Kazuo Nakamura

The ingestion in wolf spiders II. The expression of degree of hunger and amount of ingestion in relation to spider's hunger

To express the degree of hunger during both of feeding and unfeeding periods of spiders, equations for the amount of ingestion and food disappearance from the gut were presented using three components: capacity of gut, rate of ingestion and rate of food disappearance. The degree of hunger was expressed by the rate of unfilled capacity of gut to the capacity of gut based on these equations. The rates of ingestion and food disappearance were estimated from the results of experiment with a wolf spider,Pardosa laura. The equations obtained well applied to the experimental result. By changing values of these rates, it was revealed that the ratio of rates of ingestion to food disappearance determine the amount of ingestion.

Population dynamics of the chestnut gall-wasp,Dryocosmus kuriphilus Yasumatsu (Hymenoptera: Cynipidae)

SummaryDuring the course of a 10-year investigation on the population dynamics of Dryocosmus kuriphilus, a rapid decrease in the number of individuals was noticed in the adult stage. To detect the role of predation by spiders in causing this high adult mortality, spiders collected from the survey station were tested for their reaction to Drycosmus antiserum. About 20∼50% of the spiders collected during the emergence period of D. kuriphilus reacted positively, showing that the species of Thomisidae, Argiopidae, Agelenidae and Salticidae were the important predators. The predation ratio for the total adult wasp population was estimated at 8.1% in 1968, 20.2% in 1969 and much higher in 1970, increasing with decreasing population density of the wasps. However, the predation by spiders could not account for all of the adult mortality of D. kuriphilus.

A model of the functional response of a predator to prey density involving the hunger effect

SummaryA mathematical model of the functional response to prey density involving the hunger effect was constructed in this paper. In that model, the amount of prey captured by predators, y, is assumed to be proportional to the product of the prey density, x, and the degree of hunger. The range of prey density is divided into the following three areas along the x-axis, according to the maximum rate of ingestion and the maximum rate of capture: (i) the area in which the value of y increases convexly with increasing x, (ii) the area in which the value of y increases proportionally to x and (iii) the area in which y reaches the maximum.It is shown that these equations are a generalization of Ivlevs equation, and Hollings disc epuation, that is, both equations hold in special cases in only the first area of x.These equations were applied to several experimental results obtained by using two kinds of wolf spiders and some values of parameters were estimated.

Population dynamics of the chestnut gall-wasp,Dryocosmus kuriphilus Yasumatsu (Hymenoptera: Cynipidae): II. Distribution of individuals in bud of chestnut tree

As a part of serial study on population dynamics of the chestnut gall-wasp,Dryocosmus kuriphilus, analyses of the distribution of eggs, gall-cells and emergent holes were made from the statistical point of view. Many of distributions of the eggs per bud could be described by the truncated Poisson, but some cases showed slight overdispersion than expected by chance. Because of no linear increase of

Estimation of population productivity of Parapleurus alliaceus Germar (Orthoptera: Acridiidae) on a Miscanthus sinensis Anders. grassland

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The ingestion in wolf spiders I. Capacity of gut ofLycosa pseudoannulata

with increasing

Fluctuations of grasshopper populations on aMiscanthus sinensis grassland

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