Combining methods of insect pest control: Partitioning mortality and predicting complementarity

Summary An age-structured population model is used as a vehicle for presenting a method for the analysis of interactions between pairs of insect pest control methods. This analysis is based on partitioning the total mortality acting on a population into its constituent components from all known sources. Pairwise critical mortality curves are then constructed which represent the combined mortality required for eradicating the pest population. Effort curves are then constructed from computing the mortality resulting from a given amount of control effort. The convolution of the critical mortality curves and the effort curves then yields the isoclines formed by the effort required of two control methods in combination to achieve eradication. This analysis allows the prediction of either synergism or interference between the control methods and also helps explain patterns observed in previous modelling of such combinations of pest control methods.     

Modelling the effects of population aggregation on the efficiency of insect pest control

Summary A methodology is developed to assess the effects of spatial distribution on the efficiency of insect pest control. This methodology is especially applicable to pest control methods whose efficiency of action depends either positively or negatively on pest density It is applied here to the sterile insect technique and pheromone trapping for male annihilation, which both depend negatively on density. This methodology relies on quantifying clumps of various size and then relating this to efficiency of control and predicting the total pest production given the information on clump sizes and efficiency of control for each clump size. It is found that control is about four times as difficult for a population that is highly clumped (k of the negative binomial distribution=0.25) as for a regularly dispersed population.     

Models for mating disruption by means of pheromone for insect pest control

Models are presented to investigate the population dynamic behavior of a pest population with the release of pheromone for mating disruption. Three mechanisms of mating disruption are considered: (i) confusion of males, (ii) competition with female pheromone trails yielding false trail following, (iii) emigration of males prior to mating. In addition, several refinements to confusion are considered. Confusion and emigration of males were found to be very similar both quantitatively and dynamically; also, a combination of both mechanisms was very little more efficient than either one separately. False trail following is difficult to compare with the other two, since competition with wild females is involved and thus the total population size enters the equations. Density dependence of the action of pheromones results in some cases in which mating disruption cannot control the pest population. Similarly, aggregation of the pest population decreases the efficiency of the method unless the pheromone action is density independent. Delayed mating of females makes control easier, and may constitute one mechanism for mating disruption.     

Combining pheromone-baited and food-baited traps for insect pest control: Effects of developmental period

Summary An age-structured population dynamics model is presented that incorporates pheromone-trapping and food-trapping as control methods for an insect pest. The model yields the following results. Low rates of pest survivorship allow lower trapping rates for control. Species with long developmental periods are easier to control than those with shorter developmental periods (other factors being equal) due to lower net survival. The rates of pheromone trapping alone for effective control are usually very high. The combination of pheromone and food trapping allows control with much lower trapping rates than either method alone. Even small amounts of immigration of adult pests into the control area renders pheromone control ineffective, whereas food traps suppress both the immigrants and the resident population. Food- (or odor-) baited traps which attract both males and females are only somewhat more efficient than those which attract females alone. The existence of density-dependent population regulation assists the control program substantially, but this assistance declines as food trapping becomes a more important part of the control program. Larval competition strongly affects the required trapping rates for eradication; species in which all larvae exert strong competition are much easier to control than those in whic the younger larvae contribute little to the total competitive depression.     

Combining pheromone-baited and food-baited traps for insect pest control: Effects of additional control by parasitoids

Summary Two age-structured population dynamic models are analyzed in which pheromone-baited trapping and food-baited trapping are used simultaneously to eradicate an insect pest. The pest species is assumed to be under partial control by a host-specific parasitoid species. The two models assume that density-dependent population regulation is accomplished either by host larval competition or by means of oviposition interference among the parasitoids. The two trap types interact in a positive synergistic manner and this combination appears to be very promising as a useful combination of pest control methods. Several features of the system are examined; the feature which appears to cause the greatest problem is the possibility of the parasitoids being attracted to the pheromone or the food traps. In either case, the degree of attraction does not have to be very great to undermine the control effort. It is seen that food trapping becomes indispensible if host pheromone is used by the parasitoids as a host-locating kairomone. If odor in the food traps is used by the parasitoids as kairomone, then the situation appears more optimistic, as the reduction in efficiency of the food traps appears much less than with the pheromone traps when pheromone acts as kairomone.     

Verifying zero-infestation in pest control: A simple sequential test based on the succession of zero-samples

Summary A simple sequential test based on the succession of ‘zero's or uninfested sampling units is proposed for use in verifying zero-infestation in pest control surveys. The method is applicable efficiently to both finite and infinite populations. Problems concerning its efficiency on application are discussed.     

A measure of sexual selection for interspecific comparisons of species with diversified mating systems and different mortality schedules

Summary Based on variances in components of lifetime reproductive success (LRS), a new index of the intensity of sexual selection was proposed mainly useful for interspecific comparisons. The index was defined as the male to female ratio of the standardized variance in mating efficiency during mating period. The index can to a large extent exclude the effect from natural selection which commonly act on both sexes in mating period and also from mortality in pre-reproductive period. This empirical measure has some defects in the strict sense (i.e., dichotomy of natural and sexual selection), however, it enables interspecific comparisons of the intensity of sexual selection among different taxonomic groups of animals with various mating systems and mortality schedules.     

On the estimation of female births missing due to prenatal sex selection

This research note is prompted by a paper by Kashyap (Is prenatal sex selection associated with lower female child mortality? Population Studies 73(1): 57–78). Kashyap’s paper, which provides 40 original estimates of missing female births, relies on an alternative definition of missing female births, leading to estimates of about half the magnitude of other estimates. There appears, therefore, a real need to take stock of the concept of missing female births widely used by statisticians around the world for assessing the demographic consequences of prenatal sex selection. This research note starts with a brief review of the history of the concept and the difference between Amartya Sen’s original method and the alternative method found elsewhere to compute missing female births. We then put forward three different arguments (deterministic and probabilistic approaches, and consistency analysis) in support of the original computation procedure based on the number of observed male births and the expected sex ratio at birth.     

Mixed-Mode Oscillations Due to a Singular Hopf Bifurcation in a Forest Pest Model

In a forest pest model, young trees are distinguished from old trees. The pest feeds on old trees. The pest grows on a fast scale, the young trees on an intermediate scale, and the old trees on a slow scale. A combination of a singular Hopf bifurcation and a “weak return” mechanism, characterized by a small change in one of the variables, determines the features of the mixed-mode oscillations. Period-doubling and saddle-node bifurcations lead to closed families (called isolas) of periodic solutions in a bifurcation corresponding to a singular Hopf bifurcation.     

愚昧还是文明,哪一个离我们更近-中国人口素质逆淘汰的实证分析

中国的人口素质逆淘汰问题不仅是多学科的研究对象,而且是学术界争论的焦点。本文从城乡不同的生育率是造成人口素质逆淘汰的原因出发,采取定性分析和定量分析相结合的方法,指出静态社会中的确存在人口素质逆淘汰,但城镇化不仅控制了人口数量,而且提高了人口素质,因此,加大高等教育的投入和改善医疗卫生条件等提高我国人口素质的根本途径应和推进城镇化相结合,才能达到事半功倍的效果。     

我国男性的婚姻溢酬——基于内生选择性模型的分析

本文利用2008年的RUMiC（中印农民工调查数据）构造内生选择模型分析我国男性的婚姻溢酬。OI．S结果显示,控制个人特征和单位特征后,已婚男性的工资大于未婚男性的工资,婚姻溢酬为O．360。控制了婚姻选择性和妻子工作时间内生性后,使用Hekman两步法对此分析后发现婚姻溢酬更大一些,达到了O．523;这表明我国男性的婚姻溢酬不能简单归因于选择性假说,即已婚男性比未婚男性拥有更高的不可观测的生产力。进一步的研究发现,我国男性的婚姻溢酬可以用生产力假说中的家庭内部分工理论来解释,OLS和Heckman两步法的回归结果均表明,我国男性的婚姻溢酬随妻子的工作时间上升而下降。     

The ideology of population control in the UN draft plan for Cairo

This paper examines the influence of population control ideology on the draft plan for the UN Cairo Conference on Population and Development. It is argued that this draft plan can only be fully understood in the context of the recent history of the population control movement and of the empirical reality of population control in particular countries. The paper focuses on the origins of the ideology of population control in the eugenics movement initially, and more recently in organisations such as International Planned Parenthood Federation. The role of the United Nations Population Fund (UNFPA), in promoting an incremental approach towards the wider acceptance of population control since the first intergovernmental conference on population in Bucharest in 1974, is outlined. Despite the serious loss of credibility for the UN, through the association of the UNFPA with the Chinese population control programme — the most coercive programme of its type in history — the UN in the draft plan for Cairo continues to promote the ideology of population control. This paper argues for the need to develop a more positive model of development, which acknowledges the complementarity between the lack of development of poorer countries and their potential for significant progress, and the overdevelopment of industrialised regions, whose future growth is increasingly based on intense competition for shrinking markets.This article is based on a paper, presented to the International Geographical Union Congress at Prague, 21–27 August 1994.     

Spatio-temporal variation of natural and sexual selection in breeding populations of the coreid bug,Colpula lativentris (Heteroptera: Coreidae)

Spatio-temporal variations of lifetime reproductive succes (LRS) of both male and female individuals of a coreid bugColpula lativentris were measured and analyzed using the multiple regression method of Arnold and Wade (1984a, b). The standardized variance of LRS was larger in males than that in females as males often to secure mates for a long period whereas females could easily find mates and oviposit simply dependent on ovarial maturation. LRS was partitioned into 4 consecutive fitness components: (1) reproductive lifespan, (2) copulating efficiency, (3) guarding efficiency (for males) or oviposition efficiency (for females), and (4) number of eggs per clutch. In males copulating efficiency was the largest determining factor of LRS, whereas in females reproductive lifespan was the most important factor. Such tendencies were stable on both a yearly and local basis. Patterns of relative contribution of natural selection (reproductive lifespan and number of eggs per clutch) and sexual selection (copulating efficiency and guarding or oviposition efficiency) to LRS were clearly different between males and females. This sexual difference is, at least to some extent, thought to be brought about by sexual selection among males for mating opportunity, though no physical fight was observed among males. Directional selection on body length was found only in relation to the clutch size of females because large females tended to lay larger clutches. No significant directional selection was found in other fitness components.     

Combination of a structured aerobic and resistance exercise improves glycaemic control in pregnant women diagnosed with gestational diabetes mellitus. A randomised controlled trial

Problem

Gestational diabetes mellitus, defined as any carbohydrate intolerance first diagnosed during pregnancy, is associated with a variety of adverse outcomes, both for the mother and her child.

The claim that China's fertility restrictions contributed to the use of prenatal sex selection: A sceptical reappraisal

Most observers assume that China's fertility restrictions contribute to the use of prenatal sex selection. I question the logic and evidence underlying that assumption. Experts often stress that China's low fertility is largely voluntary, and that fertility restrictions are an unneeded safety valve. Others claim that China's ‘1.5-child’ loophole, common throughout rural areas, reinforces son preference or intensifies prenatal sex discrimination by hardening fertility constraints. These claims defy logic upon closer examination. Moreover, almost two-thirds of the exceptional distortion of the sex ratio in 1.5-child areas results from excess underreporting of daughters and enforced sex-specific stopping. Prenatal sex selection may explain the remaining third but probably reflects the stronger rural son preference that led to the 1.5-child loophole itself. The recent surge in sex selection of first births that has perpetuated the distortions also seems unrelated to policy. Some son-preferring parents who formerly wanted two children may now genuinely want only one.     

流动人口的择偶模式及其影响因素——以厦门市流动人口为例

利用“厦门市流动人口婚姻家庭抽样调查”的数据,描述流动人口择偶模式的主要特征,对流入厦门的流动人口的择偶意愿、目的、时间、标准以及途径等进行多元回归分析,在此基础上提出优化流动人口择偶模式的对策建议。分析结果表明,流动人口在对择偶模式的选择和实践上越来越重视自身的需要和体验;在各种假想的影响因素中,教育、性别和年龄的作用最大,流出的时间和收入水平的影响却相对比较微弱。     

General growth balance method: A reformulation for populations open to migration

This paper proposes a reformulation of the general growth balance method for estimating census and registration completeness so as to make it applicable even to populations that are affected by migration. It also discusses a new procedure of line fitting that could be useful in countries where the input data are severely affected by age misreporting. The method is applicable to countries where data on age distribution of the population are available for two points in time from either censuses or surveys. Following closely the original proposal of Brass, it involves adjusting the ‘partial’ birth rates for age-specific disturbances from growth and migration rates. Beyond correcting the death rates, the method is useful in inferring the relative completeness of the censuses, and in deriving a robust estimate of birth rate under certain conditions. The application of the method is illustrated using the example of the male population of the Indian state of Uttar Pradesh for the period 1981 to 1991.     

进城还是回村？——跨省婚迁者的空间选择

在经济社会转型、人口频繁流动的条件下,婚迁由乡到城的单向迁移转变成为城乡互动的双向流动。婚迁者留在城市还是回到乡村,要取决于多种条件。本研究通过测度跨省婚迁的性别比发现,自1990年来的20年间我国省际婚迁性别比下降近一半。全国省际婚迁性别比呈现城市-城镇-乡村两端大中间小的“微笑曲线”。在婚迁的空间选择上,男性以城市为主,女性则以乡村为主。进一步分析影响婚姻迁移的因素发现,经济变量中人均GDP对总婚迁和城市婚迁呈正向影响,城镇和乡村呈负向影响;居民收入和消费状况对婚姻迁移产生正向影响,但消费的城乡差别则对其产生负向影响;人口的城乡流动与迁移以及社会变量中各因素对跨省婚迁产生正向影响,而文化变量中的各因素则形成负向影响。     

Analysis of changes of insect-plant ratio-improvement of key-factor analysis for evaluating bottom-up effects in insect population dynamics

A revised key-factor analysis was presented for analyzing the temporal changes in the ratio of insect absolute number to plant resource. Ten data sets for 5 insect species were then analyzed. In this key-factor analysis, the key factor is defined as the factor contributing highly to between-year variation inR _r , the log rate of the inter-year change of the insect-plant ratio. The yearly change of plant resource was handled as a separate factor, expressed byr _pl , log ratio of plant resource in yearn to plant resource in yearn+1. The following was revealed: 1) In 7 of the 10 data sets examined,r _pl influenced variations ofR _r ; in particular in 3 casesr _pl was the main key factor. 2) Generation-to-generation fluctuations of absolute insect densities showed density dependence in 4 cases, while those of insect-plant ratios, in 8 cases. 3) The Royama model or a linear model, explained well the relationship between log insect-plant ratio (X _r ) andR _r and the relationship betweenX _r and log yearly change rate of absolute insect density (R _abs ). However, in the 7 cases in whichr _pl was a critical factor for variations ofR _r , with, increase ofX _r ,R _r showed a steeper, decrease around the equilibrium point (the point for whichR _r is 0) thanR _abs . This occurred becauser _pl tended to be negatively correlated withX _r . Consequently, in two casesX _r fluctuated cyclicly or chaotically although without the changes in plant resource, fluctuations ofX _r would be damped oscillations approaching equilibrium.     

Genetic changes of life history and behavioral traits during mass-rearing in the melon Fly,Bactrocera cucurbitae (Diptera: Tephritidae)

Quantitative genetic studies for life history and behavioral traits are important in quality control for insect mass-rearing programs. Firstly, a brief history of quality control in mass-reared insects is described. Next, the differentiation of many traits of wild and mass-reared melon flies,Bactrocera cucurbitae, in Okinawa is reviewed, and the factors which have caused variation in these traits are considered. As artificial selection pressures are thought to be more important than inbreeding depression and genetic drift in the mass-reared strain of the Okinawan melon fly, two artificial selection experiments were conducted to evaluate genetic variations and genetic correlations among life history and behavioral traits. These are divergent selections for age at reproduction and for developmental period. The genetic relationship among 5 traits, i.e. longevity, age at reproduction, developmental period, circadian period, and time of mating was clarified and discussed in relation to genetic changes of traits during the mass-rearing. The results suggest that the genetic trade-off relationships between traits should be taken into account in mass-rearing programs.