively correlated with fecundity: macropterous females with high respiration rates had smaller gonads compared with macropterous females with lower respiration rates.     

Ecological significance of the wing polymorphism of the oriental chinch bug,Cavelerius saccharivorus Okajima (Heteroptera: Lygaeidae)

The wing polymorphism of the oriental chinch bug, Cavelerius saccharivorus, was studied in relation to its reproductive strategy. The frequency distribution of wing form in terms of the relative wing length (R.W.L.) changed with increase in the population density from a single modality biased toward the brachypterous form to bimodality with both macropterous and more extreme brachypterous forms. Since some evidences in the field showed that fliers are limited to macropters, such a bimodality of wing form indicated that C. saccharivorus employs a mixed strategy with some portion of adults staying on in the same habitat, whereas the rest disperse. Moreover, macropters were larger in body size than brachypters emerging in high density populations, although smaller than brachypters emerging in low density populations. Larger body size as well as the delay of ovarian maturation in macropters was considered to be a beneficial trait for migratory behaviour.     

Movement,colonization, and establishment success of a planthopper of prairie potholes,Delphacodes scolochloa (Hemiptera: Delphacidae)

Abstract 1. Movement, and particularly the colonisation of new habitat patches, remains one of the least known aspects of the life history and ecology of the vast majority of species. Here, a series of experiments was conducted to rectify this problem with Delphacodes scolochloa Cronin & Wilson, a wing‐dimorphic planthopper of the North American Great Plains. 2. The movement of brachypterous and macropterous planthoppers within and among host‐plant patches was quantified. Also, an experiment was conducted to assess whether planthopper propagule size (i.e. number of colonists) influenced the presence of planthopper adults or eggs over time, planthopper population growth rate (R₀), and abundance or impact of an egg parasitoid. 3. Delphacodes scolochloa movement was well described by a simple diffusion model. As expected, brachypters were less dispersive than macropters – mean displacement distances among patches were three times greater for macropters (2.8 m vs. 8.1 m per day). 4. Number of colonists of vacant patches increased with increasing patch size (both wing forms) and decreased with increasing isolation (brachypters only). At the scale of individual potholes (<38 m), brachypters were dispersal limited. 5. Establishment success was strongly influenced by propagule size. An Allee effect constrained the establishment of new populations, but low establishment success was not a result of mate limitations or the presence of natural enemies (i.e. egg parasitoids).6. These movement data reveal important insights regarding the spatial population structure and spread of D. scolochloa.     

Reproduction and egg diapause of the oriental chinch bug,Cavelerius saccharivorus okajima (Heteroptera: Lygaeidae), in the subtropical winter season in relation to its wing polymorphism

Reproduction and egg diapause of the oriental chinch bug, Cavelerius saccharivorus, in the subtropical winter season were investigated in relation to its wing polymorphism. Macropterous females collected from the southern part of Okinawa Is. in the autumn season delayed their oviposition and were less fecund early in the adult life period, but survived much longer than brachypterous females collected from the same locality. The total fecundity was not significantly different between wing morphs. The diapause of eggs laid by brachypters tended to be terminated more easily at a high temperature than that of eggs laid by macropters. This indicated that the eggs laid by macropters were more intense in their diapause than those laid by brachypters. However, irrespective of the parental wing form, diapause showed considerable variation in its intensity within and between clutches.     

Rapid range expansion of a wing-dimorphic bush-cricket after the 2003 climatic anomaly

During recent decades, many species have responded to global warming by poleward range expansions. We require a better mechanistic understanding of the nature and extent of such processes to assess how climate change might affect biodiversity. Wing-dimorphic bush-crickets are excellent objects to study dispersal and colonization processes at the range margin because the long-winged morphs (macropters) represent dispersal units of otherwise flightless species. Moreover, these insects produce noisy songs and can easily be mapped. The present study comprised a detailed investigation of the population dynamics and genetics at the edge of the range of Roesel's bush-cricket, Metrioptera roeselii . We mapped the distribution of this insect in a previously unoccupied area of 185 km² and examined the genetic structure at the range margin using four polymorphic microsatellite loci. The results obtained demonstrate that the European heat wave in 2003 induced a strong immigration of macropters in the area stemming from multiple sources, whereas only few immigrants were recorded in the two subsequent years. Macropters were genotyped in a distance of up to 19.1 km from their origin, considerably exceeding the known dispersal distances for this species. Moreover, the data show that strong local founder effects are equalized on a large scale by the high number of immigrants from multiple sources. The present study demonstrates that macropters are of high significance for the range expansion of wing-dimorphic insects because a single-year climatic anomaly can induce strong dispersal processes.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 97 , 118–127.     

Reproductive properties of the oriental chinch bug,Cavelerius saccharivorus Okajima (Heteroptera: Lygaeidae), in relation to its wing polymorphism

Reproductive properties of the oriental chinch bug, Cavelerius saccharivorus, were investigated for three types of female adults: brachypters produced in both high and low density populations and macropters produced in high density populations. With respect to egg-laying potential in terms of clutch size, clutch number, and total fecundity, macropters were superior to brachypters produced in the same high density population, although inferior to brachypters produced in the low density population. The mean fecundity of female adults in each type was positively correlated with mean body length. Macropterous females markedly prolonged their initiation of both copulation and oviposition and had a much longer life span compared with both types of brachypters. However, there was no fundamental difference in reproductive schedules between the two types of brachypters.     

Relation between temporal persistence of host plants and wing length in leafhoppers (Hemiptera: Auchenorrhyncha)

Abstract.

• 1 Wing form frequencies in 255 populations of 101 species of leafhoppers (Auchenorrhyncha) in temporary and permanent habitats were documented.
• 2 The proportion of brachypterous specimens in the leafhopper assemblages on ruderal host plants in temporary habitats (median 2%, range 0–8%) was significantly lower than that on permanent host plants in undisturbed habitats (median 22%, range 0–94%).
• 3 Leafhopper species typical of temporary habitats were either monomorphic, macropterous, or wing-dimorphic with macropterous forms prevailing in both sexes.
• 4 Among the eighty-nine species recorded in permanent habitats, forty-five species were wing dimorphic. In forty-one dimorphic species, a brachypterous form prevailed. This prevalence was found for both sexes in thirty-one species, for only females in nine species and for only males in one species.
• 5 The prevalence of brachypters in males, but not in females, found in Anoscopus flavostriatus, is probably the first such documented case in Auchenorrhyncha.
• 6 The hypothesis is proposed that in temporary habitats, density-dependent production of macropters in wing dimorphic species is an adaptation to frequent habitat deterioration caused by factors independent of the density of the species.
• 7 The predominance of brachypters in permanent habitats indicates that a density-dependent decrease in fitness usually does not offset the potential decrease in fitness connected with macroptery and dispersal. Because of this inability of leafhopper populations to decrease significantly the quality of their resources, a high population density cannot be used as a predictor of future quality of these resources, which is information essential for efficient dispersal behaviour.

     

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.

     

Ecological significance of wing polymorphism in Fulgoroidea which inhabit tidal salt marshes

• 1 The vegetation of New Jersey tidal salt marshes is composed primarily of two grasses, Spartina patens, which occupies a narrow elevational zone of high marsh and varies little in structure from site to site, and Spartina alterniflora, an intertidal species which occurs as two spacially separated growth forms (tall and short). Fulgoroids, polymorphic for wing length, inhabit these grasses.
• 2 Populations of the common fulgoroid inhabiting short form S.alterniflora were composed of equal numbers of macropters and brachypters. Mesothoracic wings of brachypters were subequal in length to the abdomen allowing for short but inefficient flights compared to macropters.
• 3 Fulgoroids residing in S.patens produced mostly brachypters having small meso-and vestigial metathoracic wings and were incapable of flight.
• 4 Brachypter density of all fulgoroids was correlated with the seasonal increase in biomass of the host grass, while macropter density was not.
• 5 Peak macropter density occurred shortly before maximum biomass of the host grass was attained.
• 6 The production of macropterous forms was correlated with high levels of crowding incurred during nymphal stages.
• 7 Spatial and temporal variation in the structure of the host grasses and habitat reliability are suggested as important factors dictating the wing-polymorphism strategies of fulgoroids.