The author carried out three experiments under field and laboratory conditions to evaluate the role of intraspecific regulatory machanisms in the population dynamics of the 28-spotted lady beetle. Experiments were started by introducing the adults at different densitiesinto the field cages. With increasing parental density, the number of eggs laid per female decreased and the percentage of eggs eaten by adult beetles (egg cannibalism) increased, and in consequence of these processes, egg mortality became higher. During the larval stage the mortality was mainly due to food shortage. The number of progeny produced per female was decreased in a density dependent manner. A graphical key factor analysis proposed by VARLEY and GRADWELL revealed that the density dependent regulation mechanisms scting in the adult stage, viz, the reduction in fecundity and egg cannibalism, were the key factors govering the variation in total survival in these experiments.
The purpose of this paper is to define the critical time necessary for the occurrence of social facilitation in feeding behavior during an early feeding period of the himedaka, Oryzias latipes. In the three experimental conditions when the number of stimulating fish was 0,1 or 3,the feeding behavior of the reacting fish was observed directly and continuously for 10 minutes from the time of introduction of the bait, Daphnia pulex. The social facilitation which depends on the presence recognition effect' of the companion as a stimulus was recognized all through the observational period. Several considerations on the concave variation in the social facilitation ratio (F. R.) are described.
Injury to plants due to air pollution is found in the areas adjacent to such chemical factories as alminium refineries due to the gaseous fluoride compounds generated. The authors observed the gradual discoloration of Moso-chiku (Phyllostachys pubescens) leaves from tip to base in accordance with the degree of injury in the area adjacent to an aluminium refinery in Ehime Pref. The fluoride contents of the leaves were also determined. It was found that the closer to the factory, the more remarkable the discoloration of the leaves. The discoloration of Moso-chiku leaves was correlated to the fluoride contents of the leaves. The areal distribution of discolored Moso-chiku leaves showed the range of fluoride air pollution affecting the growth of the plant. For this reason, Mosochiku is useful as an indicator plant of air pollution by fluoride.
The response of predator population to the density and the spatial distribution of prey population (numerical response) in their natural habitat was studied by using a predatory coccinellid, Aiolocaria hexaspilota HOPE and its prey, the walnut leaf beetle, Gastrolina depressa BALY. Analyses of life tables and spatial distributions of both A. hexaspilota and G. depressa indicated the existence of a tight interaction between the two species. Namely, the main mortality factor in all the stages except adult of G. depressa was the predation by larvae and adults of A. hexaspilota, and that of A. hexaspilota larvae was dispersal and/or cannibalism caused by shortage of prey. Although the absolute amount of prey in the whole research area was sufficient to support the existing larval population of A. hexaspilota, there actually were a number of trees on which A. hexaspilota larvae became extinct due to food shortage. As the reason for this it was suggested that A. hexaspllota adults laid eggs in some trees excessively, and the larvae could not move among trees efficiently enough to compensate for such an inadequate response by the adults to the prey distribution.
Annual water balance at 148 localities in the Korean Peninsula was calculated according to THORNTHWAITE'S method to obtain estimates of annual water surplus and deficiency and of the moisture index. Water deficiency from 10 mm/yr to 111 mm/yr occured only at 10 stations, whereas 141 stations showed water surplus ranging from 4 mm/yr to 997 mm/yr. Three climatic provinces, perhumid, humid and semiarid, were distinguished based on the distribution of THORNTHWAITE'S moisture index and KIRA'S humidity/aridity index. These two indices proved to be closely and linearly correlated with each other as far as this region was concerned.
Studies were made on the relationship between respiration rate and nitrogen concentration of trees (mainly Plnus densiflora), in the correlations found in various organs (i.e. needle, branch, stem) and the seasonal variations. The respiration rate differed greatly between the photosynthetic and nonphotosynthetic organs. However, when the respiration rate of these organs was comnared on a unit nitrogen concentration basis, the difference was smaller. That is, the respiration tended to increase with higher nitrogen content. The same relation existed in differnt kinds of tree leaves. The respiration rates of current needles and branches, calculated at 20℃, showed the minimum values in summer and the maximum in winter, and those of 1-year-old needles and branches showed smaller seasonal variations. The seasonal variations in nitrogen concentration showed a concave trend in common with respiration rates.