bluuebunny/crossref_metadata_2025 huggingface dataset:
Reproduction and egg diapause of the oriental chinch bug, Cavelerius saccharivorus okajima (Heteroptera: Lygaeidae), in the subtropical winter season in relation to its wing polymorphism
Authors: Fujisaki Kenji
Published: October 2006

Reproduction and egg diapause of the oriental chinch bug, Cavelerius saccharivorus, in the subtropical winter season were investigated in relation to its wing polymorphism. Macropterous females collected from the southern part of Okinawa Is. in the autumn season delayed their oviposition and were less fecund early in the adult life period, but survived much longer than brachypterous females collected from the same locality. The total fecundity was not significantly different between wing morphs. The diapause of eggs laid by brachypters tended to be terminated more easily at a high temperature than that of eggs laid by macropters. This indicated that the eggs laid by macropters were more intense in their diapause than those laid by brachypters. However, irrespective of the parental wing form, diapause showed considerable variation in its intensity within and between clutches.
Lek mating system and its impact on male annihilation technique
Authors: Horng Shwu‐Bin , Plant Richard E.
Published: October 2006

Simulation models were presented which describe the matings inside a lek. The size of the lek was assumed to follow a poisson distribution, the dominance factor of each of the males was drawn from a gamma distribution, and the mating probability for each male was determined by its mating effectiveness raised to female mating factor divided by the sum of all the mating effectivenesses raised to this power. The mating probatility for each male and the actual matings were determined by Monte Carlo simulation. Based on the simulation data, the effects of female mating factor and size of the lek on the frequency of actual matings accomplished by the males inside the lek were discussed. In the case of male annihilation, the mean number of effective matings per male in the lek, calculated from the frequency of actual matings weighted by the effective mating ratio, was used to evaluate the efficiency of male annihilation method.
Theoretical consideration of effect of fishing mortality on growth and reproduction of fish populations
Authors: Hiyama Yoshiaki , Kitahara Takeru
Published: October 2006

An increase in fish mortality due to fishing can theoretically change the growth and reproduction of fish populations from the viewpoint of adaptation. We address the issue of how an iteroparous fish should convert surplus energy into somatic growth and reproduction at each age under given conditions of mortality. A model of life history, which maximizes the net reproductive rate using the discrete maximum principle, is improved employing a new relationship between body weight and surplus energy which we have recently proposed. The model is applied to the North Sea plaice Pleuronectes platessa, for which it has been reported that the average length of young fish had increased whereas that of old ones had decreased for some decades. Although the model cannot directly explain the former phenomenon, the two phenomena can be interpreted as a change in the optimal life history due mainly to an increase in mortality.
Genetic correlation of wing polymorphism between females and males in the oriental chinch bug, Cavelerius saccharivorus Okajima (Heteroptera: Lygaeidae)
Authors: Fujisaki Kenji
Published: October 2006

Genetic correlations of the wing form and the relative wing length between females and males were estimated in the oriental chinch bug, Cavelerius saccharivorus, by calculating the correlation between the sexes of the proportion macropterous or the mean relative wing length in full‐sib families obtained from different wing forms of parents emerged in a high density population. There was a significantly positive genetic correlation between the sexes in both the proportion macropterous and the mean relative wing length. However, the appearance rate of macropters tended to be much lower in males than in females under the rearing conditions which promote the appearance of macropters. This was evident especially in the offspring of brachypterous parents. These indicated that in C. saccharivorus the wing polymorphism of males is not a simple result of the genetic correlation of wing morphology between the two sexes. It was considered that both of the female and male fitness advantages to wing reduction, as well as the genetic correlation between the sexes, would influence the evolution of wing polymorphism in this species.
Relative humidity as an environmental factor determining the microhabitat of the nymphs of the rice brown planthopper, Nilaparvata lugens (Stål) (Homoptera: Delphacidae)
Authors: Isichaikul Somchai , Ichikawa Toshihide
Published: October 2006

Microhabitat of the nymphs and the adults of the rice brown, planthopper, Nilaparvata lugens is known to be the lower parts of rice plants. In this study, possible environmental factors determining the range of the microhabitat were experimentally analyzed by using the nymphs under laboratory conditions. Thirty individuals of the 1st or the 3rd instar nymphs were released to a potted rice plant covered with a transparent acrylic cylinder. When the top of the cylinder was kept opening (open condition), the temperatures in the cylinder were almost constant, and relative humidities in the cylinder decreased with the increase of the height from the water surface of the pot. In the open condition, most nymphs and all exuviae were found on the basal parts of rice plants where the humidity was more than ca. 90% r.h. When the top of the cylinder was kept closing with parafilm (closed condition), the temperatures in the cylinder were almost constant, and relative humidities in the cylinder were more than 95% r.h. In the closed condition, the nymphs and the exuviae were distributed sparsely to the whole parts of rice plants. In both of the open and the closed conditions, patterns of nymphal distributions on rice plants during the dark regime were the same as those during the light regime under 25±2°C and 16L∶8D. Four different temperatures ranging from 20°C to 35°C did not influence on the microhabitat in the open condition. It was concluded from the results that relative humidity is the important environmental factor to determine the microhabitat of the nymphs of N. lugens which showed to prefer very humid condition more than ca. 90% r.h.
Breeding and egg survival of a population of a salamander, Hynobius nebulosus tokyoensis Tago
Authors: Kusano Tamotsu
Published: October 2006

A population of a salamander, Hynobius nebulosus tokyoensisTago was studied at Habu, Hinodemachi, in Tokyo during the breeding seasons from 1976 to 1978. Adults appeared in the pond were captured and marked individually by toe‐clipping. Egg sacks were counted and tagged with vinyl tapes for the marking.

The annual egg production of this population was found to be constant, about 6500 eggs, and total number of breeding adults appeared in the pond also varied little during three years.

The appearance of breeding adults in the pond and oviposition seemed to be influenced by the rise of temperature and rainfall.

Males appeared earlier in the pond and stayed there for approximately 10 to 20 days. On the other hand, females appeared later in the pond and left there soon after laying eggs.

Mean clutch size and body length of breeding adults appeared in the pond showed a tendency to decrease as time proceeded, which seemed to show that the smaller and younger the salamander was, the later it appeared in the pond.

Owing to low temperature, the eggs laid earlier took more time to hatch than those laid later.

The survival rate of eggs was 67.2% in 1976, 86.4% in 1977 and 81.2% in 1978. The loss rate of eggs laid in the early and late periods of oviposition was higher than that of eggs laid in the middle period.
The population characteristics of the East African red legged diplopod Metiche tanganyciense Kraus (Diplopoda: Spirobolidae)
Authors: Banerjee Barundeb
Published: October 2006

A marked variation exists in the numbers and distribution of East African red legged millipede Metiche tanganycienseKraus on the surface and in the lower layer (15 cm) of the soils. Stadia 5 cm and lesser in length are found in the lower layer and those 5 cm and above on the surface soil. Adults are common in varying numbers in both the habitats.

It is suggested that after becoming surface active during March–August, and mating, adults migrate to lower layer during September to oviposit. Eggs and early developmental stages are passed here, and when they are 5 cm in length, the stadia move to the surfface soil to complete their development. In keeping with this behaviour, spatial distribution of the adults may change from non‐aggregation on surface soil to aggregation in the lower layer. The simulataneous presence of adults and developing stadia in the two habitats suggests and overlapping of generations.
A model descriptive of gregariousness of colonial insect larvae
Authors: Tsubaki Yoshitaka , Yamamura Norio
Published: October 2006

A model is constructed to describe gregariousness of colonial insect larvae which occure in discrete natural habitat units. The model is based on the assumption that the distribution of individuals in a clump is determined by a balance between aggregative and dispersing movements of individuals. The model includes three parameters, i.e., clump size, carrying capacity of habitat units and intensity of aggregation against dispersal. The modes of effects of these parameters on the distribution of individuals are analyzed.

Several methods are developed to estimate these parameters from observed data, and their applicabilities are investigated. Application of these methods are described on the larval distribution of a colonial insect Pryeria sinicaMoore.
Relationship between female body size and demographic parameters in Bactrocera Malaysian A (Diptera: Tephritidae)
Authors: Chua Tock H.
Published: October 2006

The effect of body size, as measured by the head width, of the female Bactrocera sp. Malaysian A (kept separately in sexual pairs) on the demographic parameters was investigated in the laboratory under ambient conditions of 28–30°C, 78–85% RH and natural photoperiod. Body size was shown to influence significantly all the demographic parameters. The expectation of life of females at eclosion from pupae was respectively for head widths of 1.6, 1.8, 1.9, 2.0 and 2.1 mm: 76.2, 73.4, 73.8, 102.4 and 115.2 days. The mean number of eggs laid per female in its life time was respectively: 86.4±48.7, 181.8±56.1, 229.7±72.6, 364.3±69.4 and 477.5±109.3 which was significantly different from one another (F=3.73,P<0.05) especially the two smaller sizes from the two larger sizes. The regression line for total eggs laid (Y) against head width (X) was Y=785.2X−1208.7 (R2=0.35,P<0.001). The net reproductive rate (R0) was respectively 15.8, 34.0, 43.5, 66.9 and 88.8 eggs, while the intrinsic rate of increase (r) was respectivley 0.0435, 0.0538, 0.0670, 0.0665 and 0.0711. The results confirm that for mass rearing purposes, larger females which produce more offspring are to be preferred.
Spatial pattern indices based on distances between individuals on a line‐segment with finite length
Authors: Shiyomi Masae , Yamamura Kohji
Published: October 2006

Let us consider a strip‐wise habitat of line‐segment, like a corridor, to simplify the subject mathematically, and assume that the length of the habitat is γ and there are n individuals. Here, we assume that the spatial pattern of the individuals is random if the n distances from the left end of the habitat to each individual follow a uniform distribution on the strip. Under such an assumption, the variance of the distances between any two neighbors is represented by the formula nθ2(n+1)−2(n+2)−1 and the variance between n+1 distances between n individuals from the left end to the right end to the strip, is represented by the formula nθ2(n+1)−2(n+2)−1. These two kinds of variances can be used for determining (1) the spatial pattern of a population on the strip and (2) the spatial structure within the population, by comparison with the variances calculated from the data. Two examples cited from the literature, a cattle population on a pasture and an aphid population on a sycamore leaf, are presented.
Effects of interspecific competition on development and reproduction in two giant water bugs, Diplonychus japonicus vuillefroy and Diplonychus major esaki (Hemiptera: Belostomatidae)
Authors: Okada Hiroaki , Fujisaki Kenji , Nakasuji Fusao
Published: October 2006

We studied the interpecific competition between 2 species of predatory aquatic bugs, Diplonychus japonicus and D. major by conducting a field experiment. We set up 3 types of experimental plots in the paddy fields where D. major predominated. The two plots contained single species of either D. japonicus or D. major, respectively, and one plot had both species in equal number. We compared the development and the reproductive performance between plots in each species.

In D. japonicus, the number of eggs and early instar nymphs were significantly smaller in the plots containing both species than in the monospecific plots. However, the numbers of late instar nymphs and newly emerged adults were not significantly different between plots. The proportions of starved nymphs in both plots were larger than those in the D. japonicus's natural habitats. The final densities of adults in both plots were lower than those in the natural habitats. These results suggest that lower density of D. japonicus in these paddy fields is due to the lack of available food for nymphs rather than the effects of interspecific competition with D. major.

In D. major, significant differences were not found in the number of eggs, each instar nymphs and adults. These results suggest that the effects of interspecific competition did not affect the reproductive performance of D. major.
The evolution of dispersal polymorphisms in insects: The influence of habitats, host plants and mates
Authors: Denno Robert F.
Published: October 2006

Wing‐dimorphic, delphacid planthoppers were used to test hypotheses concerning the effects of habitat persistence and architectural complexity on the occurrence of dispersal. For reasons concerning both the durational stability of the habitat and the reduced availability of mates, selection has favored high levels of dispersal in species occupying temporary habitats. Flightlessness predominates in species occupying persistent habitats, and is promoted by a phenotypic trade‐off between reproductive success and flight capability. Wings are retained in tree‐inhabiting species, probably for reasons concerning the more effective negotiation of three‐dimensional habitats. In contrast, flightlessness is characteristic of those species inhabiting low profile host plants. For several delphacid genera, migratory species are larger than their sedentary congeners. Because body size and fecundity are positively related in planthoppers, the large body size observed in migratory taxa may result from selection for increased fecundity in colonizing species.
The physiological costs of flight capability in wing‐dimorphic crickets
Authors: Zera Anthony J. , Mole Simon
Published: October 2006

Nutritional indices, triglyceride levels and flight muscle developmental profiles were compared between long‐winged (LW) and short‐winged (SW; flightless) morphs of the crickets Gryllus rubens Scudder and G. firmus Scudder. This was done to identify potential physiological costs of flight capability in adults. The LW morph of each species converted a lower proportion of assimilated nutrients into biomass (reduced ECD) than did the SW morph. This documents increased respiratory metabolism in the LW morph. Triglyceride concentration was higher in LW vs. SW adults. This suggests that the elevated respiration in the LW morph may be at least partially due to the increased biosynthesis of this high energy substance. Preliminary data indicate higher respiration rates of LW functional vs. SW vestigial flight muscles. Collectively, these data suggest that the energetic cost of flight capability in adults results from biosynthesis of triglyceride flight fuel and flight muscle maintenance but not flight muscle growth. No flight muscle growth was observed in adults.
Insect migration: Variability and success in a capricious environment
Authors: Gatehouse A. G.
Published: October 2006

Stochastic effects of climate and weather have a pervasive influence on the induction, performance and evolution of migration. In wing‐dimorphic species, their influence on habitat quality, and on rates of development of the migrant itself, maintains variation in responses to environmental cues determining wing‐form and migratory behaviour. Migrants flying above their flight boundary layer rely on winds to disperse them across landscapes in which their habitats are distributed. Patterns of distribution of habitat patches, and the influence of changing windspeeds and direction on the displacements of migrants, result in selection for variation in migratory potential at each migration. In subsequent migrations, this variation and stochastic effects of the winds on groundtracks of individual migrants ensure that their destinations ‘sample’ the landscapes they travel over. The extent and resolution of this sampling, by which migrants reach favourable habitats, depend on the components of migratory potential, their mode of inheritance, and genetic correlations between them, as well as on the characteristics of the winds on which they travel.
Habitat fragmentation promotes fluctuating asymmetry but not morphological divergence in two geckos
Authors: Sarre Stephen
Published: October 2006

The process of species formation is often ignored in discussions on the conservation of biodiversity. Yet the clearance of vegetation may promote divergence among populations of a species through isolation, providing conditions for rapid genetic drift and novel selection pressures. Here, stepwise discriminant function analysis and fluctuating asymmetry are used to examine variation in morphology within and among non fragmented and recently fragmented populations of two species of gecko, Oedura reticulata and Gehyra variegata. High reclassification error rates using discriminant function analysis, indicate that fragmentation has had no detectable effect on morphological differentiation among populations of either species. In contrast, remnant populations of both species exhibit higher mean levels of fluctuating asymmetry than do populations in undisturbed habitat. For Oedura reticulata, levels of fluctuating asymmetry are negatively correlated with the log of adult population size. These results suggest that the changes following habitat clearance have been severe enough to cause increased developmental instability in populations of both species but not detectable morphological divergence. Given the high rate of extirpation of gecko populations in the study region and the extreme vulnerability of the remaining populations, it is unlikely that species formation will be significant in maintaining reptile diversity in that region.
Contest competition in Drosophila subobscura
Authors: Jones T. H. , Langefors Å. , Bonsall M. B. , Hassell M. P.
Published: October 2006

The role of larval intraspecific competition in laboratory populations of Drosophila subobscura was investigated. Mortality is density‐independent during the first 3 days after hatching but becomes density dependent as development proceeds to pupation. Although total biomass per patch was independent of initial egg density, competition between Drosophila larvae leads to the formation of smaller pupae. This resulted in a population that was dominated by suppressed individuals. Development rate of D. subobscura larvae was not affected by high larval densities. Smaller pupae give rise to females with fewer eggs in their ovarioles. A simple simulation model, predicting the effects of intraspecific competition on the fecundity of the next Drosophila generation is described.
Resolution of evolutionary conflict: a general theory and its applications
Authors: Higashi Masahiko , Yamamura Norio
Published: October 2006

While many cases in which conflict over the evolution of social behavior exists even between closely related individuals (e.g., parent‐offspring conflict) have been pointed out, little attention has been paid on the problem of where such conflict should lead. A general theory of conflict resolution, however, has recently been developed. The key idea of the theory is the incorporation of conflict costs in the inclusive fitness evaluation. The theory shows that if both sides engaged in the conflict can potentially control the other at a cost, the coevolutionary game of escalating the fight with increased conflict costs always leads either side to give in to the other, resolving the conflict. Here we examine the logical basis of the theory in terms of a simplest example, donor‐recipient conflict over the evolution of altruism, and to show its different types of application we review two more specific examples: reproductive‐worker conflict over true (sterile) worker evolution in termites and insider‐outsider conflict over group size determination. The latter exemplifies the resolution of conflict over the value of a variable (group size in this case) rather than a behavior, suggesting extended applicability of the basic theory.
Influences of wild crucifers on life history traits and flight ability of the diamondback moth, Plutella xylostella (Lepidoptera: Yponomeutidae)
Authors: Muhamad Omar , Tsukuda Ritsuko , Oki Yoko , Fujisaki Kenji , Nakasuji Fusao
Published: October 2006

The larvae of Plutella xylostella were fed on five wild crucifers, Capsella bursa‐pastoris, Lepidium virginicum, Cardamine flexuosa, Rorippa indica, R. islandica and a crop, cabbage. The developmental period of the immature stages, adult longevity, preoviposition period, fecundity and morphometrical characters of the adults were measured. The flight activity of the adults was also measured by the tethered flight method. All the wild plants except for R. islandica were less suitable host plants than cabbage, and larvae which were fed on these less suitable plants emerged as smaller adults with shorter wings. The smaller female adults had lower fecundity but a higher flight activity. Smaller adults measured in terms of their pupal weight among individuals fed on the same host plant had longer wings. These smaller adults with longer wing flew more actively.
Simultaneous estimation of mortality and dispersal rates of an artificially released population
Authors: Matsuda Hiroyuki , Akamine Tatsuro
Published: October 2006

Mark‐recapture methods cannot estimate both mortality and dispersal rates of a wild population simultaneously. However, when an artificially cultured population is released into an area, the initial population size and the initial population distribution are usually known. If artificially cultured individuals are released with marks or distinguished from wild individuals or if no wild individual exists in the study area, we can estimate both the mortality and dispersal rates of the artificial population. The numbers of dispersed and dead individuals are estimated from the dispersal rate from the diffusion model and the total decreasing rate estimated from a mark‐recapture data. We can estimate both the time‐dependent and time‐independent dispersal rates from the data. We choose the best fit model that has the smallest value of Akaike's Information Criteria. We also consider ‘concentric circles approximation” of spatial distribution, in which the cumulative and frequency distributions are analytically obtained.
Dynamics of Sitotroga cerealella (olivier) (lepidoptera: gelechiidae) and Sitophilus zeamais motschulsky (Coleoptera: Curculionidae) populations in a small bulk of stored corn
Authors: Arbogast Richard T. , Mullen Michael A.
Published: October 2006

The dynamics of Angoumois grain moth, Sitotroga cerealella (Olivier), and maize weevil, Sitophilus zeamaisMotschulsky, populations breeding in a small bulk (initially 5.36 t) of shelled corn were studied over an 8‐year period by monthly sampling. The weevil population showed wide fluctuations in density superimposed on a general decline with time. The moth population showed no upward or downward trend for the first 60 months, although it fluctuated widely. Following a decline that occurred between 56 and 60 months, the moth population fluctuated within a much narrower range, and there was a general decrease in density with time. The decline of the weevil population paralleled deterioration of the corn as did that of the moth population after ca 60 months, and the decline of both species probably resulted from increasing scarcity of suitable breeding sites. Both populations exhibited seasonal variation in density with minima in late summer and early fall, following periods of adversely high temperatures in the storage shed. The populations increased during the fall, leveled off or declined slightly during the winter months, and then increased to maximum levels in late spring or early summer. It thus appears that high temperatures had a greater adverse effect on the populations than low temperatures. The grain moth and the maize weevil both tended to be randomly dispersed at low population levels and moderately aggregated at intermediate and high levels, although the degree of aggregation was not correlated with population density when low population levels were considered separately, and the maize weevil showed a greater tendency for aggregation than did the grain moth. Analysis of individual samples at fixed points in time showed a conspicuous bias for negative correlation between numbers of the two species within sampling quadrats, suggesting a tendency for the two species to segregate within the grain mass. This process could have resulted from behavioral differences or from the destruction of one species by the other. Competitive displacement of the grain moth by the maize weevil has been demonstrated in laboratory experiments but has rarely been observed under natural conditions, and in our study the two species coexisted for 8 years in a relatively small grain bulk.
The feeding from edge towards inner part in soybean plot in rufous turtle dove, Streptopellia orientalis (Latham) and the estimation of passing rate of the flock
Authors: Nakamura Kazuo , Matsuoka Shigeru
Published: October 2006

Rufous turtle dove, Streptopelia orientalis, coming to the soybean field entered it from the outer part to eat soybean cotyledons. As a result, the injured plants extended from the outer to inner parts in the field. A model expressing these behaviours was constructed here, by assuming that the amount of food birds can eat in one block determines whether they stay there or move into neighbour block. As the food decrease due to exploitation of them by birds, birds enter into farther parts with the passage of time.

The rate of feeding in all visiting birds (an0 where a is the rate of feeding per individual and n0 the number of birds visiting) and the rate of staying at a block, b, was estimated from the field experimental results, using the above model. The value of an0 fluctuated greatly, depending upon the season in which soybean seeds sowed. The value of b also fluctuated inversely with that of an0, suggesting the the staying rate decreases with an increase in the number of doves coming, probably because of interference among individuals.
A preliminary study on quantitative relations among growth, reproduction and mortality in fishes
Authors: Kitahara Takeru , Hiyama Yoshiaki , Tokai Tadashi
Published: October 2006

As a quantitative approach to the life histories of fishes, the present paper attempted to predict a relation among reproduction, growth and mortality numerically with a technique of control theory, the discrete maximum principle. A method for predicting the relation was derived on the postulate that natural selection maximized the net reproductive rate subject to a few constraints. The derived method was applied to Atlantic cod and Atlantic herring populations in the Southern Gulf of St. Lawrence as numerical examples. The examples demonstrated that the theoretical reproductive effort and body weight were well consistent with the observed ones every age but the theoretical survival rates were slightly different from the observed ones. For the reasons mentioned below, however, it should be interpreted that the examples rather support the adopted postulate to a certain degree. First, in general, it is very difficult to obtain good estimates of the rates with traditional methods. Second, intense fishing pressure possibly changes the life history parameters to some extent in fish populations. Moreover, the examples also suggested that, to examine the postulate in further detail, similar analyses had to be made with the data of many fish populations on which intense fishing pressure had not been exerted.
Space partitioning among the wolf spider Pardosa amentata species group in Hokkaido, Japan
Authors: Suwa Masayoshi
Published: October 2006

There are 4 species belonging to the wolf spider Pardosa amentata species group in Hokkaido. The 4 species have separately occurred in Hokkaido in general, but a few species have sometimes occurred together at the same sites. Their biology at the coexisting sites, with special reference to partitioning of space was studied. P. agraria mainly inhabited fields and occurred widely in Hokkaido. P. hokkaido, P. brebivulva and P. lugubris inhabited the vicinity of forests and occurred in southern Hokkaido and on the side of the Sea of Japan in Hokkaido, all over Hokkaido excent the side of the Sea of Japan in central Hokkaido, and the lowlands and highlands in northern and eastern Hokkaido and mainly the highlands in other regions, respectively. In eastern Hokkaido where P. brevivulva and P. lugubris have coexisted, as the number of spiders detected and the number of localities of the former were less than those of the latter, it was concluded that the former occurred mainly in southern Hokkaido and the Hidaka region. In southern Hokkaido where P. hokkaido and P. brevivulva have coexisted, few individuals of both species were collected together at the same sites, and they were distributed allotopically. In short, the partitioning of space among the P. amentata species group occurring in Hokkaido was clear. From investigations on the coexisting sites and some other reports, it was considered that food, life cycle and diel activity periodicity among Pardosa occurring in Hokkaido were similar to one another. This may be one of the causes of the clear space partitioning among Pardosa. Since Pardosa is a raptorial predator that does not weave but wanders on the ground and uses space horizontally, available prey resource for Pardosa would be limited. It was therefore conjectured that the spider would be prone to space segregation, even if the spider could segregate the other niche dimensions. The partitioning of space between P. agraria and P. hokkaido inhabiting distinct habitats was loose when it was compared with that between species inhabiting similar habitats. As most of the spiders observed in the overlapping areas were females with egg cocoons, which required little food, the reduced feeding was considered to have allowed the loose partitioning.
Time‐specific life tables for the pea aphid, Acyrthosiphon pisum (Harris), on alfalfa
Authors: Hutchison William D. , Hogg David B.
Published: October 2006

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 (rm) 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 of A. 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 densities A. pisum populations increased exponentially.
Population regulation of the euonymus gall midge Masakimyia pustulaeYukawa andSunose (Diptera: Cecidomyiidae) by hymenopterous parasitoids
Authors: Sunose Tsukasa
Published: October 2006

Yearly population fluctuations of M. pustulae were investigated at 19 sites in Kyushu. In sites where a platygastrid is the only parasitoid of the midge, the percentage parasitism was very low in the incipient stage of the outbreak of the midge populations. After the number of midges reached a peak, the midge populations declined as the percentage parasitism increased, and then the outbreak ceased. On the other hand, in several populations no outbreak was found and the percentage parasitism was constantly at a high level. Therefore, the immediate cause for the outbreak seemed to be a decline of the percentage parasitism. Like the midge, the platygastrid has one generation each year, and its females also emerge in spring to deposit their eggs within host eggs. The decline of the percentage parasitism seemed to be mainly affected by the time lag between emergence periods of M. pustulae and the platygastrid.

In the midge populations parasitized by both the platygastrid and a eulophid (Chrysonotomyia sp.), an extinction of the population was observed, resulting from parasitism by the latter, Chrysonotomyia sp. is polyphagous and multivoltine, and is a late parasitoid, as discussed byAskew (1975). When the density of the midges is very low, the platygastrid may leave the host eggs unparasitized, while Chrysonotomyia sp. may not, because the mature galls are conspicuous.
Polygyny and the breeding success of the great reed warbler Acrocephalus arundinaceus
Authors: Urano Eiichiro
Published: October 2006

Settlement date, mating status, and breeding success of individually marked great reed warblers, Acrocephalus arundinaceus, were studied during the 1980–84 breeding seasons in Kahokugata, Ishikawa Prefecture, Japan. Twenty‐five per cent of the territorial males were polygynous, of which the majority were bigamous. The settling periods of both sexes were long, extending for 65 days in males and 49 days in females. About 80% of males and females settled in the first half of the settling period, and the settlement date of 28–54% males overlapped with that of females. Many of the late settlers were bachelors and the males which mated earlier tended to be polygynous. The timing of a male's settlement is important in acquiring mates. Fifty‐five per cent of eggs laid were lost before fledging, mainly due to predation. The mean number of fledglings was 3.19 per primary female, 2.41 per secondary female, and 2.80 per monogamous female. Comparison of the number of fledglings of females which mated during the same period showed that the presence of another female in the same territory did not adversely affect the breeding success of either of the polygynous females. Polygynous males have the advantage of decreasing the risk of breeding failure under high predation pressure.
Population biology of the broad‐horned flour beetle, Gnathocerus cornutus (F.) II. Crowding effects of larvae on their survival and development
Authors: Tsuda Yoshio , Yoshida Toshiharu
Published: October 2006

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 that G. 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 on Tribolium confusumJacqueline duVal.
Conspecific host discrimination by ovipositing Euphydryas editha butterflies: Its nature and its consequences for offspring survivorship
Authors: Mackay Duncan A.
Published: October 2006

Ovipositing E. editha butterflies display post‐alighting discrimination among patches of Collinsia torreyi, one of their major hosts in the General's Highway (GH) population at a montane site in California. Females tended to accept (i.e. oviposit on) dense patches of this host and to reject sparse patches. Possible behavioural mechanisms underlying this tendency are discussed. The consequences of this non‐random pattern of oviposition for egg and larval survivorship were investigated and no differences were found in the survivorship of larvae on acceptable and unacceptable collinsias.
Ecological significance of the wing polymorphism of the oriental chinch bug, Cavelerius saccharivorusOkajima (Heteroptera: Lygaeidae)
Authors: Fujisaki Kenji
Published: October 2006

The wing polymorphism of the oriental chinch bug, Cavelerius saccharivorus, was studied in relation to its reproductive strategy. The frequency distribution of wing form in terms of the relative wing length (R.W.L.) changed with increase in the population density from a single modality biased toward the brachypterous form to bimodality with both macropterous and more extreme brachypterous forms. Since some evidences in the field showed that fliers are limited to macropters, such a bimodality of wing form indicated that C. saccharivorus employs a mixed strategy with some portion of adults staying on in the same habitat, whereas the rest disperse. Moreover, macropters were larger in body size than brachypters emerging in high density populations, although smaller than brachypters emerging in low density populations. Larger body size as well as the delay of ovarian maturation in macropters was considered to be a beneficial trait for migratory behaviour.
Resource utilization pattern of two species of tetranychid mites (Acarina: Tetranychidae)
Authors: Kondo Akira , Takafuji Akio
Published: October 2006

Life history and resource utilization pattern were compared between two closely related mite species of the genus Tetranychus.

Tetranychus urticae developed more quickly and had a higher oviposition rate than T. kanzawai. Consequently, the potential for population increase was greater for T. urticae than for T. kanzawai but the difference was slight.

T. urticae was more tolerant of a deteriorating food resource and/or over‐crowding. T. kanzawai responded more sensitively to food deterioration and dispersed more quickly.

There was a considerable difference between injury patterns by the two species. T. kanzawai damaged host plants more severely, causing earlier and more extensive defoliation of the plants.

The maximum population size achieved by T. urticae was 2 to 3 times greater than that of T. kanzawai on potted host plant. This showed that the former could utilize a food resource much more efficiently.
Pheromone trapping models for pest control: Effects of mating patterns and immigration
Authors: Barclay Hugh J.
Published: October 2006

Several models are presented which examine pest population behaviour with the release of female sex pheromones for the attraction and annihilation of males. These models include male polygamy and female monogamy, various mating frequencies, delayed mating of females, immigration of one or all individual types, and differential survivorship of males and females.

In all the models there are two steady states, a stable s.s. at the origin and an unstable s.s. in the positive domain for a given value of pheromone release rate. In all the models, control relies on the reduced ability of males to fertilize virgin females following trapping and male annihilation. As such, control is very sensitive to mating frequency, being very difficult when males mate frequently. Control is also very difficult with the immigration of even a moderate number of fertilized females. Control is much easier when mating is delayed, especially if survivorship is low, or with density dependent population regulation.
Component analysis and modelling of the movement process: The simulation of simple tracks
Authors: Zalucki M. P. , Kitching R. L.
Published: October 2006

A model for the simulation of simple snail tracks is presented. The parameters required by the model include: (1) the distribution of turn angles at each step; (2) the mean and (3) the variance of step sizes; (4) the initial bearing angle and (5) the proportion of time spent moving. The model readily generates realistic tracks and predicts adequately values of parameters not specifically built into the model. If observations on the above five parameters are collected at the correct scale, then we suggest the model represents a general, canonical description of movement. The notion of what constitutes correctness is discussed.
Differences in egg wastage by superparasitism, contrasting Venturia (=Nemeritis) canescens searching singly versus searching in groups
Authors: Huffaker C. B. , Matsumoto B. M.
Published: October 2006

A statistical and graphic study is presented of the wastage of eggs by Venturia (=Nemeritis) canescens when searching singly and in groups of 10 among hosts at four different host densities in laboratory universes as described byHuffaker andMatsumoto (preceding paper of this journal). The host insect was the fluour moth Anagasta kühniella and the host densities used were 10, 30, 100 and 200 per universe. Intensity of egg wastage due to superparasitim varied significantly according to host density, and between the two parasite densities employed, 1 and 10, using both F‐tests and chi‐square tests. Plots of k‐factor analysis on this egg wastage showed high negative correlations with host density, and the raw data for single parasites was well represented by a parabola while that for the grouped parasites departed from this relationship only at the lowest host density.
Prey capture tactics of spiders: An analysis based on a simulation model for spider's growth
Authors: Nakamura Kazuo
Published: October 2006

The prey capture tactics of spiders was analyzed, considering the energy gained by the capture of prey and that required for it. For the purpose of it, a growth model of spiders was constructed, expressing the flow rate of prey biomass to the spider's body by differential equations. Solving these equations under the differing values of three parameters, growth curves of spiders was obtained. These three parameters are the amount of prey biomass supplied daily to spiders, x0, the rate of prey capture of spiders, α, and a coefficient of the respiration rate required for the capture of prey, k. When the value of k increased, spiders could grow only at high value of x0. These results suggest that habitats with small prey biomass are preferred by spiders adopting a sit‐and‐wait tactics for prey capture, which requires small values of k. Wolf spiders are one of these spiders showing that tactics. On the other hand, web‐builders which require large amount of energy for spinning webs (namely, take large value of k), are able to grow only in the habitats with large prey biomass. Each species of spiders are considered to locate in a certain point between both extremes of these tactics for the capture of prey.
Stabilization of the population of a parasite on fruit by the population of a cleptoparasite
Authors: Yamamura Norio , Iwahashi Osamu
Published: October 2006

When there exist two species such that one is a parasite on fruit and the other exploits the parasitized fruits, they must compete for a limited resource with each other. The relation between Dacus cucurbitae and Atherigona orientalis is an example of such a situation. We raise a question whether the population of a parasite on fruit can be stabilized by the existence of the cleptoparasite of the parasite on fruit.

The changes in their population densities are represented as a differential equation with time delayed parameters, which is deduced from the context of life histories of the two species. An index representing degree of overlapping of generations (g) is defined as an average oviposition period devided by the average preoviposition period, and the value is assumed to be the same in the two species.

The stability of the system is classified by three parameters: the reproductive rate of the parasite on fruits (R), the survival probability of it through competition against the cleptoparasite (p), and the generation overlapping index (g).

For small values of g, e.g. less than some 0.5, the stability is determined mainly by a product of Rp: the values larger than 1 result in no equilibrium and infinite increase of both species, the values near 0 lead to large amplitude oscillations, and the intermediate values make stable equilibria or regular small oscillations. As g takes the larger values, the stability region in the space (p, R) occupies the larger area.

The model presented here is well adjusted to the fluctuating pattern of the population of D. cucurbitae on Okinawa Is., and would also be applied to analysis of both hyperparasitisms and inquilin.
Decrease in respiratory rate in a wolf spider, Pardosa astrigera (L. Koch), under starvation
Authors: Tanaka Koichi , Itô Yosiaki
Published: October 2006

Effects of starvation on the suryival period and the respiratory rate in adults of a wolf spider, Pardosa astrigera (L. Koch), were investigated. The spiders used were divided into four groups: well‐fed, starved and two limited food groups; in the latter two, each spider was supplied with one leafhopper every second or third day. Adult males and females of P. astrigera could survive for a long time; 28.8±2.7 days and 54.4±18.9 days, respectively, without any food. The longevities shown here were 73.8% for males and 78.6% for females of those of well‐fed spiders, indicating that P. astrigera adults have a strong tolerance to starvation. The respiratory rate of well‐fed adults showed no tendency to increase or decrease with their aging; the mean respiratory rates were 4.86×10−4 mg CO2/mg f.w. (fresh body weight)/hr for males and 3.80×10−4 mg CO2/mg f.w./hr for females. The respiratory rates of starved spiders increased during the first two days of starvation but decreased markedly from the third to the twelfth day, and thereafter retained an almost constant level for each sex. The mean respiratory rates after the twelfth day of starvation were 2.49×10−4 mg CO2/mg f.w./hr for males and 2.76×10−4 mg CO2/mg f.w./hr for females; these values were respectively 48.4% and 63.0% of those prior to starvation. The fresh body weight of starved spiders decreased linearly with time but the rate was small. The respiratory rates of the limited food groups tended to decline with time and thereby their weight losses were minimized. The decrease in the respiratory rate under starvation was considered not to be due to spider exhaustion or senescence but due to an intrinsic change in behaviour and/or metabolism, because when the spiders were supplied with ample food for five days after starvation, the respiratory rate and the body weight rapidly recovered to near the levels prior to starvation. It is suggested that starved spiders use a higher ratio of fat as catabolic substrate than normally fed or satiated ones. Feeding strategies of poikilo‐therm predators are discussed.