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PubMed2006

Life tables of Venturia canescens (Hymenoptera: Ichneumonidae) parasitizing the Mediterranean flour moth (Lepidoptera: Pyralidae).

Effects of temperature, adult feeding, and host instar on life table parameters of Venturia canescens Gravenhorst (Hymenoptera: Ichneumonidae) parasitizing larvae of Ephestia kuehniella Zeller (Lepidoptera: Pyralidae) were studied in the laboratory. Experimental adults lived under various regimes of temperature (15, 20, 25, and 30 degrees C), food supply (with or without access to honey), and host instar (second, third, fourth, and fifth). Temperature increase resulted in higher values of the intrinsic rate of natural increase (r(m)), the net reproductive rate (R(o)), the finite capacity of increase (lambda), and the gross reproductive rate (GRR), whereas it was followed by decrease of the mean generation time (G) and the doubling time (DT) values. Feeding on honey caused remarkable increase of r(m), R(o), and GRR, whereas r(m) and lambda reached their maximum when full-grown hosts (fifth instar) were parasitized. This is the first time life table parameters of V. canescens have been studied. The findings of the current study are discussed on the basis of improving V. canescens performance as a biological agent against moth pests of stored products.

Animals↗
PubMed1977

Fertility and family planning in Hungary.

Hungary's birth rate has been declining fairly steadily since World War II, and Hungarian population policy is aimed at increasing fertility to at least replacement level through social, health, and economic benefits to encourage childbearing. Figures for the mid-1970s indicate that birth rates have been rising. Whether these recorded increases may be permanent is examined through analyses of data on Hungarian fertility since 1900 and through retrospective and prospective surveys of family planning attitudes and practice. Both fertility statistics and surveys of family-size desires document a trend toward the two-child family and a birth rate too low to achieve the desired net reproduction rate of more than one. The surveys also show that family planning has become more prevalent in recent decades, and previously heavy reliance on abortion and traditional contraception is increasingly giving way to use of modern contraceptives.

Abortion, Induced↗
PubMed1994

Age composition, natural survival and population growth of Anopheles fluviatilis James, 1902, the major malaria vector in the endemic belt of Koraput District, Orissa, India.

The population growth of Anopheles fluviatilis, the major malaria vector, was studied in the hill tracts of Koraput district. Immature duration ranged from 11 to 14 days (mean = 12.42 +/- 0.99) in rainy and 12 to 17 days (mean = 14.78 +/- 1.64) in cold season. The probability of immature survival through different developmental stages was maximal in ponds. Daily survival rate of adults fluctuated between 0.55 and 0.92. The net reproductive rate (Ro) was estimated to be 3.0200 for cold and 0.6486 for rainy season. The mean generation time (T) was slightly longer in cold season (22.32 days) than rainy season (21.24 days). The intrinsic rate of population increase (rm) and consequently the finite rate of increase (lambda) were estimated for cold and rainy seasons. Population growth based on adult resting density was also assessed for different seasons.

Age Distribution↗
PubMed1992

Temperature influence on life table statistics of the chicken mite Dermanyssus gallinae (Acari: Dermanyssidae).

An age-specific life table for the chicken mite Dermanyssus gallinae (DeGeer, 1778) was based on various observations carried out at 25 degrees C. The generation time was calculated to be 16.8 days; the intrinsic rate of natural increase was 0.12 per day, and the net reproductive rate was 7.2. A nonlinear function was found satisfactory to describe the developmental rate of the different immature life-stages at temperatures below 40 degrees C. The stage-specific survival of the immature life-stages was generally high between 10 and 37 degrees C, but decreased quickly outside this temperature range. Most of the eggs were laid during the first three weeks of the adult life. The proportion of surviving females rapidly decreases after moulting to the adult stage. At a temperature of 30 degrees C, the highest number of eggs (3 eggs per day) was laid.

Animals↗
PubMed2006

Fertility and abortion rates in the United States, 1960-2002.

This paper provides a general overview of trends in the United States (US) birth, fertility and abortion data from 1960 to 2002. Rates by age, race and Hispanic origin are also discussed. Data presented in this paper are derived primarily from published reports of the US government's Centers for Disease Control and Prevention's National Center for Health Statistics. In 2002, there were 4,021,726 births in the US. The general fertility rate was 64.8 births per 1,000 women aged 15-44 years, the total fertility rate was 2013.0 children per 1,000 women, and the net reproduction rate was 968 daughters per 1000 women. These rates have declined in the US since 1960, down by at least 44% for all rates. While these rates have been declining, there are substantial differences in fertility patterns by age and race and Hispanic origin. Rates for women, 30 years of age and over, increased between 1980 and 2002. In contrast, rates for women under 25 years of age rose considerably during the late 1980s, and then decreased sharply since 1991. Rates for women in their late twenties (25-29 years of age), the principal childbearing ages, have fluctuated within a narrow range throughout this period (1980-2002). As a result of the increase in births to older women, the mean age of mother at first birth increased by nearly 4 years from 1968 to 2002. In 2000, the latest year for which data are available, there were 21.3 induced abortions per 1000 women aged 15-44 years, down from 27.4 in 1990. The total abortion rate, average number of legally induced abortions that would occur to a hypothetical cohort of 1000 women, was 672.0 abortions per 1,000 women in 2000, down from 785.5 in 1980. The abortion rate has declined fairly steadily since 1980. Like the birth and fertility rates, substantial differences in abortion rates exist by age and race and Hispanic origin. The rates of induced abortion increased for women in their thirties between 1980 and 2000, whereas rates for women under 25 years of age and women 40 years of age and over decreased since 1980. The rate for women 25-29 years of age changed little. The rate of induced abortion was considerably higher for non-Hispanic black women (57.4) in 2000 than for non-Hispanic white women (11.7). The rate for Hispanic women (30.6) was intermediate. The total abortion rate was also much higher for non-Hispanic black women than non-Hispanic white and Hispanic women.

Abortion, Induced↗
PubMed2006

Temperature-dependent development and population growth of Tetraneura nigriabdominalis (Homoptera: Pemphigidae) on three host plants.

The root aphid Tetraneura nigriabdominalis (Sasaki) (Homoptera: Pemphigidae) is a pest of many Gramineae species; however, little is known about its biology and relationships with host plants. The objectives of this study were to quantify the effects of temperature on development, longevity, fecundity, and population growth of T. nigriabdominalis and to assess the effects of host plant on development of T. nigriabdominalis. The effects of temperature on performance of this root aphid were determined at 10, 15, 20, 25, 30, and 35 +/- 1 degrees C on rice roots, Oryza sativa L. Nymphal stages from birth to adult decreased from 46.3 d at 10 degrees C to 8.5 d at 30 degrees C. Aphid survival and development were lowest at 35 degrees C, and no aphid produced progeny at this temperature. Average adult longevity decreased from 23.3 d at 15 degrees C to 8.2 d at temperatures up to 35 degrees C. Average number of nymphs produced per female was highest at 25 degrees C; averaging near 30 nymphs per female, but it dropped to near zero at both 10 and 35 degrees C. The highest intrinsic rate of increase (r(m)) was 0.241 at 30 degrees C. Net reproductive rate (R(0)) ranged from 29.8 at 25 degrees C to 0.2 at 10 degrees C. The generation time (GT) decreased with increasing temperatures from 60.3 d at 10 degrees C to 13.8 d at 30 degrees C. In addition, root aphids reared at 30 degrees C on three host plants [O. sativa, Zea mays L. and Sorghum bicolor (L.) Moench] revealed that the developmental time of the nymphal stages averaged 6.9 d when reared on O. sativa and 10.7 d when reared on Z. mays. Comparison of the nitrogen content of the three host plants indicated that the root nitrogen content was highest in O. sativa. The effect of nitrogen content on aphid performance, however, is still not clear. Other factors, such as plant secondary chemistry, may play a role in affecting aphid performance.

Animals↗
PubMed1995

Comparison of the life table characteristics of Anopheles sergentii (Diptera: Culicidae) from two malarious areas in Egypt.

Life table characteristics were examined for the malaria vector, An. serenti from two Faiyum villages: Tersa (T) and El Nazlah (N) from Siwa oasis (Sw) under constant laboratory conditions at 25 degrees C and 70% RH. Females of T, N and Sw completed 4, 5, and 2 gonotrophic cycles (gc) respectively. The first gc required a significantly longer period (p<0.05) than the subsequent ones. Development times for Sw immatures were longer (p<0.05) than for the other colonies. Life expectancies at emergence for males of the 3 colonies were significantly shorter than for their respective females. Generation time was shorter (p<0.05) for T (mean = 31.15 days) than for Sw (37.81 days) or N (43.64 days) colonies. The birth rate of Sw colony (mean = 0.33 female female/female) was significantly higher (p<O.05) than those of the other colonies. The other biological parameters: fecundity, egg hatch times and rates, survivorship from egg eclosion to adult emergence, male and survivorships, net reproductive rate, intrinsic rate of increase all showed no colony variations. The study concluded that variation among colonies in certain biological aspects may not reflect strain differences.

Age Factors↗
PubMed2004

Comparative studies on biomass production, life cycles and composting efficiency of Eisenia fetida (Savigny) and Lampito mauritii (Kinberg).

Comparative studies were performed to evaluate composting potential, biomass growth and biology of a non-native (Eisenia fetida) and an endemic (Lampito mauritii) species of earthworm in the semiarid environment of Jodhpur district of Rajasthan in India. Earthworms were reared in a mixed bedding material comprised of biogas slurry, cowdung, wheat straw, leaflitter, sawdust and kitchen waste. The percentage of organic carbon of the culture bedding material declined upto 105 days with E. fetida and 120 with L. mauritii. The percentage of nitrogen, phosphorous and potassium increased as a function of the vermicomposting period. In contrast, C/N and C/P ratios decreased day by day. Both species were effective for decomposition and mineralization of mixed bedding in the semiarid environment. A comparative assessment of biomass growth of E. fetida and L. mauritii was done under controlled laboratory conditions. The optimum temperature, moisture content and pH for E. fetida were 25 degrees C, 70% and 6.5, respectively. However, the optimum temperature, moisture content and pH for growth and development of L. mauritii were 30 degrees C, 60% and 7.5, respectively. The biology and reproductive rates of both species were also studied in the laboratory using mixed bedding. Cocoon production was higher for E. fetida than L. mauritii. The net reproductive rate was 9 per month in the case of E. fetida and 1 per month for L. mauritii. Fertilized eggs of E. fetida and L. mauritii developed into adults within 4 and 5 1/4 months, respectively. These observations indicate E. fetida may be a more efficient breeder than L. mauritii in the desert region of Rajasthan.

Analysis of Variance↗
PubMed1976

Influence of instantaneous fertility decline to replacement level on population growth: an alternative model.

If age-specific birth rate mx of a stable population drop abruptly to mx/Ro, where Ro is the net reproduction rate, then, according to Keyfitz, the size of the ultimate stationary population relative to that at the beginning of the process is given by I = beoo(Ro - 1)/(rmuRo), where b and r are the birth rate and the rate of growth, respectively, of the stable population, eoo the life expectancy at birth, and mu the average age at childbirth in resulting stationary population. Noting that the decline in mx need not necessarily be uniform, investigation has veen carried out to examine the effect on I when fertility decline is more rapid at higher ages. In particular, the effect of the reduced age-specific rates such as mxe-rx (which also produces a stationary population) has been analyzed, and simplifications of the results carried out separately for three different models of the net maternity function. It has also been shown the when mx drops abruptly to some m* x, where the form of m*x need not be specified except for the restriction that the resulting population will be stationary, the value of the index can be approximately obtained from I* = beoo (1 - rmu/2), where mu is the average age at childbearing of theinitial stable population.

Birth Rate↗
PubMed1991

A true rate of population growth--Lotka's intrinsic rate of natural increase revisited.

In this paper, Lotka's intrinsic rate of current population growth is evaluated. A new method of computing the net reproduction rate and a new rate of population growth are proposed. The proposed rate is the rate of growth of the female population per woman per year. The rate is positive, equal to zero, or negative as a population is increasing, remaining stationary, or decreasing. The rate for the 1987 U.S. white female population was R = -0.0037. This means that the white population was decreasing in 1987 and was losing 3.7 females for every 1000 women per year.

Female↗
PubMedDate not supplied

Colonization and laboratory maintenance of Anopheles albimanus Wiedemann in Venezuela.

Anopheles albimanus is one of the main vectors of malaria in Central America and the Caribbean, based on its importance, there are previous reports of the successful colonization of this species in Latin America countries. Mosquitoes were collected in the Aragua State of Venezuela colonized in the laboratory, using a simple and efficient maintenance method. Based on life table calculations under well established laboratory conditions, the Survival Rate Probability was constant and always close to 1 in immature stages, the Reproductive Net Rate (Ro) was 3.83, the generation time (Tc) was 24.5 days and the Intrinsic Growth Rate (rm) was 0.0558. This is the first report of the colonization of A. albimanus in Venezuela.

Animals↗
PubMed1978

The momentum of population growth with time dependent net maternity function.

The momentum of population growth problem of Keyfitz is generalized to contain a gradual change of the age-specific birth rate ro the level of bare replacement. Assuming a time dependence for the net maternity function of the form (formula: see text) R being the net reproductive rate, we show that for the Malthusian model the asymptotic birth rate is increased by exp (r/lambda), where r is the rate of increase of the population before t = 0. A numerical method for obtaining the asymptotic birth rate for a general net maternity function with the same time dependence is outlined.

Age Factors↗
PubMed1997

[Population parameters of three parasitoids (Hymenoptera: Scelionidae, Encyrtidae) hosted by the predator Podisus nigrispinus (Heteroptera: Pentatomidae)].

The reproductive parameters of Telenomus podisi, Trissolcus brochymenae (Hymenoptera: Scelionidae) and Ooencyrtus sp. (Hymenoptera: Encyrtidae) were studied for three generations on their natural host Podisus nigrispinus (Dallas, 1851) (Hemiptera: Pentatomidae). A parasitism rate of 10 eggs/day/species was used under laboratory conditions of 27 +/- 1 degrees C, 60 +/- 10% RH and 14 h of photophase. No significant differences were detected between generations in terms of net reproductive rate (Ro), intrinsic rate of natural increase (rm), generation time (T) and the effect of doubling time on population increase (DT). However, T. podisi and T. brochymenae had significantly higher Ro and rm values, and lower T and DT values, with rm 1.59 and 1.50 times higher than Ooencyrtus sp., respectively. In addition the former species also had shorter egg-adult period, greater longevity of females and reproduction period than the other species. These results confirm the greater reproductive potential of T. podisi and T. brochymenae, which are commonly found parasitizing P. nigrispinus.

Animals↗
PubMed2006

Evaluation of Vaccinium spp. for Illinoia pepperi (Hemiptera: Aphididae) performance and phenolic content.

Host acceptance and population parameters of the aphid Illinoia pepperi (MacGillivray) (Hemiptera: Aphididae) were measured on highbush blueberry, Vaccinium corymbosum L. 'Elliott', and the wild species Vaccinium boreale Hall and Aalders, Vaccinium tenellum Aiton, Vaccinium pallidum Aiton, Vaccinium hirsutum Buckley, Vaccinium myrsinites Lamarck, and Vaccinium darrowi Camp. After 24 h of exposure, significantly fewer aphids remained in contact with V. boreale and V. hirsutum compared with V. corymbosum Elliott, V. darrowi, and V. pallidum. Length of the prereproductive period of I. pepperi was significantly longer on V. boreale and V. myrsinites, in contrast to V. corymbosum. Fecundity was also lower on V. boreale, V. hirsutum, V. myrsinites, and V. darrowi. Survivorship of I. pepperi 42 d after birth was significantly lower on V. hirsutum compared with the remaining Vaccinium spp. Reduced I. pepperi performance resulted in significantly lower intrinsic rate of increase (r(m)) values being associated with V. myrsinites, V. boreale, V. hirsutum, and V. darrowi, compared with V. corymbosum. Net reproductive rate (R(o)), generation time (T), and doubling time (T(d)) of I. pepperi also were affected by the Vaccinium spp. Total phenolic and flavonol content varied between Vaccinium spp., with some high phenolic content Vaccinium spp. having reduced aphid performance. However, no significant correlation between phenolics and I. pepperi performance was detected. Results from this study identified several potential sources of aphid resistance traits in wild Vaccinium spp.

Animals↗
PubMed2001

Development, survival and reproduction of black citrus aphid, Toxoptera aurantii (Hemiptera: Aphididae), as a function of temperature.

The development, survival, and reproduction of the black citrus aphid Toxoptera aurantii (Boyer de Fonscolombe) were evaluated at ten constant temperatures (4, 7, 10, 15, 20, 25, 28, 30, 32 and 35 degrees C). Development was limited at 4 and 35 degrees C. Between 7 and 32 degrees C, developmental periods of immature stages varied from 44.2 days at 7 degrees C to 5.3 days at 28 degrees C. Overall immature development required 129.9 degree-days above 3.8 degrees C. The upper temperature thresholds of 32.3, 28.6, 29.3, 27.2, and 28.6 degrees C were determined from a non-linear biophysical model for the development of instars 1-4 and overall immature stages, respectively. Immature survivorship varied from 82.1 to 97.7% within the temperature range of 10-30 degrees C. However, immature survivorship was reduced to 26.3% at 7 degrees C and 33.1% at 32 degrees C. Mean adult longevity was the longest (44.2 days) at 15 degrees C and the shortest (6.2 days) at 32 degrees C. The predicted upper temperature limit for adult survivorship was at 32.3 degrees C. Total nymph production increased from 16.3 nymphs per female at 10 degrees C to 58.7 nymphs per female at 20 degrees C, declining to 6.1 nymphs per female at 32 degrees C. The estimation of lower and upper temperature limits for reproduction was at 8.2 and 32.5 degrees C, respectively. The population reared at 28 degrees C had the highest intrinsic rate of increase (0.394), the shortest population doubling time (1.8 days), and shortest mean generation time (9.5 days) compared with the populations reared at six other temperatures. The population reared at 20 degrees C had the highest net reproductive rate (54.6). The theoretical lower and upper temperature limits for population development, survival and reproduction were estimated at 9.4 and 30.4 degrees C, respectively. The biology of T. aurantii was also compared with three other citrus aphid species.

Animals↗
PubMed2004

Biology of three species of Agistemus (Acari: Stigmaeidae): life table parameters using eggs of Panonychus citri or pollen of Malephora crocea as food.

The biology and life table parameters of Agistemus industani Gonzalez, A. cyprius Gonzalez, and A. floridanus Gonzalez (Acari: Stigmaeidae) were studied under laboratory conditions using two food sources: Panonychus citri (McGregor) eggs or ice plant, Malephora crocea (Jacquin) Schwantes pollen at 25 degrees C. The larval, protonymph, deutonymph, and adult stages of A. industani fed on citrus red mite eggs. All active stages of A. industani, except the larva, fed on all P. citri stages and the larval stage could not feed on P. citri adults. All immature stages of A. industani fed on M. crocea pollen. Agistemus cyprius larvae fed on P. citri eggs and larvae or ice plant pollen. The nymphal stages fed on P. citri eggs, larvae, and protonymphs but not deutonymphs or adults while A. cyprius deutonymphs and adults fed on all P. citri stages. Adult and nymphal stages of A. cyprius fed on ice plant pollen and successfully completed their development while A. floridanus did not. Agistemus floridanus larvae fed only on P. citri eggs, while the other stages fed on P. citri eggs, larvae, and protonymphs. The developmental times from egg to adult for A. industani and A. cyprius when fed M. crocea pollen were 11.3 and 13.4 days, respectively. Agistemus floridanus was unable to complete its life cycle on a diet of only M. crocea pollen. Agistemus industani, A. cyprius, and A. floridanus completed development from egg to adult in 11.7, 13.8, and 10.8 days, respectively, when fed P. citri eggs. The intrinsic rate of increase (r(m)) values for A. cyprius and A. industani were 0.0311 and 0.1201 per day on the pollen diet. The net reproductive rate (Ro) was 3.58 for A. cyprius and 10.07 for A. industani with generation times (T) of 45.2 and 35.1 days, respectively, on the ice plant pollen diet. The r(m) values for A. cyprius, A. floridanus, and A. industani on the P. citri egg only diet were: 0.0562, 0.1001, and 0.1031 per day, respectively. The Ro values for each species fed P. citri eggs only were: 6.36, 7.90, and 18.70 for A. cyprius, A. floridanus, and A. industani and the generation times (T) for each of the three species were: 35.2, 29.9 and 37.8 days, respectively.

Animals↗
PubMed2005

Demographic consequences of age-structure in extreme environments: population models for arctic and alpine ptarmigan.

Organisms living in arctic and alpine environments are increasingly impacted by human activities. To evaluate the potential impacts of global change, a better understanding of the demography of organisms in extreme environments is needed. In this study, we compare the age-specific demography of willow ptarmigan (Lagopus lagopus) breeding at arctic and subalpine sites, and white-tailed ptarmigan (L. leucurus) breeding at an alpine site. Rates of egg production improved with age at the alpine and subalpine sites, but the stochastic effects of nest and brood predation led to similar rates of annual fecundity among 1-, 2-, and 3+-year-old females. All populations had short generation times (T<2.7 years) and low net reproductive rates (R0<1.2). Stable age distributions were weighted towards 1-year-old females in willow ptarmigan (>59%), and to 3+-year-old females in white-tailed ptarmigan (>47%). High damping ratios (rho>3.2) indicated that asymptotic estimates were likely to match natural age distributions. Sensitivity and elasticity values indicated that changes in juvenile survival would have the greatest impact on the finite rate of population change (lambda) in willow ptarmigan, whereas changes to the survival of 3+-year-old females would have a greater effect in white-tailed ptarmigan. High survivorship buffers white-tailed ptarmigan in alpine environments against the potential effects of climate change on annual fecundity, but may make the species more sensitive to the effects of pollutants or harvesting on adult survival. Conversely, processes that reduce annual fecundity would have a greater impact on the population viability of willow ptarmigan in arctic and subalpine environments. If these same demographic patterns prove to be widespread among organisms in extreme environments, it may be possible to develop general recommendations for conservation of the biological resources of arctic and alpine ecosystems.

Age Distribution↗
PubMed2003

Life-history traits of the six Panonychus species from Japan (Acari: Tetranychidae).

Six species of the genus Panonychus are known from Japan. Life-history parameters of all six species were investigated at 25 degrees C, and for three species two strains of different geographical origin were included. The intrinsic rate of natural increase (r(m)) ranged from 0.172/day for the P. osmanthi albino strain to 0.209/day for P. citri, while the net reproductive rate (R0) varied from 23.98 in the thelytokous species P. thelytokus to 46.61 in P. citri. Both values were higher in the polyphagous species (P. ulmi, P mori and P. citri), which are considered crop pests, than those in the oligophagous species (P. thelytokus and P. osmanthi), considered non-pests. The only exception was P. bambusicola, an oligophagous non-pest species with R0- and r(m)-values closely resembling those of the three polyphagous species.

Animals↗