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PubMed2000

Statistical inference on associated fertility life table parameters using jackknife technique: computational aspects.

Knowledge of population growth potential is crucial for studying population dynamics and for establishing management tactics for pest control. Estimation of population growth can be achieved with fertility life tables because they synthesize data on reproduction and mortality of a population. The five main parameters associated with a fertility life table are as follows: (1) the net reproductive rate (Ro), (2) the intrinsic rate of increase (rm), 3) the mean generation time (T), (4) the doubling time (Dt), and (5) the finite rate of increase (lambda). Jackknife and bootstrap techniques are used to calculate the variance of the rm estimate, which can be extended to the other parameters of life tables. Those methods are computer-intensive, their application requires the development of efficient algorithms, and their implementation is based on a programming language that encompasses quickness and reliability. The objectives of this article are to discuss statistical and computational aspects related to estimation of life table parameters and to present a SAS program that uses jackknife to estimate parameters for fertility life tables. The SAS program presented here allows the calculation of confidence intervals for all estimated parameters, as well as provides one-sided and two-sided t-tests to perform pairwise or multiple comparison between groups, with their respective P values.

Animals↗
PubMed2000

Influence of sublethal exposure to abamectin on the biological performance of Neoseiulus longispinosus (Acari: Phytoseiidae).

Effects of sublethal exposure to abamectin on the biological performance of Neoseiulus longispinosus (Evans) were studied under ambient laboratory conditions of 28 +/- 2 degrees C and 80 +/- 15% RH with 24 h light. The red form of the twospotted spider mite, Tetranychus urticae Koch, complex (Acari: Tetranychidae), was offered as prey. The LC50 obtained from the contact bioassay at 48 h after treatment was 0.015 ppm (AI). A big change in kill for a given variation in dosage for the regression slope probably indicated that abamectin was unlikely selective. Sublethal exposure to abamectin caused a reduction in survival with the female reaching 50% mortality by the sixth day and the male 4 d later. The mean preoviposition period was extended by almost 1 d, whereas the mean oviposition period was shortened by almost 5 d causing a reduction in the mean fecundity female-1 to almost half that of the untreated females. The net reproductive rate (Ro), the intrinsic rate of increase (rm), and the finite rate of increase (lambda) of the treated females were markedly inferior. Treated males were seriously affected; the mean life span was almost half that of the untreated.

Animals↗
PubMed2000

Temperature dependent development of the parasitoid Colpoclypeus florus (Hymenoptera: Eulophidae) in the laboratory.

Development, fecundity, and longevity of Colpoclypeus florus (Walker), a parasitoid of Adoxophyes orana (Fischer von Röslerstamm) (Lepidoptera: Tortricidae), were studied under laboratory conditions at different constant temperatures. Developmental time from egg to adult was inversely related to temperature and at 25 degrees C was 12.81 +/- 0.19 d. No adults emerged at 30 degrees C. The thermal units required for development from egg to adult were 232.56 +/- 19.5 degree-days. Female C. florus oviposited (mean +/- SEM) on average 30.7, 57.4, 46.6, and 34.1 eggs at 15, 17, 20, and 25 degrees C. respectively. Adult longevity was 11 +/- 1.25 d at 17, whereas it decreased to 4.5 +/- 0.4 at 25 degrees C. Honey significantly increased longevity for both males and females. The highest net reproductive rate was 30.739 at 17 degrees C, whereas the highest intrinsic rate of increase and the shortest doubling time occurred at 25 degrees C.

Animals↗
PubMed2001

The presence of chemicals exuded by fish affects the life-history response of Ceriodaphnia cf. dubia to chemicals with different mechanisms of action.

The toxicity of chemicals with different mechanisms of action (3,4-dichloroaniline, fenoxycarb, and chlorpyrifos) to the cladoceran Ceriodaphnia cf. dubia was examined in the presence and absence of chemicals exuded by fish, termed fish kairomones. A range of life-history traits were examined, including mean brood sizes, survival, net reproductive rate (Ro) and population growth rate (r). Cladocerans exposed to 3,4-dichloroaniline showed similar sensitivities in the presence and absence of fish kairomones with respect to all of the life-history traits examined. The presence of fish kairomones reduced the sensitivity of cladocerans to fenoxycarb with respect to mean brood sizes and r but increased their sensitivity in terms of Ro. The presence of fish kairomones increased the sensitivity of cladocerans to chlorpyrifos with respect to survival, r, Ro, and mean brood sizes. The general trends observed were similar to those shown when C. cf. dubia was exposed to these chemicals under low food conditions, and it is suggested that the effects of fish kairomones on toxicity may be attributed to the reduction in feeding rates observed when C. cf. dubia is exposed to fish kairomones.

Aniline Compounds↗
PubMed1991

Epidemio-entomological survey of Japanese encephalitis in Korea.

In order to determine the seasonal prevalence and population dynamics of Culex tritaeniorhynchus in relation to the epidemics of Japanese encephalitis, and ecology of these vector mosquito in Kyungpook Province, Korea, studies were conducted during the period of 7 years from 1984 to 1990. Cx. tritaeniorhynchus first collected in June between 4th and 28th, and trapped in large numbers during the period from mid-August to early September, showed a simple sharply pointed one-peaked curve. There was a gradual decrease from mid-September, with a very small number of them collected until early October in every year. The average number of Cx. tritaeniorhynchus rapidly decreased after 1985, and the number became particularly low in 1989. The highest population density, which was observed in August during the initial three years, was found to be delayed in the following years, accompanied by a decrease in the number of mosquitoes. In the trend of nocturnal activity of Cx. tritaeniorhynchus, with oncoming darkness they become very active, gradually decreasing in activity toward mid night, but slightly increasing toward dawn. The immature stages of Cx. tritaeniorhynchus were first found in rice fields contributing to peak adult densities in mid-July. The highest average densities of Cx. tritaeniorhynchus was 14,900 per m2 on mid-August 19th. The larval Cx. tritaeniorhynchus showed high resistance levels and resistance ratios against 5 organophosphorus compounds. In the adult horizontal life table characteristics of Kyungsan colonies of Cx. tritaeniorhynchus under insectary conditions, life expectancy was 28.3 days for males and 59.8 days for females. The net reproductive rate was 7.8 and generation time was 25.6 days.

Animals↗
PubMedDate not supplied

Knowledge and attitudes of rural adolescent girls regarding reproductive health issues.

BACKGROUND: Adolescent girls (10-19 years old) comprise about 22% of women in India. They are the mothers of tomorrow and the burden of planned reproduction rests on them. Yet very little is known about their knowledge and attitudes towards reproductive health issues--a crucial aspect if India is to achieve the net reproduction rate of 1 by AD 2016. This study aimed to gather information on areas required for the planning of family life education strategies. METHODS: This cross-sectional study was conducted in the government schools and anganwadi premises of three villages of the primary health centre, Chhainsa, under the Comprehensive Rural Health Services Project Area (CRHSP), Ballabgarh, Haryana. The participants were 254 girls aged 13 to 17 years, who had attained menarche. A pre-tested interview schedule was administered to each girl after taking permission from the principals and parents and with the consent of the participants. The knowledge and attitudes regarding age at marriage, concept of small family norm, family size and preference for a son were assessed. RESULTS: All the girls were aware that there is a law regarding legal age of marriage but only 165 (65%) of them knew the correct legal age. Early marriage was preferred by 19 (7.6%). Though 214 (84.3%) girls were aware of the small family norm, only 19 (8.8%) knew the exact norm. A preferred family size of two or less was reported by 151 (59.2%). Preference for a son was reported by 233 (91.7%). CONCLUSION: All the girls were aware of the small family norm, but few could correctly define it. Though most girls preferred a two-child family, almost all of them had a preference for at least one son. This preference for a son could dominate their future decision-making. As attitude development is a long-term process, there is indeed a long way to go.

Adolescent↗
PubMed1987

Effect of declining fertility on population aging in India: an application of Coale's analytical model.

This paper attempts to gauge the effect of constantly declining fertility on population aging in India through the application of an analytical model proposed by Ansley Coale (1972), which employs stable population theory. The author has assumed a linearly constant fertility decline in India to obtain a net reproduction rate equals 1 by the year 2001. The projected age distribution in 2001 shows that the proportions of males and females aged 65+ will be 3.66% and 3.98% respectively. This means that there would be an increase of 7.3% in the proportion of males (65+) from 1971 to 2001. The corresponding increase for females is more, 17.4%. The median age of males increases from 16.59 to 22.92 years during the same period. For females, the increase is from 16.64 to 22.75 years. Although the proportional increase of the aged is not very substantial, the absolute magnitude it implies is very large. It has far reaching implications in the development process in India.

Adult↗
PubMed1982

Long-range global population projections, as assessed in 1980.

UN medium range projections prepared in the 1980 assessment projected the population of individual countries up to the year 2025. The long range projections discussed here were prepared by projecting the population of 8 major world regions from 2025-2100. The purpose of the projection was to observe the implications of the changes from the 1978 assessment made in the 1980 medium range projections on the long range projections of the world's populations. As in previous projections, high, medium, and low variants were prepared in which fertility is assumed to be constant at the replacement level but at different times in the future. In addition, these projections contain 2 variants not previously prepared--namely, the growth and decline variants, in which the ultimate net reproduction rate is 1.05 and 0.95, respectively. In all the variants, expectation of life at birth is assumed to reach 75 years for males and 80 for females. According to the current medium variant projection, the earth's population will become stationary after 2095 at 10.2 billion persons, compared with a total of 10.5 billion projected in the 1978 assessment. The lower projection is largely attributable to a recent decline in the growth rate of several countries in South Asia which was greater than previously assumed. When the world population becomes stationary, both crude birth and death rates would be about 13/1000. In the decline variant, total population would peak at 7.7 billion in 2055, then decline gradually to 7.2 billion in 2100. The total population as projected by the growth variant would equal 14.9 billion in 2100 and would still be growing slowly. Between 1980 and 2050, 95% of the world's growth will occur in the currently less developed regions. Their share of total population will increase from 75-85% during that period. The age structure in all regions is expected to converge to 1 in which the median age is 39 years, the proportion both below age 15 and above age 64 is about 19% each, and the dependency ratio is about 60. A precise degree of accuracy cannot be specified, but the argument is made that the actual future population of the world is very likely to fall within the range of the projection variants and probably not far from the medium variant.

Africa↗
PubMed1986

[Age, parity, and time in fertility].

The authors analyze fertility trends in Japan from 1935 to 1969 using "vital statistics data upon which age-parity adjusted net reproduction tables were constructed for 35 different female birth cohorts." These tables are used to calculate "cohort net reproduction rate and total fertility rate by parity and age, [as well as] mean age at first birth, second birth, etc. and average length of birth interval in each cohort." (summary in ENG)

Age Factors↗
PubMed1991

Momentum and the growth-free segment of a population.

In the scenario of a sudden drop in fertility to replacement level. Preston (1986) argued that the population segment under age T, the length of generation, remained growth-free. Here we first present a new relationship for the momentum of any observed population as the ratio of 1) the proportion of the observed population under the mean age at childbearing to 2) the proportion of its life table population under that mean age. We then use that relationship to demonstrate Preston's approximation. Growth factors for other population segments are also presented. When the initial population is stable, momentum can be approximated as a function of the net reproduction rate alone.

Age Factors↗
PubMed1987

Studies on autogeny in Culex tarsalis: 3. Life table attributes of autogenous and anautogenous strains under laboratory conditions.

The reproductive biology and life table attributes of autogenous and anautogenous strains of Cx. tarsalis which were selected from the same parent colony were compared under laboratory conditions. Autogenous mosquitoes required 1 day longer to complete immature development, but oviposited 1 to 2 days earlier than anautogenous mosquitoes. Autogenous females readily imbibed blood meals from restrained chickens if ovarian maturation had not progressed to Christophers' Stage III. Wing length and life expectancy were not significantly different between strains; however, autogenous females laid a significantly smaller number of eggs per raft during initial oviposition than anautogenous females. Egg raft size did not differ significantly between strains during subsequent ovipositions resulting in similar net reproductive rates (Ro). Earlier oviposition and a comparable Ro resulted in a greater intrinsic rate of increase (rm) and birth rate (b) for autogenous than anautogenous cohorts. Thus, highly autogenous populations would be able to exploit newly created surface water breeding sources more rapidly than highly anautogenous populations. However, highly autogenous populations probably would not be able to transmit a horizontally maintained arbovirus as efficiently as anautogenous populations, since autogenous females imbibe their initial blood meal later in life than anautogenous females.

Actuarial Analysis↗
PubMed1982

Immigration and the stable population model.

This paper reports on work aimed at extending stable population theory to include immigration. its central findings is that, as long as fertility is below replacement, a constant number and age distribution of immigrants (with fixed fertility and mortality schedules) lead to a stationary population. Neither the level of the net reproduction rate nor the size of the annual immigration affects this conclusion; a stationary population eventually emerges. How this stationary population is created is studied, as is the generational distribution of the constant annual stream of births and of the total population. It is also shown that immigrants and their early descendants may have fertility well above replacement (as long as later generations adopt and maintain fertility below replacement), and the outcome will still be a long-run stationary population.

Adolescent↗
PubMed1980

Laboratory colonization and life table statistics for geographic strains of Simulium decorum (Diptera: Simuliidae).

Colonization techniques were developed in order to select mating strains from four geographic populations of Simulium decorum. Although mating strains were established from each locale, emphasis was shifted toward developing permanent colonies from Dryden Lake, New York, USA and Warm Springs, Georgia, USA. The net reproductive rate (Ro) was computed for the parental, F1, and F2 generations of each strain in order to assess the effects of colonization through successive generations. Ro increased rapidly for both strains from parental (range of 0.34-3.5) through F2 generations (range of 16.2-21.6). Analysis of Ro components indicated that the increases in Ro were the result of two parameters that reflect the propensity of flies to mate in confinement, suggesting that selection for mating is rapid. Multiple regression analysis indicated no significant differences between strains or generations when tested against fecundity (range of 391-519) and survival of immatures (range of 90.3-97.2%). A slight positive correlation (regression coefficient of 0.0016, P less than .01) was observed between larval density (range of 284-4,439 larvae per rearing) and survival of immatures, suggesting that the limits of the rearing system with regard to crowding were not approached. Both strains readily adapt to the laboratory and are currently in the fifth generation.

Animals↗
PubMed1997

Effect of Eucalyptus feeding in the development, survival and reproduction of Tynacantha marginata (Heteroptera: Pentatomidae).

The effect of feeding on Eucalyptus leaves of Tynacantha marginata (Heteroptera: Pentatomidae) was studied in Brazil. The use of this plant as a complementary food source for the predatory bug increased its oviposition period, generation time, and net reproductive rate. Eucalyptus leaves apparently had no influence on the survival and development of T. marginata.

Animals↗
PubMed1997

Life-table attributes of Anopheles albimanus (Wiedemann) under controlled laboratory conditions.

The life-table attributes of a laboratory-colonized strain of Anopheles albimanus Wiedemann from El Salvador were investigated under controlled environmental conditions (26 +/- 2 degrees C, 60 +/- 2% RH, and 16:8 L:D photoperiod). Larvae pupated seven days after eclosion and the adults emerged on day eight. Adult emergence success was 91% and sex ratio was not significantly different from 1:1. Females took a blood meal one day after emergence and laid eggs two days later. The mean time of reproduction was 10.8 days and the expectation of life at emergence was 18.8 and 14.1 days for females and males, respectively. The daily survivorship of females at emergence was 0.97, and their net reproductive rate, age at mean cohort reproduction, instantaneous rate of increase, and mean generation time was 309.2, 10.8 days, 0.319, and 18 days, respectively. The life expectancy of females 10 days after emergence was 13.4 days, and they were capable of taking four to six additional blood meals.

Animals↗
PubMed1997

[Life tables of Blattella germanica (Dictyoptera: Blattellidae) under laboratory conditions and their importance for its control].

A study of the life tables of Blatella germanica (L.) 1767 was conducted under laboratory conditions. 3 treatments were used a according to the number of individuals in each breeding flask (A = 9 flasks with 20-25 individuals, B = 17 flasks with 30-35 individuals, and C = 30 flasks with a newly hatched nymph each). The main parameters of the population growth were calculated by the TABVID software . The respective values for treatments A and B were the following: net reproduction rate (Ro 2.23 and 2.37), natural increase finite rate (lambda = 1.06), natural increase intrinsic rate (r = 0.06), and mean generational time (T = 13.89 and 15.64). The behaviour of the survival probability by age, the fertility rate, and the mortality rate were graphically registered. Life expectancy for treatment C was 16.47 and the survival rate for this treatment was represented by a graph. Graphics of the growth curve of this species and of the survival rate for treatments A and B were shown. The latter was concave, which means that mortality is higher during the young stages. This study provides esential cuantitative basic date that allow to carry out a more efficient control if fight is directed to the period where the highest natural mortality was found, that is, at the step from nymph 6 to adult in treatments A and B.

Animals↗