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

Summary 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.     

Reproductive strategy of insects as adaptation to temporally varying environments

Summary Diversity of oviposition curve observed in 125 insects was analysed using the ratio of the length of period for development to that for reproduction. On the basis of this empirical data, two extreme reproductive patterns were selected: prolonged reproduction with early maturity and concentrated reproduction with late maturity. Population growth of the species with each reproductive pattern was calculated usingLeslie Matrix under some simulated fluctuating environments where the length of time during which the environments change is short compared with the time required to stabilize age structure. These simulation studies show that there is an optimal ratio of the length of period for development to that for reproduction in achieving high population densities and this ratio varies depending on the favorableness of environment for reproductive success: as the environmental favorableness decreases, the optimal ratio becomes larger.     

Does Late Reproduction Extend the Life Span? Findings from European Royalty

Statistical associations between late reproduction and female longevity led to speculations that a late birth increases a mother's life span. The database used here includes all descendants of King George I of England (1660–1727) and his wife, Sophie Dorothea (1666–1726), born in the royal dynasties in Europe up to 1939 (n=1,672). In the era of British world supremacy, these descendants formed the uppermost layer of the European aristocracy, occupying all royal thrones from 1850 onward. Novel in this study is the use of pedigree information. In pairs of ever‐married full sisters (brothers), both surviving to 45 (50) years, both having at least one child, the study examines whether the sibling with the first—or last—child born later in life also lived a longer life. This design controls for genetics, socioeconomic status, parity, social support, child mortality, birth cohort, and various environmental factors. In the 157 pairs of sisters and 191 pairs of brothers, later reproduction did not extend the life span.     

Maternal age as a source of variation in the ability of an aphid to produce dispersing forms

Summary Apterous parthenogentic females of the pea aphid,Acyrthosiphon pisum (Harris), begin to produce alate offspring soon after they have been subjected to crowding. Females which were born early in their own parent's reproductive period respond most strongly to crowding, producing much larger numbers of alatae than their late-born sisters. In contrast, the early-born daughters of most alate females do not produce winged offspring after being crowded. Some of their later-born sisters may produce a few winged individuals, resembling in this respect the late-born daughters of the apterous females. Control of the production of alatae thus begins in the grandparental generation. Risk-spreading by means of differential dispersal becomes a less uncertain venture when local populations can modify their responses to environmental changes by utilizing past as well as present signals from their surroundings.     

Parental age and offspring mortality: Negative effects of reproductive ageing may be counterbalanced by secular increases in longevity

As parental ages at birth continue to rise, concerns about the effects of fertility postponement on offspring are increasing. Due to reproductive ageing, advanced parental ages have been associated with negative health outcomes for offspring, including decreased longevity. The literature, however, has neglected to examine the potential benefits of being born at a later date. Secular declines in mortality mean that later birth cohorts are living longer. We analyse mortality over ages 30–74 among 1.9 million Swedish men and women born 1938–60, and use a sibling comparison design that accounts for all time-invariant factors shared by the siblings. When incorporating cohort improvements in mortality, we find that those born to older mothers do not suffer any significant mortality disadvantage, and that those born to older fathers have lower mortality. These findings are likely to be explained by secular declines in mortality counterbalancing the negative effects of reproductive ageing.     

Extraordinary effects of fertilization status on the reproduction of an arrhenotokous and sub-social spider mite (Acari: Tetranychidae)

Summary Experimental observations on the arrenotokous reproductive patterns of two spider mite species (Acari: Tetranychidae), the long-seta form ofSchizotetranychus celarius (Banks) andTetranychus urticae Koch, revealed that reproduction of unfertilized females of the former is very differnt from that of the latter. Unfertilized females ofS. celarius, which has a subsocial life, laid a few eggs and then became inactive. In contrast, the fecundity of unfertilizedT. urticae females was only slightly reduced as compared with fertilized females. Mother-son matings may thus sometimes occur in naturalS. celarius populations. A two-year field survey revealed that, in the absence of males, overwintering females ofS. celarius occasionally remain unfertilized until early spring. Furthermore, nest foundation observed in late spring indicated that most of the season's first nests were founded by single females. These two sets of observations strongly suggest that motherson mating takes places in nature, corresponding to the reproductive trait seen in the experiment. Mother-son mating inevitably increases the relatedness between nest members. The estimated father's relatedness to its offspring is extraordinarily high under such condition. The possibility that kin-selection in the long seta-form ofS. celarius led to subsociality, especially paternal care, is suggested. This study was supported in part by Grant-in-Aid No. 61540468 from the Ministry of Education, Science and Culture, Japan.     

Longevity, flight ability and reproductive performance of the diamondback moth,Plutella xylostella (L.) (Lepidoptera: Yponomeutidae), related to adult body size

Plutella xylostella in the temperate zone shows a clear seasonal change in adult body size. In the laboratory, large and small moths were produced during immature stages at 15°C and 25°C, respectively. These moths were then used to evaluate longevity, age-specific flight ability, flight ability of mated and unmated females, and the influence of flight experience on the subsequent reproductive success. The large moths lived longer and displayed a greater flight ability over 3 weeks. Irrespective of body size, unmated females flew for a longer time than mated females, and flight experience affected their subsequent reproductive success. Females of both sizes mated and laid eggs soon after emergence, without any obvious pre-reproductive period. More flight experience did not delay oviposition, but did reduce egg production. It is likely that large moths with a longer adult life span and greater flight ability are better fitted for long-distance flight and more fecund than small ones. These experimental results may explain why long-distance migration ofP. xylostella is mostly seen during cool seasons, when relatively large moths with long forewing appear in the field.     

Sex preference versus number preference: the case of Korea

The author argues that the effect of sex preference must be disentangled from the effect of number preference in Korea. This study tests--with hazard models--the effect of the number of previous children on the next birth according to the sex composition of previous children. Data were obtained from the 1974 Korean Fertility Survey. This paper also analyzes the timing of childbearing in recent periods in order to determine whether replacement-level fertility is temporary or permanent. The ideal number of children declined from 3.9 children in 1965 to 2.1 in 1991. The age-specific fertility rates for ages 20-24 years declined rapidly during the late 1980s. The fertility rates among women aged 25-29 years and 30-34 years increased during 1985-90. The proportion of fertility among women aged 20-29 years increased from 67.9% in 1975 to 86.6% in 1984. Women born in the late baby boom period of the late 1950s to mid-1960s reached prime reproductive age during the late 1980s and 1990s, but the crude birth rate remained about the same during 1985-92. A higher percentage of women (22.4%) born during 1955-59 remained single in 1990. During 1960-90, the percentage of women aged 20-24 years who were married declined. These trends indicate later age at childbearing and an explanation for the temporary nature of below-replacement fertility in the late 1980s. Korean women did not want to have more than 2 children, and the interval between first and second births increased since 1985. Among pregnancies of parity 2 conceived since 1985, over 90% of women with at least one son ended subsequent pregnancies by abortion compared to only 59% without sons. Hazard models of 1974 data reveal that son preference had an important effect on fertility. Fertility was higher among women with only daughters. Findings suggest that the value of sons must be measured at the societal and not at the individual level.     

The effects and limits of territoriality on population regulation in grey red-backed voles,Clethrionomys rufocanus bedfordiae

Summary The effects of breeding territoriality on the stability of grey red-backed vole (Clethrionomys rufocanus bedfordiae) populations were investigated on a control grid and a grid on which the voles were fed, in an outdoor enclosure in Hokkaido, Japan. Vole populations were monitored by live trapping from 1984 to 1986: (1) Population density was 2–7 times greater on the experimental grid to which food was added than on the control grid. Reproductive output was more closely associated with the difference in density between grids than survival or dispersal (immigration and emigration) rates. (2) The number of adult females and pregnancy rate of the experimental population were significantly greater than those of the control one. The difference in the number of adult females between the populations was greater than that in pregnancy rate. (3) The proportion of successful litters and the number of weanlings per litter were not significantly different between the control and experimental population. (4) Adult females held territories on both the control and experimental grid; they were spaced out more than would be expected from random occupation. The territories overlapped more on the experimental grid than on the control grid. (5) Mean territory size of adult females on the experimental grid was about half of that on the control grid. The territory size was correlated negatively with population density. (6) The proportion of trap sites that were used by adult females was significantly greater on the experimental grid than on the control grid. This suggests that adult females on the experimental grid used the area more extensively. This factor, in association with territory size and overlapping of territory, was also important in causing the difference in the number of adult females between the grids. (7) These results call into question the hypothesis that territoriality stabilizes the density in populations ofClethrionomys.     

Sexual differences in natal dispersal and philopatry of the grey-sided vole

The natal dispersal distance of the grey-sided vole,Clethrionomys rufocanus (Sundevall), was measured in a large outdoor enclosure (2.1 ha) in Hokkaido, Japan. Voles in about half of the enclosure (1 ha) were fed. Distance from the natal site to the site of reproduction was significantly greater in males (64.9 m) than in females (35.3 m). In males, 24.8% settled within one home range length of their natal site and 49.6% settled further than two range lengths from their natal site. In femles, the respective percentages were reversed: 51.2% and 22.0%. The timing of large movements (≥50 m) was related to body mass in both sexes. The population density was always higher on the fed grid than on the control grid, which resulted in the frequency of large movements being greater on the fed grid that on the control grid. Thus, the percentage of voles performing a large movement was not different between the grids in both sexes.     

Selection and reproductive success in males of the dragonfly,Orthetrum japonicum (Odonata: Libellulidae)

Reproductive success, copulation success, and mating success were measured for a population of male dragonflies,Orthetrum japonicum. Copulation success explained the greatest variation in reproductive success. The proportion of copulations followed by oviposition was positively correlated with the number of oviposited eggs per mating. Directional selection on four morphological characters was estimated. The effect of selection on correlated traits was comparable to that of direct selection. Directional selection varied between traits and between episodes in a single trait. The probability that the observed directional selection on the four morphological traits was expected under the condition of the selective neutrality of traits was not smaller than 5%.     

The Contribution of Assisted Reproduction to Completed Fertility: An Analysis of Danish Data

Assisted reproduction has a minor but increasing influence on childbearing trends in advanced societies. In Denmark, the use of assisted reproduction technology (ART) has become particularly widespread. At the same time, Danish women born in the late 1950s and the 1960s experienced stabilization or even a slight increase in their mean number of children. Broad availability and widespread use of assisted reproduction may become important factors contributing to maintaining relatively high completed fertility among the younger cohorts of Danish women. To explore this idea, we analyze and project cohort trends in fertility rates among native Danish women born in 1960‐78 and examine the likely contribution of assisted reproduction to these trends. The projected proportion of children born after ART treatment shows a substantial increase from 2.1 percent among women born in 1965 to 4‐5 percent among women born in 1978, with an estimated net impact of ART (as compared with the hypothetical situation where no ART treatment was available) on the order of 3‐4 percent. When intrauterine inseminations are included, this implies that up to 7 percent of children of those native Danish women born in 1975 and later will likely be conceived by infertility treatment.     

Reproductive mobilities

ABSTRACT

This special issue brings reproduction into a critical mobilities framework. We extend scholarship in cross-border reproductive care and medical mobilities into new theoretical and empirical directions. Reproductive mobilities articulates the mutual constitution of reproduction and mobilities. Human (and nonhuman) movement not only shapes reproduction but produces reproductive imaginaries, desires, futures, trajectories, as well as the subjectivities and ‘becoming-ness’ of diverse reproductive subjects. Through the lens of reproduction, we examine how contemporary mobilities—and immobilities—intersect with gendered, racialized, sexually expressive, nation-inscribed, fertile, infertile, young, aging, pregnant, surrogate, and/or otherwise non/reproductive bodies and persons. Can human reproduction be analyzed without noticing all things mobile and immobile that converge to construct reproductive (and non-reproductive) desires and practices? Can mobility and immobility be considered without thought to how worlds and worlding comes about? Mobility facilitates reproduction, and new possibilities for reproduction; reproduction is mobile at scales from the molecular to the transnational. This effort to bring the fields of reproduction and mobilities into dialogue does not introduce a new sub-field but rather creates the opening for a trajectory of empirical work and theoretical ideas that invigorates mobilities with newfound attention on the matter and becoming-ness of reproduction.     

Mating and diapause in hibernating adults ofMenida scotti puton (Heteroptera: Pentatomidae)

InMenida scotti aduts which mate during hibernation, we examined the effect of photoperiod on diapause induction in terms of the developmental degree of reproductive organs and corpora allata. In a hibernating population, mating season and physiological changes related to dipause were investigated. When newly emerged adults were reared under long- or short-day conditions, reservoir of the ectodermal accessory gland and corpora allata in males developed, while the developments of ovary and corpora allata in females were suppressed under both conditions. This suggests that diapause of this species is induced only in females independently photoperiodic conditions during adult stage. In a hibernating population, mating was observed from early to late November and from late March to early May. Observations of the development of reproductive organs and corpora allata suggest that diapause is induced only in females in the former period, while both sexes are not in diapause in the latter period.     

Reproductive history and mortality later in life: A comparative study of England and Wales and Austria

Does a woman's reproductive history influence her life span? This study explores the question with data from the contemporary female populations of England and Wales and Austria. It is the first comparative study to investigate the relationship between fertility and mortality late in life. We find similar patterns and age-specific trends of excess mortality in both populations: parity significantly influences longevity, as do both an early and a late birth. These differences in longevity are not explained by differences in educational or family status. The impact of a woman's reproductive history on her life span is small, however, compared to the influence of her level of education or family status.     

Reproductive history and mortality later in life: a comparative study of England and Wales and Austria

Does a woman's reproductive history influence her life span? This study explores the question with data from the contemporary female populations of England and Wales and Austria. It is the first comparative study to investigate the relationship between fertility and mortality late in life. We find similar patterns and age-specific trends of excess mortality in both populations: parity significantly influences longevity, as do both an early and a late birth. These differences in longevity are not explained by differences in educational or family status. The impact of a woman's reproductive history on her life span is small, however, compared to the influence of her level of education or family status.     

Age specificity of inbreeding depression during a life cycle ofCallosobruchus chinensis (Coleoptera: Bruchidae)

Summary Age-specific effects of inbreeding on fecundity were assayed for adzuki bean weevilCallosobruchus chinensis by comparing inbred lines and their cross. Four consecutive full-sib matings reduced only 10.3 percent in total fecundity, and did not decrease early fecundity at all until third day from the onset of reproduction. It is suggested that recessive detrimental genes have been eliminated from the early period of adult life span when reproductive value is high. There was a slight tendency that inbreeding depression increased as age proceeded though not statistically significant.     

Beyond infant mortality: gender and stillbirth in reproductive mortality before the twentieth century

Though it has been the largest component of reproductive mortality since its statutory registration in 1928, stillbirth has received little attention from historical demographers, who have relied on the more orthodox indicator of early human survival changes - "infant mortality". The exclusion of stillbirth hampers demographic analysis, underestimates progress in newborn vitality, and over-privileges post-natal causes in theoretical explanation. A case is made for estimating stillbirth before 1928 as a ratio of early neonatal death, and for employing perinatal mortality as an historical indicator of female health status. The long-run trend of reproductive mortality (encompassing mature foetal and live born infant death during the first eleven months) reveals a substantial decline in perinatal causes in the first industrial century (1750-1850), implying a major concurrent improvement in the nutritional status of child bearers. Reproductive mortality is a more complete indicator of death in infancy. It offers demographers a means of fracturing the fertility versus mortality dualism and a potential purchase on gender as a demographic variable, while re-opening the case on mortality in the demographic dynamic of the world we have lost.     

Child mortality and reproductive behaviour in German village populations in the past: A micro-level analysis of the replacement effect

Abstract Reproductive histories of couples married during the eighteenth and nineteenth centuries in a sample of 14 German villages are analysed in order to answer several questions regarding the relationship between child mortality and reproductive behaviour. An effort is made through selection of cases and use of multiple classification analysis to eliminate or control non-volitional or otherwise confounding influences on the relationship between a couple's experience with child mortality and their fertility. The results do not provide a decisive answer to the question of whether, under a regime of otherwise presumed natural fertility, previous experience of child mortality affected subsequent reproductive behaviour. The evidence was much clearer in indicating that behaviour consistent with replacement efforts emerged or strengthened as family limitation spread. Finally, the results indicated that though it was not necessary for overall child mortality to decline before family limitation practices were adopted, couples with the most favourable child mortality experience were most likely to practise family limitation and to reduce their fertility. Child mortality appeared at least to impede, if not totally prevent, efforts to reduce the number of children ever born or to cease childbearing at an earlier age or at a given parity.     

Regulation of reproduction rate in a cyclic population of the red-backed vole,Clethrionomys rufocanus bedfordiae

Summary Changes of the components of reproduction were analyzed quantitatively in a two-year cyclic population (which has two peaks in alternate years during a five-year census) of the red-backed vole,Clethrionomys rufocanus bedfordiae, with reference to its regulatory mechanism: (1) Variation in sex ratios was not associated with population phase or density, although a higher percentage of females in mature individuals was observed in the increase phase. (2) Females attained to sexual maturity at younger age and at lighter body weight than did males. All the youngest mature individuals were found in the low and the increase phases. Age and size at maturity became older and larger as the population went toward the peak phase. (3) Maturation rate was strongly associated with population phase and density; this component is an important and good parameter to predict population trend. Maturation rates were in the order, the low phase>the increase phase>the peak phase>the decline phase; the differences in the rates among these phases were significant. Maturation rate was somewhat depressed when the population density exceeded about 40 individuals/ha. Changes in age at maturity and in maturation rate are interpreted as derivative phenomena related to the population density and the capacity of the number of mature voles per unit area. (4) The maximum number of mature individuals were 26 males/ha and 29 females/ha; there was almost no increase of the number of mature voles at higher population densities over about 40 individuals/ha. The number of exclusive home ranges per hectare calculated from the observed range lengths did not differ much from the maximum number of mature voles of either sex. (5) Length of breeding period was shorter in the high-density years than in the low-density years; the breeding started earlier and ended earlier in the former than that in the latter. In the increase phase a few voles reproduced in winter. (6) The percentage of pregnant females was significantly lower in the peak phase than those in the other phases.