Impact of developmental variance on behavior of models for insect populations I. Models for populations with unrestricted growth

The concept of developmental variance is discussed with reference to its use in models for insect populations. When included in a model, developmental variance is typically used to describe the variation of developmental periods among individuals. However, its presence in a model can also have indirect impact on survival and fertility schedules. This impact can lead to significant changes in population growth rates and generation times. These relationships between developmental variance and population growth in models are quantified and discussed.     

Extensions to Kiritani and Nakasuji’s method for analysing insect stage-frequency data

Summary There is evidence that the simple method ofKiritani andNakasuji (1967) for the analysis of insect stage-frequency data produces estimates of stage-specific survival rates that compare well with the estimates from more complicated methods (Manly, 1975). However the method as originally proposed byKiritani andNakasuji cannot always be applied because it assumes that the insect population involved was sampled at regular intervals of time. Furthermore, parameters such as the durations of stages are not estimated. In this note modifications to the basic method are suggested with the idea of overcoming these limitations.     

A model for analyzing insect stage-frequency data when mortality varies with time

A model is developed for the analysis of insect stage-frequency data which may be applied to populations with age-dependent mortality. The analysis of stage-frequency data is divided into two steps. In the first step, the number of different mortality rates and their values are estimated. The second step provides estimates of developmental rates and variances for each developmental stage and in addition provides estimates of the number of recruits to each stage. The model may be used both in analysis and prediction of insect stage frequencies. Hence, in addition to estimating developmental and mortality rates from stage-frequency data, it may also be used as a simulation model for an insect population. The model is applied to two populations of Hemileuca oliviaeCockerell , a lepidopterous pest of New Mexico grasslands. The model identifies, in the two populations, different mortality rates that are related to plant productivity.     

Impact of developmental variance on behavior of models for insect populations II. Models for populations with density dependent restrictions on growth

The impact of variation in developmental times on behavior of models for insect populations is investigated with special reference to models which include various types of intraspecific competition. At low densities, increases in developmental variation led to decreases in reproductive rate. At high densities, increases in developmental variation led to increases in reproductive rate. There was little change in the relationship between developmental variance and generation time as density increased.     

Application of a marking-and-recapture method for the analysis of larval-adult populations of an insect,Nezara viridula (Hemiptera: Pentatomidae)

Difficulty arises in applying marking-and-recapture methods to insects when the probability of recapture of marked individuals is changed with advancing age, either due to detachment of the mark by moulting (in the case of larvae) or to changes in their survival rate or their behaviour. A modification of the re-recapture method (Leslie et al., 1953) has been devised to analyze the capture-recapture data of the 5th-instar larvae and adults of Nezara viridula L. Estimation of the rate of moulting to the adult stage is made with the aid of additional information on larval survival. Migration rates of the larvae between the two halves of the census field is estimated byIwao's (1963) method. Through these analyses, the dynamic feature of the population during transition from the 5th instar to, adult is revealed. Several problems involved in the application of marking-and-recapture methods to insect populations are discussed.     

昆虫多状态发育的生存分析

针对昆虫种群变态发育过程,本文给出了一个多状态生存函数的模型。使用生存分析的方法对模型进行丁分析。本文还对有关的生存参数如各状态的死亡风险,发育风险,年龄特征死亡率,年龄特征发育率以及状态发育历期等进行了讨论并且给出了它们的极大似然估计值。关于马铃薯块茎蛾数值例子的分析表明所提出的摸型用来描述昆虫种群的发育过程是有效的。本文的结论可以做为组建描述昆虫种群多状发育的年龄一状态特征生命表的理论基础。     

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

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.     

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.     

A method for estimating natural survival rate and mean fecundity of an adult insect population by dissecting the female reproductive organs

Several problems were discussed in relation toMacDonald' s method (MacDonald , 1957) for estimating the survival rate of a natural population of adults with varying survival rates and unstable age structure.

1. Random samplings with a fixed sampling ratio and an appropriate census interval is pre-requisite during the occurrence of the adults.
2. At each sampling, female adults are dissected to know the ratio, p_i, of nulliparous females in ith sample (i=0, 1, 2, 3, …,). The Σn_ip_i/Σn_i gives an estimate of the ratio, Fα/F, of nulliparous females in the population where n_i refers to the population size on ith census date. If a constant daily survival rate is assumed, the daily survival rate is estimated from equation (4′). When the survival rate is not constant over the period of adult occurrence, e. g. before and after the initiation of oviposition, the survival rate during pre-ovipositional period is estimated by equation (4″).
3. Decision of an economic census interval to obtain a reliable estimate of the ratio, Fα/F, is depending on the form of emergence curve, particularly on its duration and the length of pre-ovipositional period. If the normal distribution can be assumed for the emergence curve, an interval less than one third of the emergence period is recommended. Concerning with insects having a long pre-ovipositional period, a census interval which exceeds one third of the emergence period still gives a good estimate of Fα/F.
4. The mean realized fecundity of some kind of insects can be estimated by equation (5′ or 5″) using the estimates obtained by the present method.

     

A simulation study of population interaction between the greenhouse whitefly,Trialeurodes vaporariorum Westwood (Homoptera: Aleyrodidae), and the parasitoidEncarsia formosa gahan (Hymenoptera: Aphelinidae) I. Description of the model

A simple simulation model was developed to simulate the population dynamics of the system of the greenhouse whitefly (Trialeurodes vaporariorumWestwood ) and the parasitoid Encarsia formosaGahan . On the assumption that temperature is constant, the whitefly population was described as theLeslie Matrix model. Parasitization and host feeding by the parasitoid population were modelled by means of a modified disc equation. The validity of the model was demonstrated by comparing the predictions of the model with the observed values obtained in greenhouse experiments.     

Use of a general model to examine control procedures for a cockroach population

A matrix model for populations is described. The model breaks the population into an appropriate number of stadia to allow for reproductive cycles and includes individual daily survival rates and simple density dependence together with migration. Mortality due to insecticidal treatments may be applied on specified days to simulate space spraying while residual insecticides may be simulated with constant or declining effect. The use of the model is exemplified using a simulated population of Blattella germanica with various treatment regimes. This simulation emphasised the importance of immigration.     

On the nature of errors involved in estimating stage-specific survival rates by Southwood's method for a population with overlapping stages

This paper has examined the effect of within-stage mortality on the estimation of stage-specific survival rates bySouthwood's (1978, p. 358) method. As pointed out bySouthwood , both the severity and timing of mortality affect the mean duration of a life stage, and consequently the estimate of the number of individuals entering that stage. Knowledge of the form of the survivorship curve permits correction of the estimate under certain circumstances. The use ofSouthwood's method with two overlapping stages having different rates and patterns of mortality leads to complex errors in the estimation of survival for the first stage. The nature of these errors is examined analytically and via a simulation model.Southwood's method is fairly robust, with moderate differences in mortality rates leading to acceptable errors in estimating survival for the first stage. When both the rate and pattern of mortality in both life stages are the same, then the survival estimate is made without error. Precise estimates of stage-specific survival will not usually be possible withSouthwood's method because of the errors introduced by the very parameters being measured. Direct measurement of mortality rates and survivorship patterns (seeSouthwood , 1978, p. 309) is strongly advised, at least in preliminary work.     

Factors influencing development and survival ofCulex pipiens pallens larvae (Diptera: Culicidae) in polluted urban creeks

Factors influencing development and survival of Culex pipiens pallens immatures in polluted urban creeks were studied in Saga, Japan. Addition of food shortened developmental durations and increased pupal size in floating cages at only the least polluted site out of 4 study sites. There was no evidence for developmental delay due to overcrowding in natural populations. Survival was not increased by artificial feeding at any site. Using the developmental parameters obtained for caged cohorts, survival in natural populations was estimated from differences between the actual number and the expectation if there were no mortality. Pupation rates ranged from 1> to >10% by site and season. Mortality due to predation, evaluated from the difference in pupation rates between caged and natural populations, exceeded 30% in 4 out of 6 cases (twice at 2 sites and once at the other 2 sites). Lethal factors in the creek water caused the predominant mortality in 2 other cases. Regulation of C. pipiens pallens population breeding in eutrophic, open creeks was discussed in the context of larval dispersal through behavioral interference.     

The estimation and simulation of variable developmental period,with application to the mosquitoAedes aegypti (L.)

The variability of stage developmental period may be a seminal feature of some insect populations and therefore of importance in management studies. A transfer function technique is described for estimating the frequency distribution of developmental period and simulating the subsequent population dynamics. The technique relates recruitment time series of consecutive stages by an age-specific developmental success function. Approximate statistics, such as the mean, median or mode developmental period, may be determined and the effect of different temperature or density regimes compared.     

Analysis and simulation modelling of population dynamics and bioenergetics ofCryptolestes ferrugineus (Coleoptera: Cucujidae) in stored wheat

The consequences of infestation of stored wheat by the rusty grain beetle, Cryptolestes ferrugineus (Stephens) was determined for 222 d at 30°C in 70-1 drums containing wheat at 13.5% moisture content. Temperature, grain moisture, seed damage, germination and weight, dust weight, fat acidity values (FAV), published data on growth, reproduction, survival and cannibalism rates and energy budget were used to develop a computer simulation model to simulate the population dynamics of C. ferrugineus at 30°C. In the insect-free control system, the fungi, Alternaria alternata decreased, Aspergillus glaucus group and Penicillium spp. increased, probably causing a rise in FAV of the grain. In the insect-infested system, C. ferrugineus could only eat the wheat germ of kernels that had a broken bran layer; 35.7% of the wheat germ or 914.6 J per 100 kernels was consumed. Within two generations after initial introduction, C. ferrugineus reached a peak in numbers and biomass polluting the ecosystem with excreta and remains, and accelerating the deteriorative process observed in the insect-free control system by increasing respiration temperature, FAV and reducing grain germination. After 87 d, the insect population declined to low levels. The simulation model provided a close match between the observed and predicted numbers of insect life stages and bioenergetic variables during the insect population growth phase. Simulation trials suggested that cannibalism of larger compared with smaller immature stages would be more wasteful of developmental time and energy, reducing the number of individuals reaching reproductive age, and that density-dependent fecundity was probably not an important regulatory mechanism of C. ferrugineus population dynamics in this study.     

Population dynamics of the japanese clouded apolloParnassius glacialis butler (Lepidoptera: Papilionidae). I. changes in population size and related population parameters for three successive generations

1. Population dynamics of a univoltine butterfly Parnassius glacialis (Lepidoptera: Papilionidae) was studied with mark-recapture methods for three successive generations in a hilly region in Kanazawa City, Ishikawa Prefecture, Japan in 1981–1983.
2. Jolly (1965) andSeber's (1973) method was applied to the mark-recapture data to estimate population parameters (daily survival rate, longevity, population size, sex ratio, etc.).
3. Sampling ratios were at least 50% and 30% for males and females, respectively.
4. Mean daily survival rate for males ranged 0.81–0.86 and that for females 0.80–0.84. Mean longevity was about 4–7 days for the males and about 5 days for the females. Spiders killed more males than females. Maximum longevity for an individual recorded during the study was 31 days for males and 18 days for females.
5. Emergence of the butterflies was later and less synchronous in 1981 than in 1982 and 1983. This was thought to be due to later extinction of heavier snow in 1981 than in the other years.
6. The population remained relatively stable for the three successive generations, with estimated total numbers of 914, 1277, and 869.
7. Estimated sex ratio (% females) was 30–40% at emergence

     

Population regulation of a mosquitoArmigeres theobaldi with description of the animal fauna in zingiberaceous inflorescences

1. Inflorescences of some Curcuma and Zingiber (Zingiberaceae) in tropical Asia provide an unique aquatic habitat being discrete, small, and made of numerous smaller compartments (the bracts).
2. The aquatic community in inflorescences of Curcuma in northern Thailand was composed of immature Diptera, of which the biting midge Dasyhelea and the mosquito Armigeres theobaldi were the commonest. No important competitors, predators or pathogenic parasites for the mosquito were confirmed.
3. Inter-inflorescence distribution of the mosquito was contagious. Within each inflorescence, the fourth-instar larvae or pupae usually occupied bracts singly.
4. The k-value analysis detected density-dependent mortality due to contest competition in the mosquito larvae.
5. Variations in the larval and pupal mosquito size were density-independent and remarkably small as compared with size variations known for other mosquitoes.
6. These population attributes (large density-dependent mortality with density-independent, minimally variable individual size) appear unique among mosquitoes, arising from conspecific killing, efficient foraging (inter-bract movement by crawl and single occupation of bracts), and availability of host plant tissues as supplementary food.
7. A simple population model suggested that a small proportion of adult females lay eggs.

     

Population dynamics ofLuehdorfia japonica Leech (Lepidoptera: Papilionidae)

1. An adult population of a papilionid butterfly, Luehdorfia japonicaLeech , was studied by marking, release and recapture procedures in a hilly region in the suburbs of Kanazawa City, Japan.
2. Age of butterflies was estimated from the wing wear conditions, rated as winage categories 0 to 6.
3. Jolly (1965) andSeber's (1973) method was applied to the marking-recapture results for estimating the population parameters (sampling ratio, population size and survival rate).
4. Sampling ratio of males was consistently higher (around 50%) than that of females.
5. Newly emerged females were especially inactive, so that few of them were captured. From day 6.5 to day 10.0 they began to oviposit and became more active and more catchable.
6. An approximate sex ratio of 1∶1 was confirmed from the specimens collected in the field and by rearing experiments.
7. Daily survival rate was about 0.75–0.80 and mean longevity was about 4 days for both sexes. The maximum longevity observed was 17 days, for males and 21 days for females.
8. Dispersal by both sexes of the butterfly was more than 1 km.