Changes In Sex Ratio Research Articles

Information use and plasticity in the reproductive decisions of malaria parasites.

BackgroundInvestment in the production of transmissible stages (gametocytes) and their sex ratio are malaria parasite traits that underpin mosquito infectivity and are therefore central to epidemiology. Malaria parasites adjust their levels of investment into gametocytes and sex ratio in response to changes in the in-host environment (including red blood cell resource availability, host immune responses, competition from con-specific genotypes in mixed infections, and drug treatment). This plasticity appears to be adaptive (strategic) because parasites prioritize investment (in sexual versus asexual stages and male versus female stages) in manners predicted to maximize fitness. However, the information, or ‘cues’ that parasites use to detect environmental changes and make appropriate decisions about investment into gametocytes and their sex ratio are unknown.MethodsSingle genotype Plasmodium chabaudi infections were exposed to ‘cue’ treatments consisting of intact or lysed uninfected red blood cells, lysed parasitized RBCs of the same clone or an unrelated clone, and an unmanipulated control. Infection dynamics (proportion of reticulocytes, red blood cell and asexual stage parasite densities) were monitored, and changes in gametocyte investment and sex ratio in response to cue treatments, applied either pre- or post-peak of infection were examined.Results and conclusionsA significant reduction in gametocyte density was observed in response to the presence of lysed parasite material and a borderline significant increase in sex ratio (proportion of male gametocytes) upon exposure to lysed red blood cells (both uninfected and infected) was observed. Furthermore, the changes in gametocyte density and sex ratio in response to these cues depend on the age of infection. Demonstrating that variation in gametocyte investment and sex ratio observed during infections are a result of parasite strategies (rather than the footprint of host physiology), provides a foundation to investigate the fitness consequences of plasticity and explore whether drugs could be developed to trick parasites into making suboptimal decisions.

Abstract W P145: Shift in Sex Ratio Over Time in Cerebral Venous Thrombosis

Background: In contemporary studies on cerebral venous thrombosis (CVT) there is a predominance of female patients. The change in sex ratio over time, however, has not been systematically studied Methods: We performed a systematic review of the literature up to April 2013. Studies with ≥ 40 CVT patients that reported outcome were eligible. Pediatric studies, studies which selectively included women and those in which no sex ratio was reported were excluded. We ranked studies according to the year halfway the period of patient inclusion. If no time span was reported, we assumed a period of inclusion of 10 years prior to the year of publication. Results: Fifty-three studies, with a total of 20.881 patients were included. The mean age was 36 years (SD 4.7) and 71% of patients were women. In studies that reported gender specific risk factors, 25% had a pregnancy related CVT and 37% used oral contraceptives at the time of diagnosis. There was a significant correlation between the period of the study and the percentage of women (Pearson correlation coefficient 0.37, p=0.006, figure). Similarly, there was a significant increase of oral contraceptive use among female patients, from a mean of 14% in studies before 1970 to a mean of 39% in those after 2001 (correlation coefficient 0.34, p=0.05). In contrast, the percentage of pregnancy related CVT cases did not increase over time (correlation coefficient 0.01, p=0.96). Conclusions: The sex ratio among CVT patients has significantly shifted over time, with a gradual increasing percentage of women. Our results suggest that this change is related to the increased proportion of women using oral contraceptives.

Population relevance of toxicant mediated changes in sex ratio in fish: An assessment using an individual-based zebrafish (Danio rerio) model

Ecological risk assessments (ERAs) of toxicants are predominantly based on data from laboratory tests on individuals. However, the protection goal is generally at the population level. Ecological modelling has the potential to link individual-level effects to population-level outcomes. Here we developed an individual-based zebrafish population model to study the possible population-level relevance of toxicant-mediated changes in sex ratio. The model was structured with sub-models based on empirical data (e.g. growth, reproduction, mortality) derived from a combination of our own laboratory and field experiments, the literature and theoretical concepts. The outputs of the default model were validated against size distributions for wild populations of zebrafish sampled in Bangladesh. Sensitivity analysis showed that population abundance was most sensitive to changes in density-dependent survival and the availability of refugia for juveniles.The model was then used to determine the population-level relevance of changes in sex ratio caused by an androgenic (dihydrotestosterone) and oestrogenic (4-tert-octylphenol) substance. Both were investigated under acute (10 day) and chronic (1 year) exposure regimes. Acute exposures to the test chemicals had little effect on population-level endpoints at any of the concentrations tested. Chronic exposures decreased population abundance at higher concentrations for both chemicals and most strongly with DHT. However, these concentrations were far in excess of environmentally realistic levels. Our study demonstrated that ecological models can be applied to link laboratory derived ecotoxicity data at the individual level to impacts at the population level and in our study we found different modes of action and potencies caused different levels of population perturbation. Ecological models can therefore help in assessing the ecological relevance of different organism-level effects of toxicants aiding future environmental protection strategies.

Individual and sexual identification for the wild black muntjac (Muntiacus crinifrons) based on fecal DNA

The black muntjac (Muntiacus crinifrons), endemic to China, was categorized as a Grade I National Key Protected Animal by the Ministry of Agriculture of China and classified as Vulnerable (VU) by IUCN. Recent years, studies had been conducted on this species mainly focusing on habitat selection, food habit, gene flow etc., only with a few reports on the population dynamics. Individual identification of wild animals is one of the most important subjects in the population dynamic research. Of various molecular markers, microsatellite DNA fingerprinting has been used most frequently and successfully on many kinds of animals. Here, we constructed identification system for the black muntjac using 8 microsatellite loci. 31 black muntjacs were identified from 141 fecal samples, whereas 43 samples could be used for PCR after repeated trials. Further, the sequencing for Cytb gene was also conducted for convincing us the identity of fecal samples. The results, highly consistent between sequencing consequence and sequence data from Genebank, implied that those experienced local people are of the convincing knowledge about wild animals, especially at the respects of identification to black muntjac’ feces pellets. Moreover, we detected the specificity of identification system to black muntjac. BM1225 was the only one locus that unsuccessful PCR for the muscle samples of Muntiacus reevesi was observed, which suggested that our identification system could be used for excluding the non-researched objects in some cases. Analyses using softwares CERVUS 3.0 and POPGENE 1.21 showed that the present identification system had strong discrimination power: 0.938 per loci (DP) or 0.999 in total (CDP). The mean observed number of alleles (Na), mean effective number of alleles (Ne), and mean excepted heterogosity (He) were 8.875, 6.375, and 0.829 respectively. Considering that the change of sex ratio in population could exert significant impact on population growth, density to some extent, we also analyzed the sex ratio of those individuals that had been identified based on fecal samples from filed using SRY (Sex-determining region Y) gene amplification, which identified 19 males and 12 females.

The influence of female literacy on the sex ratio in Indian states

Background: Son preference has resulted in a lopsided sex ratio in India. There is also an interregional variation in the sex ratios among the states. Aims & Objectives: This study is conducted to evaluate the influence of female literacy on sex ratios through three decades from 1981 to 2011. Materials and Methods: Data from the past four censuses were analyzed to determine the decadal change in female literacy and sex ratios in 24 states and the results were utilized to determine the impact of improving female literacy on the sex ratio in the states. Results: Female literacy in India improved from 29.85% in 1981 to 65.45 in 2011. In the same period the sex ratio improved from 934 to 943. The change in sex ratio and female literacy rates in individual states however is not uniform and there is significant regional variation. Conclusion: Female literacy has a positive bearing on the sex ratio and states which have a higher literacy rate show faster movement towards gender parity. Therefore higher the female literacy rate in a state more is the improvement in sex ratio for every percent further rise in female literacy.

Sex-Selective Abortion Bans are Not Associated with Changes in Sex Ratios at Birth Among Asian Populations in Illinois and Pennsylvania

Legal prohibitions on sex-selective abortions are proliferating in the United States. Eight state legislatures have banned abortions sought on the basis of the sex of the fetus, 21 states have considered such laws since 2009, and a similar bill is pending in U.S. Congress. These laws have been introduced and enacted without any empirical data about their impact or effectiveness. Prior studies of U.S. Census data found sex ratios among foreign-born Chinese, Korean and Indian immigrants were skewed in favor of boys, but only in families where there were already one or two girls. Using the variation in the timing of bans in Illinois and Pennsylvania as natural experiments, we compare the pre-ban and post-ban sex ratios of certain Asian newborn children in these states over 12-year periods. We then compare these ratios with the sex ratios of Asian newborn children in neighboring states during the same period. We find that the bans in Illinois and Pennsylvania are not associated with any changes in sex ratios at birth among Asians. In Illinois and its neighboring states, the sex ratio at birth of Asian children was not male-biased during our study period. On the other hand, the sex ratio at birth among Asians in Pennsylvania and its neighboring states was skewed slightly in favor of boys, but the enactment of the ban did not normalize the sex ratio. This strongly suggests that sex-selective abortion bans have had no impact on the practice of sex selection, to the extent that it occurs, in these states. This finding is highly relevant to legislative and policy debates in the U.S. Congress and state legislatures where sex-selective abortion laws are being considered.

“No one says ‘No’ to money” – a mixed methods approach for evaluating conditional cash transfer schemes to improve girl children’s status in Haryana, India

IntroductionHaryana was the first state in India to launch a conditional cash transfer (CCT) scheme in 1994. Initially it targeted all disadvantaged girls but was revised in 2005 to restrict it to second girl children of all groups. The benefit which accrued at girl attaining 18 years and subject to conditionalities of being fully immunized, studying till class 10 and remaining unmarried, was increased from about US$ 500 to US$ 2000. Using a mixed methods approach, we evaluated the implementation and possible impact of these two schemes.MethodsA survey was conducted among 200 randomly selected respondents of Ballabgarh Block in Haryana to assess their perceptions of girl children and related schemes. A cohort of births during this period was assembled from population database of 28 villages in this block and changes in sex ratio at birth and in immunization coverage at one year of age among boys and girls was measured. Education levels and mean age at marriage of daughters were compared with daughters-in-law from outside Haryana. In-depth interviews were conducted among district level implementers of these schemes to assess their perceptions of programs’ implementation and impact. These were analyzed using a thematic approach.ResultsThe perceptions of girls as a liability and poor (9% to 15%) awareness of the schemes was noted. The cohort analysis showed that while there has been an improvement in the indicators studied, these were similar to those seen among the control groups. Qualitative analysis identified a “conspiracy of silence” - an underplaying of the pervasiveness of the problem coupled with a passive implementation of the program and a clash between political culture of giving subsidies and a bureaucratic approach that imposed many conditionalities and documentary needs for availing of benefits.ConclusionThe apparent lack of impact on the societal mindset calls for a revision in the current approach of addressing a social issue by a purely conditional cash transfer program.

Changes in age and sex ratios amongst samples of hunter-shot wings from common duck species in Denmark 1982–2010

There are almost no long-term demographic monitoring programmes of commoner waterbird species, yet such data are fundamental to our understanding of drivers of population change. In the present study, we present annual age and sex ratios in samples of shot duck wings forwarded on a voluntary basis by hunters throughout Denmark from 1982 to 2010 for eight common quarry species. Wigeon, Shoveler, Pintail and Goldeneye showed statistically significant declines in the proportions of young birds in the samples, but only Wigeon showed a statistically significant decline in the proportion of females in the adult sample over this period. Amongst Wigeon, the proportions of first winter birds and females were lower amongst the sample shot over decoys compared with those shot without decoys, suggesting these two shooting methods differentially select for young birds and females. However, the slopes of declines in these proportions shot with and without decoys over time did not differ. We found no correlations between North Atlantic Oscillation index values and the proportions of young for any of the species or between May and June temperatures on the breeding areas of Wigeon and the proportions of young in samples derived the following winter. With the exception of Wigeon, little is known about how well the shot duck wing samples reflect the true ratios in the populations, and unravelling the error and bias associated with these samples remains a high future research priority. If long-term declines in age and sex ratio in the wing surveys reflect true trends in the Wigeon population as a whole, we have strong grounds for concern for this population, and effort should be invested in increased demographic surveillance to better understand the causes of these changes. We need improved methods to derive unbiased measures of annual breeding of our common duck species if we are to be better able to understand the population dynamics of these stocks and be effective in their management. In the meantime, the Danish wing survey represents a unique time series of reproductive success for many common migratory duck species and must be maintained and further exploited.

Effect of manipulated sex ratio on insemination of the red mason bee Osmia bicornis L. under net cage conditions

Abstract The red mason bee Osmia bicornis L. (Hymenoptera: Megachilidae) is a solitary gregarious species that is known to be a good pollinator of pear, apple, and several other Rosaceae fruit plants. Mainly females are active in plant pollination, and therefore they are of strong interest to farmers. As natural populations are usually male biased, here we studied the possibility of rearing a female-biased population of Osmia bicornis by examining the effects of sex ratio changes on female survival, insemination rate, and sperm count in the spermatheca. Using bees that had completed their winter diapause and were maintained in flying cages, we created three groups with different male:female sex ratios: 1:1, 1:2, and 1:3. The 1:3 sex-ratio group exhibited the best survival of females, but the lowest spermathecae sperm count. The insemination rate did not differ between groups. Our results indicate that-at least among bees housed in isolator cages for plant breeding- skewing the sex ratio towards more females does not affect bee survival, and efficient insemination can be expected with twice as many females as males.

Who Make Effective Teachers, Men or Women? An Indian Perspective

The article aims to discuss the effectiveness of male and female teachers in relation to demographic factors like marital status, training, location and medium of instruction. These issues have important implications to understand and evaluate teachers' effectiveness especially in view of the changing sex ratio of school teachers. Correlation, t-test, and ANOVA were employed on a sample of 482 teachers comprising 245 males and 237 females. Overall, male and female teachers exhibited insignificantly different effectiveness however variations were noticed with respect to different demographic factors. The paper concludes by arguing that since the quality of education being delivered, generally, has been considered as a function of teachers' degree of effectiveness, there is a need for both substantive and methodological focus on gender specific responsibilities and requirements, in order to take out maximum from male and female teachers to produce high degree of effectiveness in their profession.

Could changes in reported sex ratios at birth during China's 1958-1961 famine support the adaptive sex ratio adjustment hypothesis?

AbstractBACKGROUNDThe adaptive sex ratio adjustment hypothesis suggests that when mothers are in poor conditions sex ratio of their will be biased towards females. Major famines provide opportunities for testing this hypothesis they lead to widespread deterioration of living conditions in affected population.OBJECTIVEThis study examines changes in sex ratio at birth before, during, and after China's 1958-1961 famine, to see whether they provide any support for adaptive sex ratio adjustment hypothesis.METHODSWe use descriptive statistics to analyse data collected by both China's 1982 and 1988 fertility sample surveys and examine changes in sex ratio at birth in recent history. In addition, we examine effectiveness of using different methods to model changes in sex ratio at birth and compare their differences.RESULTSDuring China's 1958-1961 famine, reported sex ratio at birth remained notably higher than that observed in most countries in world. The timing of decline in sex ratio at birth did not coincide with timing of famine. After famine, although living conditions were considerably improved, sex ratio at birth was not higher but lower than that recorded during famine.CONCLUSIONThe analysis of data collected by two fertility surveys has found no evidence that changes in sex ratio at birth during China's 1958-1961 famine and post-famine period supported adaptive sex ratio adjustment hypothesis.1. IntroductionTrivers and Willard proposed a major hypothesis in study of sex ratios in 1973. The hypothesis suggests that because reproductive success of male tends to be more variable and resource-sensitive than that of female offspring (Song 2012: 1), natural selection should favour parental ability to adjust sex ratio of produced according to parental ability to invest (Trivers and Willard 1973: 90). This kind of adjustment or control can take place both before and after birth. Accordingly, when maternal condition declines, mothers tend to produce a lower ratio of males to females (Trivers and Willard 1973: 90; also Cronk 2007). This hypothesis, also referred to as adaptive sex ratio adjustment hypothesis, has been tested by several studies of human populations in recent years, although results have been mixed (Keller et al. 2001; Lazarus 2002; Gibson and Mace 2003; Stein et al. 2004; Cronk 2007).In a recent paper published by Proceedings of Royal Society B, which is entitled Does famine influence sex ratio at birth? Evidence from 1959 -1961 Great Leap Forward Famine in China?, Shige Song examined impact of this famine on changes in sex ratio at birth (SRB) through analysing data collected by China?s 1982 National One-Per-Thousand Population Sample Survey. According to author, the study identified an abrupt decline in sex ratio at birth between April 1960, over a year after Great Leap Forward Famine began, and October 1963, approximately 2 years after famine ended, followed by a compensatory rise between October 1963 and July 1965. These findings support adaptive sex ratio adjustment hypothesis that mothers in good condition are more likely to give birth to sons, whereas mothers in poor condition are more likely to give birth to daughters (Song 2012: 1). Song?s paper has been publicized widely. In commenting on Song?s results, Nature reported in its news section that Hungry mothers give birth to more daughters (Corbyn 2012). LiveScience, a major science website, also reported that Hard times mean fewer baby boys (Pappas 2012).In this paper, using data collected by both China?s 1982 National One-Per- Thousand Population Sample Survey on Fertility and 1988 National Sample Survey on Fertility and Contraception, we further examine changes in reported SRB during China?s 1958-1961 famine. …

Male-Killer Dynamics in the Tropical ButterflyAcraea encedon(Lepidoptera: Nymphalidae)

Sex ratio distortion in the tropical butterfly Acraea encedon is caused by infection with a male-killing bacterium of the genus Wolbachia. Severely female-biased populations with extremely high bacterial prevalences were previously reported in A. encedon. In this paper, we describe a study in which the spatial variations and the temporal changes in the population sex ratio and the prevalence of the male-killing Wolbachia were thoroughly investigated in the wild populations of Acraea encedon in Uganda between 2005 and 2007. The two parameters were found to vary extensively over space and time, indicating that the male-killer is highly dynamic. Both the female-bias and the Wolbachia prevalence were lower than that recorded in the literature.

Changes in sex ratios of a dioecious grass with grazing intensity: the interplay between gender traits, neighbour interactions and spatial patterns

Summary Dioecious plants frequently face sex‐related resource allocation trade‐offs. Differential traits of male and female plants can have important consequences that influence their direct and indirect interactions with neighbours and herbivores. Gender differences in traits have been considered to be inherently linked to sex‐biased ratios along environmental stress gradients. However, the mechanisms behind the variation in sex ratios with increasing biotic stress remain elusive. We linked the results of process‐based field experiments with fine‐scale spatial patterns of naturally established plants (both sexes) at different grazing intensities. We demonstrated that slow‐growing females were better defended against insects and small mammals but were more susceptible than males to competition from neighbours. In large‐herbivore exclosures, we found that sex‐biased spatial patterns at the microsite scale can be predicted from gender‐specific traits, with females more segregated from competitors (unpalatable grasses) than males. Traits related to growth/defence trade‐off in females, coupled with their higher competition costs than males, suggest that gender dimorphism in traits can directly influence species interactions and spatial organization. In the presence of large herbivores, female individuals were preferentially browsed despite their larger investment in antiherbivore compounds. The greater distance of females from unpalatable competitors was the main determinant of female‐biased consumption by domestic herbivores. Females growing close to neighbours successfully eluded browsing but also faced competition. Scaling up to a population level, population sex ratios drift from female‐ to male‐bias with increasing domestic grazing intensity. Synthesis: The sexual dimorphism in traits of a dioecious bunchgrass results in differential herbivory by natural enemies, differential competitive ability and differential spatial distribution of sexes. Domestic grazers disrupt this balance by shifting species interactions and their spatial organization. Changes in dioecious plant populations towards male‐biased sex ratios with grazing intensity could not be predicted solely by gender‐specific traits.

Mortality in patients with multiple sclerosis

Mortality in patients with multiple sclerosis (MS) is significantly increased compared with the general population. Many questions concerning survival in MS are still unanswered due to the difficulty of comparing information collected at different times and in different geographic areas. The increasing incidence of MS, the improvement in care of the chronically disabled, and different methodologies may explain the lack of coherence among studies' results. Reported times to death from birth and from disease onset/diagnosis are highly variable. Patients older at onset or with primary progressive course have shorter survival; however, data on sex and mortality are contradictory. Changes in sex ratio in MS over time represent one possible explanation. MS is the main cause of death in ≥50% of patients and the incidence of deaths not due to MS varies among countries. Particularly, suicide is substantially increased in patients with MS, and, despite its varying incidence, mainly due to "cultural bias," it should be considered an MS-related cause of death. Recent results of the long-term follow-up study of interferon-β-1b demonstrated a significant reduction of mortality among treated patients. Notwithstanding its long latency, mortality is therefore an unambiguously valid long-term outcome in randomized controlled trials. It usefully combines the net impact of treatment efficacy on longevity and adverse events, which may reduce it.

Impact of earthquakes on sex ratio at birth: Eastern Marmara earthquakes

Previous reports suggest that maternal exposure to acute stress related to earthquakes affects the sex ratio at birth. Our aim was to examine the change in sex ratio at birth after Eastern Marmara earthquake disasters. This study was performed using the official birth statistics from January 1997 to December 2002 - before and after 17 August 1999, the date of the Golcuk Earthquake - supplied from the Turkey Statistics Institute. The secondary sex ratio was expressed as the male proportion at birth, and the ratio of both affected and unaffected areas were calculated and compared on a monthly basis using data from gender with using the Chi-square test. We observed significant decreases in the secondary sex ratio in the 4th and 8th months following an earthquake in the affected region compared to the unaffected region (p= 0.001 and p= 0.024). In the earthquake region, the decrease observed in the secondary sex ratio during the 8th month after an earthquake was specific to the period after the earthquake. Our study indicated a significant reduction in the secondary sex ratio after an earthquake. With these findings, events that cause sudden intense stress such as earthquakes can have an effect on the sex ratio at birth.

Manipulation of Primary Sex Ratio in Birds: Lessons from the Homing Pigeon (Columba livia domestica)

Across various animal taxa not only the secondary sex ratio but also the primary sex ratio (at conception) shows significant deviations from the expected equal proportions of sons and daughters. Birds are especially intriguing to study this phenomenon as avian females are the heterogametic sex (ZW); therefore sex determination might be under direct control of the mother. Avian sex ratios vary in relation to environmental or maternal condition, which can also affect the production of maternal steroids that in turn are involved in reproduction and accumulate in the developing follicle before meiosis. As the proximate mechanisms underlying biased primary sex ratio are largely elusive, we explored how, and to what extent, maternal steroid hormones may be involved in affecting primary or secondary sex ratio in clutches of various species of pigeons. First we demonstrated a clear case of seasonal change in sex ratio in first eggs both in the Rock Pigeon (Columba livia) and in a related species, the Wood Pigeon (Columba palumbus), both producing clutches of two eggs. In the Homing Pigeon (Columba livia domestica), domesticated from the Rock Pigeon, testosterone treatment of breeding females induced a clear male bias, while corticosterone induced a female bias in first eggs and we argue that this is in line with sex allocation theory. We next analyzed treatment effects on follicle formation, yolk mass, and yolk hormones, the latter both pre- and post-ovulatory, in order to test a diversity of potential mechanisms related to both primary and secondary sex ratio manipulation. We conclude that maternal plasma hormone levels may affect several pre-ovulatory mechanisms affecting primary sex ratio, whereas egg hormones are probably involved in secondary sex ratio manipulation only.

Seasonal Variation in Offspring Sex Ratio in the Snowy Plover

The Snowy Plover (Charadrius nivosus) is unique in being a determinate layer of an odd modal clutch size and in having a variable mating system in which female brood desertion occurs regularly. These traits make determining Snowy Plover offspring sex ratios important not only for long-term population stability, as the species is of conservation concern, but also for application to sex allocation theory. In this study, we determined Snowy Plover offspring sex ratios, examined differential costs of producing male and female offspring, and evaluated sex ratio variation in relation to maternal condition, habitat condition, and time during the nesting season on saline lakes of the Southern High Plains of Texas. Examination of 245 chicks from 118 clutches during 1999–2000 and 2008–2009 showed that male offspring were more costly to produce than female offspring; however, offspring sex ratio did not differ from parity, but was slightly male-biased in most years. The probability of producing a male offspring was greater both earlier and later in the breeding season than in the middle. As the availability of saline lake surface water and the subsequent availability of food vary unpredictably throughout the breeding season, depending on precipitation events, we suggest that sex ratio adjustment in unpredictable environments may not be straightforward and may follow nonlinear models and/or vary annually The effects such changes in sex ratios may have on population growth and stability remain unknown.

War and the political zeitgeist: Evidence from the history of female suffrage

Despite the upheaval associated with warfare, empirical evidence linking conflict with institutional development is limited. This paper examines the hypothesis that international wars accelerated democratization by fostering political inclusion. Employing survival analysis, I find that during the 20th century, nations engaging in external conflict were more than twice as likely to extend the franchise to women in the post-conflict period, even after controlling for other commonly cited determinants of suffrage adoption. I explore several potential mechanisms for this association and find evidence consistent with stories which connect war with increased national unity, ideological fervor, and international posturing. Finally, examining conflict-induced changes in sex ratios and female labor force participation suggests that the underlying determinants of suffrage expansion at the national and sub-national level differ.

The functional and numerical responses ofTrissolcus basalis(Hymenoptera: Platygastridae) parasitizingNezara viridula(Hemiptera: Pentatomidae) eggs in the field

Trissolcus basalis has been used as a biological control agent of its main host, Nezara viridula, in many countries. However, estimations of its functional and numerical responses in the field are lacking. We estimated the density of N. viridula eggs, the proportion of parasitized N. viridula eggs, and the number of T. basalis adults/trap in the field. We transformed relative parasitoid density to an absolute density, and estimated the parasitoid's attack rate, a, and the mutual interference parameter, m, in two ways: following Arditi & Akçakaya (1990) and using the Holling-Hassell-Varley model with two iterative techniques. The attack rate estimated by both methods were a=1.097 and a=0.767, respectively. Parameter m varied less between methods: m=0.563 and m=0.586, respectively, and when used to calculate the number of parasitized N. viridula eggs per m2, differences with the observed values were not significant. The numerical response of T. basalis was affected by the sex allocation of their progeny and the proportion of adult parasitoids trapped decreased with field parasitoid population density. Theoretical models show that 0<m<1 is a stabilizing factor and previous re-analysis of field data showed a mean m value of 0.8. The Holling-Hassell-Varley model leads to a flexible description of the functional response allowing to predict acceptable weekly host parasitism. The pre-imaginal parasitoid survival and the change in sex ratio as a function of parasitoid density adequately describe the numerical functional response of the parasitoid.

A Study about Awareness Regarding Pre-Natal Sex Determination and Gender Preference among Antenatal Women in Rural Bangalore

Background: The preference for son and discrimination against the girl child is almost universal in India and manifest it in many ways. Changes in sex ratio reflect underlying socioeconomic, cultural patterns of a society. Skewed sex ratio is an issue of major concern. Desire for male child manifests so blatantly that parents have no qualms about repeated, closely spaced pregnancies, premature deaths and even terminating child before it is born. Method: Total 200 antenatal women were interviewed by systematic random sampling with prior consent using a well designed, pre- tested questionnaire. The data was analyzed by percentages and chi-square test Results: Overall in this study it was observed male preference was in 63% antenatal women. Out of total women with first child as a baby girl 78.6 % keenly wanted second baby as a boy. Almost more than half of the women (59%) were aware about consequences of female foeticide and 69% were aware of the PNDT act.