A sequential estimation technique for capture-recapture censuses

A simple technique of sequential estimation was proposed for capture-recapture census by thePetersen method. In theory this technique makes it possible to secure automatically a required precision level for the population estimate to be obtained, irrespective of the population size. Some problems about its practical application were discussed.     

A further note on Kiritani and Nakasuji's model for stage-frequency data including comments on the use of Tukey's jackknife technique for estimating variances

Summary Some general equations for stage-frequency estimation are presented and their applications discussed.Tukey's (1958) jackknife technique is suggested for the calculation of the approximate variances associated with estimators of population parameters.     

Population dynamics ofTelenomus fariai (Hymenoptera: Scelionidae), a parasite of Chagas' disease vectors IX. Larval competition and population size regulation under laboratory conditions

Summary A series of experiments were carried out with the endophagous egg parasiteTelenomus fariai on its hostTriatoma phyllosoma pallidipennis to determine the possible role of intraspecific competition by the parasite progeny in population regulation of the parasite. Eight parasite densities (1, 3, 5, 10, 20, 30, 40, and 50 individuals per vial) were used, and the design of sequentially sacrificed replicates applied. Survivorship curves for each density indicated smaller number of progeny per host at higher densities, and the shapes of the curves suggested a relatively early mortality process.Morris' linear regression technique for determining within-generation density-dependence was used, and the results showed that only larval mortality could be identified as density dependent. The same technique applied within the larval stage proved that only mortality of larvae in their second, third, and fourth day of development were responsible for population regulation. The applicability of the technique, as well as the relevance of the results for natural population, is discussed.     

Population dynamics of houseflies,Musca domestica, on experimentally accumulated refuse

Summary The population dynamics of the housefly,Musca domestica, on patchy and unstable habitats consisting of refuse was investigated at a waste disposal site by using sticky flypaper and mark-release-recapture technique (Jolly-Seber's method). The newly disposed garbage was favorable for breeding of the flies for about one month after being disposed, while a mixture of garbage and ash from incinerated refuse was less favorable. On the garbage under favorable conditions, the rates of population increase was 1.25–2.82 per day, and approximately 1300–1500 flies were produced per square meter within the available period of one month. The rapid decrease in the fly density was observed just after the appearance of high density peaks. The mark-release-recapture study suggested that this rapid decrease would be mainly due to the density-dependent emigration of adult flies from the patchy habitats. The emigration was also activated when the time after garbage disposition became long.     

Anopheles subpictus Grassi: Observations on survivorship and population size using mark-release-recapture and dissection methods

Summary A mark-release-recapture experiment to estimate population survivorship and absolute size was performed with wild-caughtAn. subpictus adults at the village of Khano-Harni, Lahore District, Punjab Province, Pakistan during September 1978, the end of the monsoon rainy season, when temporal population abundance was maximized. Daily survival rate estimated from the recapture sequence of marked adults was low, males=0.192 and females=0.343. Survivorship for females estimated by several vertical age-grading procedures ranged from 0.347 to 0.628. Both stage- and age-specific life tables were calculated from vertical age-grading data determined by the dilatation method. Female and male population size was estimated byBailey’s modification of theLincoln Index and was found to average 4478.4 and 6106.8, respectively. The bionomics, survivorship and population size ofAn. subpictus in the Lahore are indicated that this species was probably not important in the transmission of human malaria.     

Further improvements to a method for analysing stage-frequency data

Summary An iterative procedure for correcting stage-frequency data is described to allow for situations where the period during which a population is sampled begins after some individuals have entered stage 2 or ends before all individuals are dead. The reason for correcting data in this way is to enableKiritani andNakasuji's method for estimating stage-specific survival rates, with extensions proposed byManly (1976, 1977), to be used to analyse the data. The proposed procedure is illustrated on data obtained by sampling a population of the grasshopperChorthippus brunneus passing through four instar stages to reach the adult stage.     

Time-specific life tables for the pea aphid,Acyrthosiphon pisum (Harris ), on alfalfa

Summary Time-specific life tables were constructed for three pea aphid,Acyrthosiphon pisum (Harris) (Homoptera: Aphididae), populations using a modification ofHughes' analytical procedure. All populations were studied on second-growth alfalfa (mid-June to mid-July) in south central Wisconsin; data for two populations were collected during 1980, and data for the third population were collected during 1982. The intrinsic rate of increase (r _m) estimated on a physiological time (day-degree) scale under field conditions but in the absence of natural enemies, provided a reliable estimate of potential population growth rate and was used in preference toHughes' approach of estimating potential population growth rates directly from stage structure data. Emigration by adult alatae and fungal disease were the major sources ofA. pisum mortality in each of the three populations studied. These factors were most important because of their impact on reducing birth rates within the local population. Parasitism was never greater than 9 percent. Mortality attributable to predation ranged from 0.0 to about 30.0%; however, even at the highest predator densitiesA. pisum populations increased exponentially.     

Life tables for worker honeybees

Summary Life tables for worker honeybees covering all life span, and those for adults, were prepared for three seasonal cohorts,June bees, July bees andwintering bees. Survivorship curves forJune andJuly bees show a convex type being exceptional for insects, with relatively high mortality at egg and feeding larval stages and at later adult stage after most bees became potential foragers. Adult longevity greatly lengthens inWinteriing bees and survivorship curve drops approximately with the same rate. A remarkable similarity of survivorship curves for men and honeybees was demonstrated, apparently due to highly developed social care in both. Some comments were given on mortality factors. The importance of life tables for population researches was shown by applying our result to the population growth curve made byBodenheimer, based upon the data byNolan. At the asymptote of the uncorrected curve, the ratio of total population estimated by uncorrected curve to that by corrected curve reaches about 3∶2. Contribution No. 821 from the Zoological Institute, Faculty of Science, Hokkaido University, Sapporo, Japan. Contributions from JIBP-PT No. 45. This study was in part supportod by a grant in aid from the Ministry of Education for the special project research, “Studies on the dynamic status of biosphere.” Population and bioeconomic studies on the honeybee colonies. II. We express our sincere thanks to Dr. YosiakiIt?, National Institute of Agricultural Sciences, Tokyo, for his kind stimulation and advices to the present work.     

Anopheles culicifacies giles: Adult ecological parameters measured in rural punjab province, pakistan using capture-mark-release-recapture and dissection methods, with comparative observations onAn. stephensi liston andAn. subpictus grassi

Summary Dispersal, immigration and emigration rates, horizontal and vertical survivorship and absolute population size were estimated for micropopulations ofAn. culicifacies, An. stephensi andAn. subpictus at a series of cattle sheds in rural Punjab Province, Pakistan, during November 1979 and May 1980 using capture-mark-release-recapture and dissection methods. Dispersal was temperature-related, with populations more vagile during May. Mean dispersal distance per individual was low for all species. More than 70% of all recaptures were taken at the point of release and the longest detected flight was 1250 meters. Horizontal survivorship was greater during November and was always less than vertical survivorship calculated from dissection agegrading data. Survivorship during the nulliparous period was greater than survivorship throughout total life, indicating the survivorship curve may be slightly sigmoid. Daily population sizes of endemic and immigrating females and males were calculated usingBailey's (1952) modification of the Lincoln Index, with the daily captures adjusted for immigration which was highest in May. Daily additions to the indoor resting population exclusive of immigrants were estimated using the method ofManly andParr (1968). The relationship of the present findings to malaria transmission and genetic control were discussed.     

A graphical model of disruptive selection on offspring size and a possible case of speciation in freshwater gobies characterized by egg-size difference

Summary The graphical technique devised bySmith andFretwell (1974) to construct a model of the optimal offspring size was applied to the case where disruptive selection might work on offspring size. On this basis, a possible case of speciation in freshwater gobies characterized by egg-size difference was discussed.     

Computing a population budget from sequentially sacrificed, replicated cultures

Summary When a population budget must be obtained from censuses based on replicated, sacrificed cultures, it is difficult to obtain estimates of transition probabilities and of the errors of such estimates, because there is no logical basis for pairing successive census counts. In a study of this nature estimating a population budget of immature stages of the housefly, the problem was solved by a randomization treatment of the original census results obtained at two densities. One hundred randomly generated census matrices over all census times for each density were smoothed to remove the effects of sampling error and a population budget constructed according to defined rules. Transition probabilities computed from the population budget were plotted on triangular coordinate paper and mean probabilities, 95% confidence regions for these means, and 95% equal frequency ellipses computed. All computations and the graphing of the results were carried out on a digital computer. The computer program, available from the authors, is written in FORTRAN IV and could be easily modified for similar studies. Contribution No. 1364 from the Department of Entomology, The University of Kansas. This study has been supported by the Medical Research and Development Command of the Office of the Surgeon General of the Army under contract No. DA-49-007-MD-738, U.S.A. and by a Public Health research career program award (No. 3-K3-GM-22, 021-01S1) from the National Institute of General Medical Sciences, U.S.A. to RobertR. Sokal. It was carried out during the tenure of a National Science Foundation predoctoral fellowship by EdwinH. Bryant. The authors appreciate the help of Dr.F.J. Rohlf with computational aspects.     

Comparison of male adult population densities of the oriental and artocarpus fruit flies,Dacus spp. (Diptera: Tephritidae), in two nearby villages in Penang, Malaysia

Summary The populations of native male adult oriental fruit flyDacus dorsalis (Hendel) and artocarpus fruit flyD. umbrosus (F.) in two selected site (BU and SD) were estimated weekly by the capture-recapture technique using live traps baited with methyl eugenol. In BU where many varieties of fruit trees were grown, the estimated population densities ofD. dorsalis were between 980 and 3100 male flies per ha between May and July, 1984. During the same period, in SD where there were fewer number and varieties of fruit trees, the estimated population densities were between 300 and 1000 flies per ha. The estimated population densities ofD. umbrosus over the same period were between 570 and 1290 flies per ha in BU; and between 5 and 95 flies per ha in SD. Of a total 6828 markedD. dorsalis flies released only one fly (released 6 weeks earlier in BU) was caught in a different site.     

Population studies ofBrevicoryne brassicae (L.), its parasites and hyperparasites in England

Summary Studies on populations ofBrevicoryne brassicae (L.), its parasites and hyperparasites were carried out by actual counting in the sprouts field and by sticky and water traps.B. brassicae was found to be attacked by one primary parasite,Diaretiella rapae (McIntosh), which in turn is parasitized byAlloxysta brassicae (Ashm.),Asaphes vulgaris Walker,A. suspensus (Nees),Pachyneuron minutissimum (F?rster) andDendrocerus carpenterii (Curtis). The aphid population in the field was started by immigrant alates which were found flying too early to be synchronized with the sprouts plants. SimilarlyD. rapae was not synchronized with the aphids although many individuals could have been carried into a plot through parasitized immigrant alates, of which less than 30% were found parasitized. Because of high hyperparasitism (especially byA. brassicae)D. rapae was not able to maintain a high rate of parasitism to curb the aphid population growth. The maximum percentage mummies being 27.8%, while the maximum, percentage parasitism being 56.6% recorded only during the early 1974 season (mean=12.9%). The decline of aphid population from September onwards was largely due to the cold weather, Syrphid predation and occasionally fungal attack. The high rate of hyperparasitism byA. brassicae is attributed to its better synchronization withD. rapae. The mean percentage of parasite that emerged from mummies collected during 1973–74 wereD. rapae 31.3%,A. brassicae 64.3%,A. vulgaris andA. suspensus 4.3%,D. carpenterii 0.2% andP. minutissimum 0.1%.     

Population growth trends in India: 1991 census

The decennial census counted the total population of India at 843.931 million as of the sunrise of March 1, 1991. The total is 160.6 million higher than that of a decade earlier in 1981. The actual census count exceeded by 45 million the official projections for 1991 based on the 1971 census. However, the official projections for the same year based on the 1981 census fell short by 7.6 million only. Most of the observed differences are explained by the slower decline in the fertility levels. The population growth ratepeaked during 1971–81, perhaps in 1972–73 (based on the Sample Registration Scheme data). The average annualexponential growth rate declined marginally to 2.11 per cent (4.5%) after having remained at a plateau for the previous two decades of 1961–71 and 1971–81. At this point in time, the fertility and mortality trends indicate that India will reach the replacement level fertility [Net Reproductive Rate of Unity] by the years 2010–2015. It can be said with a greater degree of certainty that the official target of reaching the replacement level fertility by the year 2000a.d. will not be reached. Based on the 1991 census results, it can be said that India will reach the billion mark by the turn of the century. The World Bank projects a population of 1,350 million by the year 2025a.d., and a stationary population of 1,862 million by the year 2150a.d., assuming that the replacement level fertility [Net Reproductive Rate = 1] in India is reached about the year 2015a.d.     

Dispersion analyses and resource utilization of aphid parasitoids in a non-depletable environment

Summary Dispersions and resource utilization of primary and secondary parasitoids developing in non-depletable primary host populations were determined for an aphid-parasitoid community occurring on strawberries. Analyses of dispersions based onGreen's coefficient andLloyd's Patchiness Index indicated parasitized aphids were highly aggregated initially, became less aggregated as density increased, and remained aggregated following collapse of the aphid populations. The “index of aggregation” values calculated usingTaylor's Power Law concurred with results from the other indices, and the similarity of the regression coefficients from both seasons suggests that the index of aggregation may be characteristic for communities as well as species. Analysis withIwao's regression of mean crowding on the mean generated similar results when population data were stratified temporally, and also indicated that the individual was the basic unit of the population. In a non-depletable environment, oviposition of individuals exhibiting an aggregated dispersion pattern within clumps of hosts provides primary parasitoids with a suitable trade-off between energy utilization or genetic potential, and losses associated with hyperparasitism.     

Population biology of the broad-horned flour beetle,Gnathocerus cornutus (F.) II. Crowding effects of larvae on their survival and development

Summary Crowding effects of larvae on survival and development were examined for the broad-horned flour beetle,Gnathocerus cornutus (F.). The larvae matured about 3 weeks after hatching regardless of their densities, but pupation was severely hindered by crowding. There existed an upper limit for the number of the pupae produced and its mechanism was studied by a statistical analysis of the distribution patterns of pupal cells and the experiment in which glass tubes were artificially supplied in addition as pupation site. These studies show thatG. cornutus larvae have a habit to construct cells for pupation and this habit leads to a contest competition for pupation site at high densities. The significance of the contest competition for population regulation was discussed comparing the results onTribolium confusum Jacqueline duVal.     

Selection for divergent emigration rates in laboratory populations ofMusca domestica

Summary High and low emigration rates through a laboratory system were selected for in populations of house flies (Musca domestica L.). Emigration consisted of movement of flies from on plastic box to another by way of a connecting tube. Selection was carried out by first dividing a wild population of flies into two lines and then selecting for movement from the box in one line and against movement from the box in the other line. The selection experiment was performed twice. In both experiments a statistically significant difference between the two strains was obtained in three to four generations of selection. In the second experiment, after 5 genrations the mean number of high emigration rate flies emigrating in 1 hour was 4.37 times the mean number of low emigration rate flies and in 24 hours was 2.81 times the number of low emigration rate flies. The second experiment was terminated after 6 generations, but the first experiment was continued for 35 generations. In this case, divergence ceased in roughly 15 generations. The possible relevance of the findings to laboratory population experiments in which spatial discontinuities are included is discussed. This study was supported by a research grant of the National Science Foundation (Environmental Biology GB 4567) to Prof. DavidPimentel. The author wishes to thank Prof.Pimentel for his aid and encouragement.     

A population study ofStenocranus minutus (Fab. ) (Hemiptera: Delphacidae)

Summary The seasonal and annual fluctuations in a population of the delphacid,Stenocranus minutus (Fab.) onDactylis glomerata L. were studied from March 1968 to September 1970. The study involved the comparison of several sampling methods to estimate the egg, nymphal and adult numbers and an investigation into causes of mortality within each stage. A population budget was made for the years 1969 and 1970.