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.     

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.     

稻飞虱翅型纯系后代个体的翅型分化对光周期变化不敏感

【目的】为了明确光周期和遗传因子在稻飞虱翅型分化中的作用, 研究了3种稻飞虱（褐飞虱Nilaparvata lugens、白背飞虱Sogatella furcifera和灰飞虱Laodelphax striatellus）翅型纯系或近纯系在不同光照时数下的翅型分化比率。【方法】以经过5~45代连续翅型筛选后的褐飞虱、白背飞虱和灰飞虱的长翅型和短翅型纯系或近纯系为材料, 在室内分别测定了其在长光照（16和20 h）、短光照(4~12 h)和正常光照(14 h) 3类光周期条件下饲养后, 雌、雄成虫中长翅和短翅个体出现的比率及存活率。【结果】白背飞虱和灰飞虱的长翅型纯系M♂×M♀或短翅型纯系B♂×B♀在不同光周期下的翅型比率均无显著差异（P>0.05）。褐飞虱短翅型近纯系B♂×B♀的雌虫短翅率和成虫总短翅率在不同光周期下也无显著差异（P>0.05）, 但雄虫短翅率在正常光照14 h和短光照4 h下显著高于长光照20 h下的（P<0.05）。当褐飞虱短翅型达到纯系后, 其后代翅型在6~16 h光照条件下无显著差异。褐飞虱长翅型近纯系M♂×M♀的后代虽有短翅个体出现, 但是雌虫和雄虫的各自短翅率在不同光周期下无显著差异（P>0.05), 仅总体短翅率在12 h光照条件下的显著高于16 h下的（P<0.05）。褐飞虱长、短翅型杂交筛选品系M♂×B♀的雌虫短翅率随光照时数的延长而升高; 灰飞虱杂交筛选品系M♂×B♀的短翅雄虫随光照时数的缩短而增多（P<0.05）, 但当筛选代次达到45代时, 这种趋势不再显著。3种稻飞虱长翅型和短翅型纯系或近纯系若虫的存活率会稍低于长、短翅型杂交后代的存活率, 但长、短翅型品系的存活率在6~16 h光照条件下差异不显著(P>0.05)。【结论】稻飞虱翅型分化对光周期的反应受飞虱本身遗传背景的影响, 翅型纯系后代个体的翅型分化对光周期变化不敏感。     

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.     

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.     

A sexual conflict in collared flycatchers,Ficedula albicollis: early male moult reduces female fitness

A sexual conflict over levels of parental care occurs in most animals with biparental care, and studies of sexual differences in levels of parental care have usually focused on its intra-annual fitness consequences. We investigated inter-annual fitness consequences of a sexual difference in timing of feather replacement (moult) in collared flycatchers (Ficedula albicollis). In this study, males overlapped reproduction and moult more often than females, they also initiated their moult at an earlier stage of breeding than females. Females mated to males with a moult-breeding overlap had significantly lowered survival chances than females mated with males initiating moult after breeding. Furthermore, females mated with moulting males risked a lowered future fecundity in terms of a delayed start to breeding in the following season. However, early moulting males achieved a similar reproductive success as males initiating moult after breeding. Likewise, male survival probability to the following breeding season did not differ between early and late moulting individuals, nor was there any evidence that males gained or lost in future mating advantages by moulting early. These results show not only that a sexual conflict over timing of moult may operate, but also that it can impose severe fitness consequences, in terms of reduced future fecundity and survival probability, upon the ''losing'' sex.     

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 .     

THE EVOLUTION OF WING DIMORPHISM IN INSECTS

Wing-dimorphic insects are excellent subjects for a study of the evolution of dispersal since the nondispersing brachypterous morph is easily recognized. The purpose of this paper is to develop a framework within which the evolution of wing dimorphism can be understood. A review of the literature indicates that the presence or absence of wings may be controlled by a single locus, two-allele genetic system or a polygenic system. Both types of inheritance can be subsumed within a general threshold model. An increase in the frequency of a brachypterous morph in a population may result from an increased relative fitness of this morph or the emigration of the macropterous type. The abundance of wing-polymorphic species argues for an increased fitness of the brachypterous form. An analysis of the life-history characteristics of 22 species of insects indicates that the brachypterous morph is both more fecund and reproduces earlier that the macropterous morph. Unfortunately, data on males are generally lacking. It is suggested that suppression of wing production results when some hormone, perhaps juvenile hormone, exceeds a threshold value during a critical stage of development. Further, it is known that in the monomorphically winged species Oncopeltus fasciatus both flight and oviposition are regulated by the titer of juvenile hormone. These observations are used to construct a possible pathway for the evolution of wing dimorphism. This suggests that evolution to a dimorphic species requires both an increase in the rate of production of the wing suppressing hormone and a change in the threshold level at which wing and wing-muscle production are suppressed. The stage in this evolutionary sequence that an organism will reach depends on the stability of the habitat.     

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.     

Males of the two-spotted spider mite attempt to copulate with mated females: effects of double mating on fitness of either sex

In Tetranychus urticae (Acari: Tetranychidae), when the intervals between first and second copulation are more than 24 h, only the first copulation is effective for females. Therefore, adult males should copulate only with virgin females, but not with females that copulated more than 1 day ago. Indeed, T. urticae males preferred virgin females to mated females under dual choice conditions. In the absence of virgin females, however, 60% of males copulated with mated females (n = 30). Therefore, the effects of male copulation behaviour on male and mated-female fitness were examined, respectively. Since T. urticae is arrhenotokous (i.e., only daughters have genes derived from their father), the proportion of females among the offspring was used as an index of male fitness. After males had lived with/without a mated female, the males were allowed to copulate with a virgin female. The proportion of females among the offspring did not differ between males with and without a female. On the other hand, when mated females lived with an adult male, their egg production was lower than mated females without a male. These results suggest that males do not seem to obtain fitness benefit from the copulation behaviour and that mated females incur a fitness cost due to the male behaviour.     

Population studies ofCavelerius saccharivorus Okajima (Heteroptera: Lygaeidae): Adult dispersal in relation to the density

Two adjacent stations (H and L) were set up to study movement of C. saccharivorus adults in sugarcane fields. At the beginning of the study the density of C. saccharivorus including all stages of development was quite different between the two. The density of the first generation adult on Station H was about 5 times that on Station L. The number of C. saccharivorus on both the stations became almost the same one month after the beginning of the study. At the beginning of the study macropterous adults were more numerous in Station H than in Station L. However percentage of macropterous adults on Station L increased after one month whereas that on Station H declined. About 2,000 marked adults were released on each station during the early period of the emergence of the first generation adult. Marked insects were recaptured on both the stations one month after the release. The adults released on the dense population (H) tended to disperse more actively than those on the scarce population (L). Marked macropterous adults moved more actively than brachypterous ones. The density related dispersal of adults was considered to be an important factor to regulate the population density.     

Population studies ofCavelerius saccharivorus Okajima (Heteroptera: Lygaeidae): Adult dispersal in relation to the density

Summary Two adjacent stations (H and L) were set up to study movement ofC. saccharivorus adults in sugarcane fields. At the beginning of the study the density ofC. saccharivorus including all stages of development was quite different between the two. The density of the first generation adult on Station H was about 5 times that on Station L. The number ofC. saccharivorus on both the stations became almost the same one month after the beginning of the study. At the beginning of the study macropterous adults were more numerous in Station H than in Station L. However percentage of macropterous adults on Station L increased after one month whereas that on Station H declined. About 2,000 marked adults were released on each station during the early period of the emergence of the first generation adult. Marked insects were recaptured on both the stations one month after the release. The adults released on the dense population (H) tended to disperse more actively than those on the scarce population (L). Marked macropterous adults moved more actively than brachypterous ones. The density related dispersal of adults was considered to be an important factor to regulate the population density.     

Sublethal effects of abamectin on the development,fecundity, and wing morphs of the brown planthopper Nilaparvata lugens

The brown planthopper Nilaparvata lugens negatively affects rice yield by sucking nutrients from the rice stem and spreading viruses. In this study, the effects of sublethal concentrations of abamectin on development, fecundity, and wing morphs of N. lugens were investigated. Treatment with sublethal concentrations of abamectin showed no significant effects on the developmental period of F₀ nymphs. Although LC₁₀ and LC₂₅ treatments resulted in 10% and 25% mortality, the LC₂₅ treatment significantly prolonged the lifespan of macropterous and brachypterous females. Abamectin-treated brachypterous females showed significantly lower fecundity than control females. Furthermore, abamectin treatment showed no significant effects on the developmental period of F₁ nymphs. However, LC₂₅ treatment significantly inhibited the fecundity of brachypterous F₁ females and significantly reduced the proportion of macropterous F₁ females and brachypterous F₁ males. LC₂₅ treatment showed no significant effects on the fecundity of macropterous F₁ females. Considering the proportion of macropterous and brachypterous F₁ females, the relative fitness of the macropterous F₁ nymphs in the control, LC₁₀, and LC₂₅ treatment groups was 1, 1.02, and 0.84, respectively, and that of brachypterous F₁ nymphs was 1, 0.79, and 0.93, respectively. Sublethal concentrations of abamectin inhibited N. lugens emergence. The present findings indicate the potential of abamectin for N. lugens field control.     

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.     

Differences in adipokinetic response of Pyrrhocoris apterus (Heteroptera) in relation to wing dimorphism and diapause

Three experimental groups of adult females (reproductive and diapausing brachypters, and macropters with reproductive arrest) of Pyrrhocoris apterus (Linnaeus) (Heteroptera: Pyrrhocoridae) from a temperate population were analysed for their adipokinetic responses. The adipokinetic response, expressed as an increase of haemolymph lipids after injection of adipokinetic hormone from Locusta migratoria (Lom-AKH-I), was assessed in relation to age, wing dimorphism and type of reproductive arrest. Two pmols of Lom-AKH-I were used for determination of adipokinetic responses. The increase of haemolymph lipids in all experimental groups of females induced by this dose of the hormone was comparable with that induced by crude extract of the bug’s own corpora cardiaca. The level of adipokinetic response after injection of 2 pmol of Lom-AKH-I was significantly higher in macropterous and diapausing brachypterous females than in reproductive brachypterous females. However, significantly higher contents of haemolymph lipids in control macropterous females than those found in the control reproductive and diapausing brachypterous females of the corresponding age revealed wing-morph-related differences in lipid metabolism. The observed wing morph- and diapause-related differences in the content of haemolymph lipids and adipokinetic response, respectively, are discussed in relation to the different roles of two wing morphs in the life history of this heteropteran.     

Dispersal and reproductive properties of sugarcane bugs,Cavelerius saccharivorus

The distribution of sugarcane bugs, Cavelerius saccharivorus is remarkably patchy at time of the peak emergence of the first generation adult in early summer. In population near carrying capacity 70% of adults become macropterous, and they move to sparse populations or vacuum areas. The experiment on the reproductive difference between females from field populations with different densities, showed that the overcrowding restricted their oviposition. On the further experiment it was shown that reproductive ability of macropterous adults or dispersers was not much inferior to that of brachypterous from sparse populations. Overcrowding at time of the peak emergence is reduced by the dispersal. Hence the intraspecific competition is a transient condition. The oviposition is at first restricted in residents of dense populations as compared with brachypterous adults of sparse populations, but the difference becomes small as the former density decreases by the emigration. The last section considers the relation of the reproductive rate and dispersal risk to the rate of dispersal with the simple model, which explains the characteristic dispersal of this species.     

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.

     

三种稻飞虱翅型分化的遗传分析

为了明确褐飞虱Nilaparvata lugens、 白背飞虱Sogatella furcifera和灰飞虱Laodelphax striatellus 3种稻飞虱翅型分化的遗传规律与差异, 采用翅型筛选与杂交遗传的实验方法, 研究了3种飞虱在秧苗期水稻上的翅型选择响应与杂交遗传规律。结果表明： 3种稻飞虱的翅型具有较强的选择响应, 并且长翅型纯系在白背飞虱中最易筛选得到, 灰飞虱的次之, 而褐飞虱的最难。3种稻飞虱的长翅(M)雄虫与短翅(B)雌虫配对(M♂×B♀)筛选3~5代后, 95%~100%的雄虫和雌虫分别稳定为长翅型和短翅型。筛选和杂交实验结果表明, 褐飞虱的翅型决定基本符合常染色体上的一对等位基因调控的从性性状遗传规律, 雄虫中长翅为显性, 而雌虫中短翅为显性。翅型的表型还受除基因型外的其他条件的影响, 利用长翅雄虫与长翅雌虫后代中出现的极少数的短翅雄虫与短翅雌虫进行配对, 其后代中各翅型出现的比率与长翅雌虫和长翅雄虫配对的无显著差异; 同样, 在短翅雄虫与短翅雌虫配对的后代中也有相同的结果。白背飞虱和灰飞虱在该筛选条件下很少有短翅雄虫出现, 两者翅型的遗传调控较为相似, 可用由两对等位基因控制的性状来解释筛选和杂交实验的结果, 其中一对等位基因位于性染色体上, 调控雄性的翅型, 且长翅为显性; 另一对位于常染色体上, 调控雌性的翅型, 且短翅为显性。据此认为, 3种飞虱翅型决定基因的显隐性在不同性别间的差异, 以及翅表型与基因型的不一致性, 是稻飞虱种群在不同条件下均可灵活调控翅型的重要遗传机制。     

Reproductive strategies of the larval parasitoid Microplitis croceipes

Mate choice may have important consequences for offspring sex ratio and fitness of haplodiploid insects. Mate preference of females of the solitary larval parasitoid Microplitis croceipes (Cresson) (Hymenoptera: Braconidae) for virgin and mated males, and vice versa, and the reproductive consequences (i.e., the sex ratio expressed as the proportion of male offspring) were examined in choice and non‐choice experiments. In addition, the effect of repeated rapid and daily copulation of an individual male on the sex ratio of offspring of the female mates was assessed. Males preferred virgins over mated females, whereas females copulated with a male irrespective of his mating status. In both the rapid and daily copulation assay, females copulating with a male that had copulated five times or more produced a higher sex ratio than females that had copulated with a virgin male. Females that copulated with virgin males once or twice produced a significantly and considerably lower sex ratio than females that first copulated with a sperm‐depleted male followed by a virgin male. This indicates that copulating with a sperm‐depleted male has costs and limits acquisition by the female of sperm from virgin males.     

Wing structure and polymorphism in minute scavenger beetles (Coleoptera,Latridiidae)

The main structural elements of the hind wing in 56 species of the family Latridiidae (Coleoptera) are analyzed. In macropterous forms, wing venation is reduced to 3 modified veins. 10 areas of sclerotization of the wing membrane are distinguished. Three forms with different degrees of wing reduction are revealed: the brachypterous, the micropterous, and the apterous form. Among 56 species examined, 40 are represented only by the macropterous form; 2, 3, 5, and 6 species, by macropterous and brachypterous, macropterous and micropterous, micropterous, and apterous forms, respectively.