bluuebunny/crossref_metadata_2025 huggingface dataset:
Alternative models for species replacement of pelagic fishes
Authors: Matsuda Hiroyuki , Wada Tokio , Takeuchi Yasuhiro , Matsumiya Yoshiharu
Published: October 2006

It is well known that the stock abundance of a pelagic fish usually fluctuates and a species of pelagic fish which was dominant in abundance is often taken over by another species. Several alternative models for species replacement among pelagic fishes are presented and analyzed: (A) environmental fluctuation, (B) strong density‐dependent reproduction rate, (C) a two‐species system with phase variation (density‐dependent change of life history traits), (D) a two‐species competition system with environmental fluctuation, (E) cyclic advantage relationship among three competitive species, and (F) a two‐prey, one‐predator system. Different model requires different number of species for the occurrence of species replacement. Three criteria to test each hypothesis from qualitative properties of species replacement are proposed. Possible management policies to decrease the amplitude of stock fluctuations are discussed. As a result, if the catching effort to mackerels which is rare now is large, or if the catching effort to the sardine is still large when it begins to decline in stock abundance, fisheries may be strong destabilizing effect on the stock abundance.
Host‐feeding and oviposition by parasitoids in relation to host stage: Consequences for parasitoid‐host population dynamics
Authors: Kidd N. A. C. , Jervis M. A.
Published: October 2006

Among parasitoids which host‐feed destructively, there is a tendency for females to partition their feeding and oviposition behaviour in relation to different host stages, feeding preferentially or exclusively on earlier host stages and ovipositing preferentially or exclusively in (or on) later ones. We explored the dynamic implications of this behaviour for parasitoid‐host population dynamics, using modifications of the age‐structured simulation models of Kidd and Jervis (1989, 1991).

Using the new versions of the models, we compared the situation where parasitoids practice host stage discrimination with respect to feeding and oviposition, with the situation where they do not. Additionally, we examined the effects of host stage discrimination on populations by (a) having generations either discrete or overlapping, (b) varying initial age structure, (c) having varying degrees of density dependence acting on host adult mortality, and (d) varying parasitoid develoment times in relation to the length of host development.

With either discrete or overlapping generations of the host population, a reduction in the parasitoid development time had a destabilizing influence on the parasitoid‐host population interaction. With discrete generations stage discrimination had no effect on the risk of extinction, irrespective of either the degree of density dependence acting on the host population, or the initial age structure of the host population. When parasitoid search was uncoupled from the insect's adult energy requirements, the interaction was always unstable. With continuous generations, stage discrimination affected stability at certain parasitoid development times, but not at others. The relative lengths of parasitoid and host development times also influenced the tendency of the host population to show discrete or overlapping generations.
Dynamics of an enclosed population of pine mice, Microtus pinetorum
Authors: Gentry John B.
Published: October 2006

Enclosed populations of pine mice were studied over a 28‐month period and compared with populations in surrounding natural areas. The enclosed populations reached densities far greater than any observed in surrounding natural areas. It is suggested that the restriction placed on dispersal by the enclosure walls and the addition of food in the form of trap bait could have allowed the enclosed populations to reach higher densities than normally observed at SRP.
Estimation of the individual number entering each development stage in an insect population
Authors: Kobayashi Shiro
Published: October 2006

A method for estimating the number entering each development stage from data obtained by regular sampling through one generation of an insect population was described. This method is consisted of the following two procedures: The provisional estimates are calculated on the assumption that each stage has a common mortality in a sampling interval. Then these estimates are corrected on another assumption that the mortality is different in each stage but constant during a stage.

The result of testing its validity with two laboratory populations of the common cabbage butterfly, Pieris rapae crucivora, showed the availability of the present method.
Dynamics of distribution in animal communities: Theory and analysis
Authors: Tokeshi Mutsunori
Published: October 2006

Theoretical and analytical problems of the dynamics of distribution and abundance in animal communities were examined. In many communities, species with low abundance and of limited spatial occurrence (i.e., rare species) typically form a conspicuous peak when a frequency distribution of the number of species is constructed with respect to the proportion of sites occupied within an area of distribution. Models of distribution dynamics, including a new model proposed here, were compared with a range of animal community data using a new procedure to assess single‐ and bi‐modal patterns in frequency distributions of spatial occurrence. Data reveal that single‐modality with an excess of rare species occurs more frequently than bimodality. Even when bimodality is detected, the mode representing wide‐spread species is in the majority of cases smaller than that for rare species. Thus, a new model in which the rate of local extinctions is assumed to be negatively related to patch occupancy (or population abundance) is in better agreement with observed data than earlier models. Some problems of analysis, in particular model assumptions and testing, are discussed.
Management sampling for larvae of the colorado potato beetle
Authors: Binns M. R. , Mailloux G. , Bostanian N. J.
Published: October 2006

Untreated plot of ‘Kennebec’ and ‘Superior’ potatoes were sampled for Colorado potato beetle (CPB) at L'Assomption, Quebec, in 1982, 1986 and 1987. Numbers of CPB larvae per stalk were counted on 74 occasions for sample sizes ranging from 50 to 200 stalks. Regression techniques were used to estimate the relationship between mean and cumulative proportion of stalks infected. These were used to set up binomial sequential probability ratio test (SPRT) sampling plans for pest management decision making with tally numbers (or tally thresholds, cutoff numbers) equal to 0,1,…10. A binomial scheme defined by tally number equal to 4 is proposed for general use, and corresponding plans are given, with estimated operating characteristic and average sample number curves.
Model analysis of the effect of environmental fluctuation on the species replacement pattern of pelagic fishes under interspecific competition
Authors: Matsuda Hiroyuki , Wada Tokio , Takeuchi Yasuhiro , Matsumiya Yoshiharu
Published: October 2006

There are two factors affecting long‐term fluctuation of planktotrophic pelagic fish: environmental fluctuation and interspecific competition. Long‐term catch data of planktotrophic pelagic fishes in Japan suggest that the chub mackerel (species B) was replaced by the sardine (A), A was replaced by the anchovy, Pacific saury and horse mackerel (Group C), and species in group C were replaced by species B. If species A defeats B, B defeats C, and C defeats A in interspecific competitive ability, then the abundance of these three groups fluctuate forever and dominate in the same order. We call this cyclic advantage hypothesis for species replacement. In this model, environmental fluctuation affects the species replacement as a trigger. Environmental fluctuation does not determine the next dominant species but greatly affects when the next replacement occurs.
Persistence of females that produce only female progeny in lepidoptera
Authors: Ishihara Michio
Published: October 2006

In Lepidoptera females that produce only female progeny, can be found in wild populations of at least 11 species. The genetic variation is passed on to each generation of female offspring. If genetically abnormal females produce more female offspring than normal females do and mating is random, then populations containing these abnormal females will have a biased population sex ratio. Unmated females will increase due to the scarcity of males and so the population as a unit will die out. Several possible biological explanations for the persistence of the genetic variation have been proposed. But experiments and observations have not verified those hypotheses. Simulations of Heuch's model (1978), however, have shown that the variation persists if the population is distributed, in patches and there is dispersal among patches, even when insects disperse at random. Abnormal females tend to persist at both low and high migration rates, but the probability of persistence is higher at high migration rates. It has been suggested that abnormal females in a population are an adaptation, but the results of this investigation show that this explanation, may not be plausible.
Shift in life‐history strategy from reproduction to defense with colony age in the galling aphid Hemipodaphis persimilis producing defensive first‐instar larvae
Authors: Akimoto S.
Published: October 2006

Colony defense in some aphids is performed by sterile soldiers but in others by monomorphic larvae of a specific instar stage. This paper, focusing on a galling aphid Hemipodaphis persimilis with monomorphic defensive first instars, examined the mechanism by which the proportion of defenders is regulated in the colonies. Demographic analyses showed that the ratios of first instars (defenders) were kept constantly high (58% on average) from mid June to late September. High proportions of first instars could be explained by consistently high birth rates (birth rate hypothesis) or by a prolonged duration of the first instar stage (instar span hypothesis).

With the progress of colony age, the mature‐embryo content of apterous adults, used as an index of the birth rate, decreased and the proportions of advanced instars increased. These results did not support the birth rate hypothesis. By contrast, calculation of a newly proposed index, the molting rate, showed that the duration of the first‐instar stage was short in incipient galls but became longer with colony age. The duration of other instar stages was always kept short. These results corroborate the instar span hypothesis and suggest that the prolongation of the first‐instar stage is an adaptive mechanism by which the defender ratio is kept high in mature colonies where the birth rate is declining. The frequency of aggressive behavior in first instars increased from incipient to mature galls. Seasonal changes in the instar span and aggressiveness of first instars suggest that in H. persimilis colonies there is a strategic shift from the reproductive to defensive phase with colony age.
A measure of sexual selection for interspecific comparisons of species with diversified mating systems and different mortality schedules
Authors: Nishida Takayoshi
Published: October 2006

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.
New regression formula to estimate the whole population for recapture‐addicted small mammals
Authors: Tanaka Ryo , Kanamori Masaomi
Published: October 2006

We have devised a census formula of curvilinear regression suitable for capture‐recapture data of recapture‐addicted populations of the Japanese field vole (Microtus montebelli) obtained under a grid‐plan with single‐catch traps in order to estimate the whole population. The equation is founded on the assumption that the trappable population on the initial day is increased in way of an exponential curve until it reaches to the whole during one trapping period. The effect of trap‐preoccupation by marked and multiple collisions is considered in the formula. As a result of its application to field data of the vole, it has turned out that the equation is required for the data gained under the trapping plan with trap spacing 10m, but not for those under the plan with spacing 5m, to estimate the whole. A convenient method of analysis of the formula is offered here, but we have been yet unable to introduce assymptotic variance of estimates.
Sex ratios in laboratory and field populations of the old field mouse, Peromyscus polionotus
Authors: Smith Michael H.
Published: October 2006

Males outnumbered females as juveniles but not as adults among mice captured by hand in their burrows. The higher production of male offspring together with their higher mortality rate resulted in a 1∶1 sex ratio for the adult mice. Despite the equal abundance of each sex, more males than females were caught in traps. Males must have a higher chance of encountering a trap and/or of entering a trap after finding it.
The estimation of population density of the green rice leafhopper, Nephotettix cinticeps Uhler, in spring field by the capture recapture method
Authors: Nakamura Kazuo , Itô Yosiaki , Miyashita Kazuyoshi , Takai Akira
Published: October 2006

The population parameters of green rice leafhopper, Nephotettix cincticeps in hibernated generation was estimated by the capture‐recapture method on the gramineous weeds of resting paddy field from late in April to mid‐May, 1962–1965.

The difficulty of applying the capture‐recapture method to this insect is caused from the low density and the low activity of the leafhopper, so that it is necessary to make the suitable plan of capture‐recapture series and to construct the special method to detect the population parameters.

The number of adults differed greatly among the years and among the plots in the same year. But, in general, the density was relatively high late in April, and decreased rapidly in May. The number of males was higher than that of females late in April, but decreased rapidly to become lower in May.

The sampling efficiency with sweep‐net depends upon the many factors, such as weather and floristic conditions; especially the atmospheric temperature and the force of wind are considered to affect greatly to the efficiency. In general, low temperature and strong wind are the cause of low sampling efficiency.
Estimation of the stage‐specific survival rate in the insect population with overlapping stages
Authors: Kiritani Keizi , Nakasuji Fusao
Published: October 2006

An application ofHokyo andKiritani's method (1967) was attempted to estimate the stage specific survival rates of the population with overlapping stages. This method can be written as follows assuming a constant daily survival rate (K) throughout the life:
urn:x-wiley:14383896:pope0143:equation:pope0143-math-0001
where, and F refer respectively to the total incidence of ith instar nymphs and that of individuals after ith instar inclusive, and αi refers to the developmental period of ith instar.

Application of this model to caged and natural populations of the southern green stink bug, Nezara viridula, was made to test its validity. The estimates of the initial number of successive stages obtained from the present method were compared with those fromRichards andWaloff's method (1954) for the caged populations of 1st, 2nd and 3rd generations. The superiority of the present method to theRichards andWaloff's in estimating adult numbers was shown in all the generations examined. When different daily survival rates are involved in the course of population decrease, application of the revised method proposed byHokyo andKiritani (1967), gives much reliable estimate as compared with one before correction.

The present method is useful in constructing life table of such species as scale insects which complete their life cycle within a defined space, but their successive stages overlap considerably.
A statistical model of the reproduction of aphids
Authors: Shiyomi Masae
Published: October 2006

The logistic function has been generally used to describe the reproductive process of a “population” of animal. However, this model can not give us any information about the reproductive process of “individuals” in the population. In this study a statistical model on the basis of the reproduction of individuals of barley aphid is presented to find the proportion of the mature individuals, the heterogeneity in reproductive ability of the aphids, etc.

The model is constructed as follows:

The probability that j insects are found on a plant at time t0 is represented as Q(j).

The probability that h individuals of j have reproductive ability, say, mature individuals, in the period t0 to t1 is represented as B(h/j)=jChwh(1−w)j−h, where w is the proportion of mature individuals.

In a population with a homogeneous reproductive ability, the probability that each parent lays i offspring in the period t0 to t1 is represented as P(i/m)=e−mmi/i!, where m is mean. And, in a population, m changes according to the gamma distribution. Hence the probability that a parent lays i offspring between t0 and t1 is represented as , where p and k are parameters of negative binomial distribution. The probability that h parents on a plant lays s offspring is represented as .

From the assumptions mentioned above, the probability that s offspring are to be found at time t1 on a plant with the original j individuals at time t0 is represented byurn:x-wiley:14383896:pope0167:equation:pope0167-math-0003

The experimental populations were demonstrated to fit well to the model.
Population dynamics of the chestnut gall‐wasp, Dryocosmus kuriphilus Yasumatsu (Hymenoptera: Cynipidae) IV. Further analysis of the distribution of eggs and young larvae in buds using the truncated negative binomial series
Authors: Itô Yosiaki
Published: October 2006

Distribution pattern of eggs and the first instar larvae of the chestnut gall‐wasp, Dryocosmus kuriphilus, per bud of the chestnut tree was re‐examined using the truncatedPoisson and the truncated negative binomial series. The results are as follows:

About sixty percent of the distribution are approximated by the truncated negative binomial and another thirty percent by the truncatedPoisson. When the distribution has been approximated by the truncated negative binomial, the show scattered values, some of which are near thePoisson, but the mean value of is about 4 both in eggs and in the first instar larvae.

The number of buds which have not been infested by gall‐wasps is resulted from various factors as follows: (a) Buds formed after the laying activity of gall‐wasps has ceased; (b) Old and shrunk buds which were avoided in laying; (c) Buds in which eggs have died by the time of sampling; and (d) Buds escaping ovipositions by chance. Most of the gall‐wasp‐free buds located in the middle part of the shoot are accounted for the zero‐class expected by the negative binomial series.

Brass (1958) moment method for estimating parameters of the truncated negative binomial give good precision within the range of from 1 to 10 and of from 1 to 6.

It is concluded that the truncated distributions used are useful for the purpose of analysis of the distribution pattern of the chestnut gall‐wasp.
Why is there so much genetic variation for wing dimorphism?
Authors: Roff Derek A.
Published: October 2006

Wing dimorphism appears in general to be determined either by a single locus, 2 allele system in which brachyptery is dominant, or by the additive action of numerous loci. In the latter case studies indicate that the heritability is typically quite large. It is generally postulated that wing dimorphism is under strong selection: why then is genetic variation not eroded? In this paper I consider three possible explanations. First, genetic variation may not be exposed to selection because environmental heterogeneity effectively makes heritability zero. Because wing dimorphisms are known to evolve it seems unlikely that this is the primary factor. Second, directional selection on a threshold trait may push the population almost to monomorphism but erodes genetic variance at a very slow rate. This mechanism cannot preserve variation but makes it possible for other factors to more easily maintain variability. Finally, I demonstrate that in a heterogeneous environment spatio‐temporal variation in fitness will itself maintain a genetic polymorphism for wing dimorphism.
Wing dimorphism and the migratory syndrome: Correlated traits for migratory tendency in wing dimorphic insects
Authors: Fairbairn Daphne J.
Published: October 2006

The hypothesis that the morphological, physiological, and behavioral traits comprising the migratory syndrome in insects are genetically correlated through pleiotropic effects of genes controlling the titre of a common hormonal determinant is explored. Evidence that juvenile hormone (JH) influences the component traits of the migratory syndrome is presented, and thus JH is assumed to be the underlying, common determinant. However, readers are cautioned that this does not imply that JH is solely responsible for these traits, nor is this necessary for the arguments presented. For wing dimorphic taxa, the “correlated traits hypothesis” predicts covariance within wing morphs between JH titre and the proportion winged. Four simple genetic models for wing‐morph determination are considered: single‐locus with short‐winged (SW) dominant; single‐locus with long‐winged (LW) dominant; polygenic, fixed threshold, shifting distribution; and polygenic, shifting threshold, fixed distribution. In each case, wing morphology is assumed to be a threshold trait with the liability being JH titre at some critical stage of development. All models predict covariation between %LW and the mean JH titre of at least one of the wing morphs, but the form and direction of the relationship depends critically on the genetic model used. The results suggest that we should expect the traits associated with the migratory syndrome, and hence the trade‐offs associated with the evolution of wing dimorphism, to be correlated with proportion winged and, in this sense, to be frequency‐dependent.
Body mass changes in Trimeresurus flavoviridis (Viperidae) on Okinawa Island, Japan
Authors: Nishimura Masahiko , Kamura Takao
Published: October 2006

Body masses of wild‐caught habu, Trimeresurus flavoviridis, were measured with known error range. Habu larger than mature female size had steeper slope in length‐mass regression than smaller individuals. Females outweighed males in most snout‐ventlength classes and in early summer. Gravid females outweighed non‐gravid ones by about 20% on the average, but the body mass ranges of the two groups overlapped. Through the body mass change in mature females, the proportion of gravid females was estimated to be about 0.5.
Spatio‐temporal variation of natural and sexual selection in breeding populations of the coreid bug, Colpula lativentris (Heteroptera: Coreidae)
Authors: Nishida Takayoshi
Published: October 2006

Spatio‐temporal variations of lifetime reproductive succes (LRS) of both male and female individuals of a coreid bug Colpula 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.
Seasonal host alternation by the andromeda lace bug, Stephanitis takeyai (Heteroptera: Tingidae) between its two main host‐plant species
Authors: Tsukada Morio
Published: October 2006

I studied the seasonal occurrence of the andromeda lace bug, Stephanitis takeyai, on its two main host‐plant species. In a secondary forest in Kyoto, this bug altered its hosts seasonally, i.e., from an evergreen shrub, Pieris japonica, in winter to a deciduous shrub, Lyonia elliptica, in summer. In contrast, in Nara park where few L. elliptica were available, the bug exploited only P. japonica. Thus, seasonal host alternation by this bug is not obligate. A comparison of adult longevity and fecundity on the two host‐plant species demonstrated the higher quality of L. elliptica as a food resource. Corresponding to this difference in host quality, there was a dramatic difference in the seasonal population growth in the two study sites. In Nara, the population size at the beginning of the 2nd generation was almost the same as in the overwintered generation, whereas in Kyoto the population size in the 2nd generation was approximately one hundred times as large as in the overwintered generation. Thus seasonal host alternation is adaptive for the bug. In a previous study, I reported that overwintering as eggs in living leaves of their hosts is likely to be common among all the related species of this bug. Thus, this trait can be considered to be a phylogenetic constraint to the group. I speculate that host alternation by this bug has been derived because it is more adaptive from autoecy on an evergreen plant, similar to the pattern currently found in Nara, and that this bug can not only exploit deciduous host due to a phylogenetic constraint.
Persistence of abnormal females that produce only female progeny with occasional recovery to normal females in Lepidoptera
Authors: Ishihara M.
Published: October 2006

In Lepidoptera, females that produce only female progeny have been found in wild populations of at least 12 species. In some species, recoveries, where abnormal females return to normal females, have been observed. A mathematical model of the population dynamics with recovery was developed to identify the conditions for realizing the persistence of abnormal females. Analysis indicated normal and abnormal females coexist and reach an equilibrium state at certain recovery rate values. The equilibrium values of normal and abnormal females were determined. When a population was in equilibrium it was shown that the ratio of normal to abnormal females and the sex ratio after reproduction are always functions of the recovery rate and the proportion of female offspring from an abnormal female to that from a normal female. Using the simulation it was found that, even when a population fluctuates under variable environmental conditions, the two ratios mentioned above reach equilibrium. Equilibrium relationships were applied to published data, and it was concluded that recovery from abnormal to normal females explains the persistence of abnormal females in some species of Lepidoptera. The model developed in this paper can also be used for analysing the persistence of abnormal females of other insect species.
How is life history variation generated from the genetic resource allocation?
Authors: Tanaka Yoshinari
Published: October 2006

A simple quantitative genetic model is proposed to explain the observed genetic correlation structure of a bruchid beetle Callosobruchus chinensis in terms of two underlying variables: the resource acquisition and the resource allocation. Heritabilities and genetic correlations among age‐specific, fecundities are regarded as consequences of genetic variations of the two variables. Genetic correlations are predominantly positive in both predictions and observations. Nonetheless, comparison between observed and predicted values in heritabilities, genetic correlations, and genetic principal components suggested significant genetic variances both of the resource allocation and the resource acquisition. The prediction of the model is discussed in relation, to experimental tests of trade‐off in life history evolution.
Effects of parasitoid community structure upon the population dynamics of the honeysuckle leafminer, Chromatomyia suikazurae (Diptera: Agromyzidae)
Authors: Kato Makoto
Published: October 2006

Population dynamics of a leafminer, Chromatomyia suikazurae (Agromyzidae, Diptera) and its parasitoid community were studied for ten years at seven natural populations along an altitudinal gradient in Japan. This species which mines leaves of a forest shrub, Lonicera gracilipes (Caprifoliaceae), was attacked by 25 hymenopterous parasitoid species. Annually, the parasitoid community structure varied less within a population than among populations. The seven parasitoid communities were clustered into three groups corresponding to the altitudinal gradient: (a) lowland communities dominated by late‐attacking, generalist pupal idiobiont eulophids and with highest species diversity, (b) hillside communities dominated by an early‐attacking, specialist larval‐pupal koinobiont braconid and (c) highland communities dominated by an early‐attacking, generalist larval idiobiont eulophid. Annual changes of the host larval densities among the local populations were largely synchronous rather than cyclic. Among these populations, host density levels and mortality patterns greatly varied. By analyzing these inter‐populational differences of host mortality patterns, the following conclusions were drawn: (1) The host mortality patterns were determined by the host utilization patterns of the locally dominant species. (2) The host pupal mortality but not larval mortality was related to species diversity but not to species richness itself of each parasitoid community. (3) Density dependence was detected only in pupal mortality at a lowland population dominated by late‐attacking pupal parasitoids. These results suggest that interspecific interactions of parasitoids add additive effects to host population dynamics dissimilarly among local populations with different parasitoid communities.
Modelling selection for resistance to methods of insect pest control in combination
Authors: Barclay Hugh J.
Published: October 2006

The development of resistance to insecticides is now widespread among insects. Other methods of pest control are also potentially at risk of encountering resistance. A modelling approach is presented here to evaluate the effects of combining methods of insect pest control on the selection for resistance to the control methods. This analysis is based on partitioning the total mortality acting on a population into its constituent components from all known sources, and these are related to selection for resistance. When two control methods are used in combination, selection for resistance against the two is a linear function if the two don't interact, otherwise it may be sublinear or supralinear. A specific example is presented using a model of the Olive fruit fly (Dacus oleae Gmel.) and employing food‐baited and pheromone‐baited traps for control. The control methods that appear least likely to encounter resistance are natural enemies and the use of pheromone traps for male annihilation. These should be integrated into a control program where possible to minimize the development of resistance to other control methods being used.
Predator‐prey system structure in patchy and ephemeral phytotelmata: Aquatic communities in small aroid axils
Authors: Mogi M. , Sembel D. T.
Published: October 2006

Mechanisms allowing the persistence of an aquatic predator‐prey system in tiny pools (the mean ca. 0.5 ml) held by taro axils were analyzed from the viewpoint of temporal and spatial patterns of habitat use. Predatory larvae of a mosquito Topomyia tipuliformis concentrated in young axils, while 9 other taxa utilized both young and old axils or concentrated more in older axils. The total prey density was lower in axils with the predator but the density of each prey taxon (except for a few cases) and the number of prey taxa did not differ between axils with and without predators. This indicates that T. tipuliformis is a general predator and does not influence prey community organization through selective removal of particular prey taxa. Inter‐axil distribution of T. tipuliformis was aggregated in the first instar but uniform in the third and fourth instars due to intraspecific cannibalism, which assures the survival of a single individual under short food supply. Distributions of prey taxa were mostly aggregated, fitting the negative binomial distribution. Thirty seven out of 45 associations of 10 taxa were independent with 3 negative (between the predator and some late‐colonizing prey) and 5 positive (between some prey taxa) associations. Probabilistic refuges (produced by independent aggregated distributions) reduced interspecific encounters which may result in competition and predation, and thus probably facilitated prey coexistence. There was no evidence for the importance of predation in structuring the prey community. This system may be prey‐dominated in that predator persistence depends on prey community existence but prey community structure depends less on predation.
How an ant decides to prey on or to attend aphids
Authors: Sakata Hiroshi
Published: October 2006

The following results on the behavior decision making of the antLasius nigertoward two species of myrmecophilous aphidsLachnus tropicalisandMyzocallis kuricolaon chestnut trees have been found. (1) An individual worker consistently attended only one aphid species, even if her nestmates attended other aphid species on the same tree. (2) The ants preyed less on the aphid species which they attended than on other myrmecophilous aphid species. (3) The ants preyed less on the aphids which had been attended by their nestmates, even if both aphids were the same species. (4) The ants preyed less on aphids which had provided honeydew to their nestmates. (5) The increased aphid density per ant led to an increase in the rate of predation on the introduced aphids by the ants. These results suggest that each worker ofL. nigerchooses aphid species to attend from her experience. In addition, the workers can recognize whether an aphid has been attended by their nestmates and whether an aphid has given their nestmates honeydew. Through these processes, each worker decides to attend or to prey on the aphid. As a result, they may realize efficient collective foraging dependent on aphid density per worker.
Statistical study of Trichogramma brassicae efficiency in relation with characteristics of the European corn borer egg masses
Authors: Hawlitzky N. , Dorville F. M. , Vaillant J.
Published: October 2006

The efficiency of Trichogramma brassicae inundative releases in biological control of the European corn borer Ostrinia nubilalis was analyzed in seven plots of 504 plants, each situated in a corn field naturally infested by the European corn borer. Different strategies of Trichogramma releases were defined on the seven plots. These inundative releases were concluded to be highly efficient even on plots where there were either no parasitoid release or only one parasitoid release at the beginning of the egg mass laying period.
Survival rate and sex ratio in habu, Trimeresurus flavoviridis (Viperidae), on the subtropical Okinawa Island, Japan
Authors: Nishimura Masahiko , Kamura Takao
Published: October 2006

We examined the age structure and sex ratio of a viperid snake, Trimeresurus flavoviridis, based on samples collected by hand by local inhabitants, habu hunters and by baited traps in the middle and south of Okinawa Island, Japan. Small individuals had a low possibility of capture in all the collecting methods. The age structure was estimated through summing up the age frequency in each snout‐vent length (SVL) class in samples with a similar SVL structure. From the age structures, annual survival rates of adult females and males were estimated to be 0.7 and 0.8, respectively. In most samples the sex ratio was biased towards males, especially in March and August and in large individuals. However, the female proportion increased in June.
An experimental study on the foraging behavior of a pit‐building antlion larva, Myrmeleon bore
Authors: Matsura Toshiaki
Published: October 2006

Foraging behavior of a pit‐building antlion larva, Myrmeleon boreTjeder was investigated experimentally to elucidate the relation between the feeding level and pit relocation.

In artificial sands constructed in the field the 3rd instar larvae of M. bore rarely changed the positions of their pits, though several antlions had moved actively until they constructed pits. The average feeding rate was 0.3 prey/day/pit, and about 60% of prey captured were ants.

To examine whether or not M. bore larvae concentrate into the area where they can capture more prey, 8 antlions were released into each of 6 boxes filled with sand. I divided the sand surface of each box into two half areas, then gave prey to the pits built in a half area and gave no prey to the pits built in the other half. During the 50‐day observation period, nonfed antlions never moved into the area where prey were given.

The 3rd instar larvae were reared separately without food. Even under starved conditions they rarely relocated their pits until dealth. The average duration of survival period was 83.9 days.

The experimental results indicate that M. bore larvae adopt a tactic of sedentary ambushing. These larvae exhibit low movement rates which are independent of prey capture rates.
A laboratory study on the predatory mite Typhlodromus pyri (Acarina: Phytoseiidae): I. The effect of temperature and food consumption on the rate of development of the eggs and immature stages
Authors: Hayes A. J. , McArdle B. H.
Published: October 2006

Development periods were determined for eggs and juvenile stages of the predatory phytoseiid mite Typhlodromus pyri at four constant temperatures and three feeding levels. For the non‐feeding stages (eggs and larvae) power curve functions were fitted to development rate in terms of temperature. The results are compared to the general arthropod response to temperature. A non‐linear model was fitted to nymphal development rate in terns of temperature and food, in which the weight gain over an instar is assumed to be a linear function of daily food consumption. Examples of the same shape development rate—food relationship are given for two more phytoseiid mites and for other arthropods. The results are discussed with respect to T. pyri as an integrated control agent.
Morphometric variation within apterous females of Schizaphis graminum biotypes
Authors: Fargo W. S. , Inayatullah C. , Webster J. A. , Holbert D.
Published: October 2006

The occurrence of greenbug, Schizaphis graminum (Rondani), biotypes is a constant threat to the development and stability of pest‐resistant cereal crop varieties. Of the five biotypes (A, B, C, D, E) reported, only biotype B can be differentiated in life from the others by the physical characteristics of color. The other biotypes are differentiated on the basis of their ability to kill certain hosts or to withstand selected insecticides. The purpose of this research was to differentiate biotypes of apterous viviparous female greenbugs by multivariate techniques.

Appendages from individuals of biotypes B, C, and E were measured. Some of the characters including the length of first and fourth flagellar segments, profemur, mesofemur, mesotibia, metafemur and metatibia differentiated the biotypes in multiple comparisons in univariate analyses. Using discriminant functions based on within‐group covariance matrices, all greenbugs were classified into their correct group. The shortest Mahalanobis distance was between biotypes B and C. This suggests that biotype B is more closely related to biotype C than it is to biotype E. The coefficients of variation in the body measurements of biotype E were higher as compared to those of the other biotypes, indicating that a new biotype may evolve from biotype E in the future.
Stimuli governing intraspecific egg predation in the flour beetles, Tribolium confusum and T. castaneum
Authors: Craig David M.
Published: October 2006

The present research has not identified all of the factors that interact to produce the observed egg cannibalism rates in Tribolium. It has, however, shown that some physical and chemical properties of the egg and environment play an important role in determining cannibalistic activity in a population. Of general interest is the observation that cannibalism is not solely the result of the biological characteristics of the cannibal. While it is generally acknowledged that the quality and quantity of food may influence the intensity of cannibalism, it is not generally recognized that the environment can affect cannibalism in as complex a manner as is suggested by the current research. That two such closely related species, and even two life‐stages of the same species, may respond so differently to the same environmental cues is impressive. Predicting the intensity and hence the importance of cannibalism in natural populations may be difficult without detailed empirical studies.
One‐host one‐parasitoid system: Population dynamics of a zygaenid moth Pryeria sinica Moore in an undisturbed habitat
Authors: Shiotsu Yoshifumi , Tsubaki Yoshitaka
Published: October 2006

The population dynamics of Pryeria sinica was investigated in an undisturbed area in 1976–1979. We analyzed the process stabilizing the local population by the life table approach for immature stages and the mark‐recapture method for the adult stage. Females usually layed about 130 eggs in an egg‐mass. The shape of the survivorship curve was convex and was characterized by a relatively low mortality in the egg and larval stages and by a relatively high mortality in the prepupal and pupal stages. The low mortality in the early stage seemed to be not only due to the peculiar life cycle of this species (larvae develop in early spring when natural enemies are not active) but due to their protective nest‐webs, larval warning coloration and repellent smell. The high mortality after cocooning was caused by severe parasitization by Agrothereutes minousubae. The number of adult in the population varied by 2.10‐fold, which was less than that of other gregarious moths. The life table data and field observations suggest that adult female dispersal would have acted as a stabilizing factor, and A. minousubae as a conditioning factor on the dynamics of the moth population.
Arthropod predation limits the population density of an herbivorous lady beetle, Henosepilachna niponica (Lewis)
Authors: Ohgushi Takayuki , Sawada Hiroichi
Published: October 2006

The possible impact of arthropod predation on inter‐population variation in adult density of a thistle‐feeding lady beetle, Henosepilachna niponica (Lewis) was evaluated by means of predator exclusion experiments conducted in the field.

The population density of newly‐emerged adults at one habitat in the upstream area (site F) was significantly lower than at another in the downstream area (site A) although the egg density was nearly identical in the two habitats.

In the habitat with lower adult density, egg mortality was higher due to higher levels of predation. A predator exclusion experiment demonstrated that arthropod predation was the main factor causing high mortality during the immature stages, and physical factors such as heavy rains were unlikely to influence larval survivals.

Earwigs, ground beetles, predaceous stink bugs, and spiders were identified as the main predators in the study area. Of these, an earwig, Anechura harmandi (Burr) was more predominant than other predators and was significantly more abundant in the habitat with low adult densities.
Foraging behavior of individual workers and foraging dynamics of colonies of three Sumatran stingless bees
Authors: Inoue Tamiji , Salmah Siti , Abbas Idrus , Yusuf Erniwati
Published: October 2006

The foraging behavior of three stingless bees, Trigona (Tetragonula) minangkabau, T. (Trigonella) moorei and T. (Heterotrigona) itama, was studied to describe patterns of resource harvest in disturbed forest areas in Sumatra, Indonesia.

Average daily total number of foraging flights per colony was 1200 in T. minangkabau, 2400 in T. moorei and 7000 in T. itama and it was proportional to colony population size. Foragers collecting nectar, pollen or plant resin were respectively 70–80%, 10–20% and <10% in the three species. Pollen was collected most in the morning. Nectar collection peaked in midday in T. itama but continued almost evenly until dusk in T. minangkabau and T. moorei. Resin was collected evenly throughout day.

In all the three species the volume of a nectar load carried by a returning forager did not decrease until 1600, followed by slight decline. In the morning the sugar concentration of nectar was almost constantly 30%, and in the afternoon its maximum value reached 60% although some remained 30%. As a result, the mean sugar weight in a nectar load gradually increased until dusk.

In T. minangkabau, resin was collected by specialized foragers. Nectar foragers switched to collect pollen and vice versa. There were two types of foraging: “exploitatory” flights, the repitition of short, rather constant flights bringing back full resource loads, and “exploratory” flights, prolonged flight and/or reduction in amount of resources carried. Exploitatory flights followed the exploratory flights which led to discovery of rich sources. Mean duration of exploitatory flights was 7 min during nectar collection, 12 min for pollen and 23 min for resin. Sites of exploited flowers were estimated to be 84–434 m distant from the nest site. Mean duration of flights for nectar collection was 13 min in the morning and 6 min in the late afternoon.