In a preceding paper, it was reported that the activity of shell movement and the amount of feces in the Japanese pearl oysters, Pteria (Pinctada) martensii (DUNKER) were lowered by the presence of fouling organisms. This study has been carried out on the harmful influence of fouling organisms upon the regeneration of shell margin and the byssus secretion of the bivalve with a view to making clear whether shell cleaning is effective for increasing the growth of the bivalve and the quality of pearls. The results obtained are summarized as follows : 1. The activity of pearl oysters which regenerate the eliminated part of the shell margin notably increases just after the cleaning work of the shell, and afterwards it gradually falls with an increase of fouling organisms. Such a recovery as found above on the activity of shell growth changes by the degree of the ill-effect of fouling organisms in fouled pearl oysters. 2. The secretion activity of byssus in fouled pearl oysters changes by cleaning the shell ; the number of byssus secreted during 24 hours in the cleaned pearl oysters was doubled for about 5 days after shell cleaning. It seems that the activity of byssus secretion, in this case, was relatively slow in recovery. 3. The results mentioned above together with the outcome of the preceding paper suggests that the activity of the pearl oysters is harmfully influenced by the presence of fouling organisms, and the work of shell cleaning is effective for the production of pearls.
Difference in the density effect between the two wing-forms, brachypterous and macropterous adults of the brown planthopper, Nilaparvata lugens STAL were studied. 1. The number of eggs per individual was affected both in brachypterous and macropterous forms by the difference of population densities, As density in test tube became high, the number of eggs deposited decreased in the macropterous form more than in the brachypterous form. 2. Average pre-oviposition periods in the two forms decreased as the density became high. The trend of decrease of in the brachypterous form did not appear in low density such as 1 or 2 pairs in the test tube. 3. Longevity of the macropterous form became short toward high density, contrary to that of the brachypterous form. 4. Distribution of two wing-forms on the rice seedlings was affected by density. As density became high, the macropterous form was distributed on the higher parts of the rice seedling or of the inner wall of the test tube and moved more actively. Brachypterous form more or less tended to be distributed throughout rice seedling. As density became high, it rather moved less actively. Those analyses of density effects showed that the interaction of the individuals was more important than space for solving the mechanism of density of the adults of brown planthopper.
1. There were two local roosting flocks in the Zenkoji basin in winter, that is to say, in the Akaiwa and Sakaki areas. During both the non-snow season from December 23 to 30 1963 and the snow seasson from January 11 to 31,1964,we observed about 43,000-50,000 Gray Starlings in the former area, and about 1,300-220 in the latter. 2. In the Akaiwa local roosting flock, a large flock assembled with a tendency of group formation, but at the marginal parts of this area, only a few assembled to make some smaller winter roosts with the adults remaining at their nesting site. In the Sakaki local roosting flock, the lay of the land is complicate and thus they formed smaller area roosts. But we may say these smaller winter roosts belong to the Ueda local roosting flock. 3. The apple orchards are their important feeding places in winter. Their flight line was along the apple orchards, which were abundant in the northern parts of the Zenkoji basin ; They made their main roost in it. So we may be able to presume some relations between the population density of the Gray Starling and the distribution of the apple orchards.
Based upon the necessity for a biocoenotic approach to wild bee studies, the relative abundance of andrenid bees in Sapporo was surveyed by periodical sampling on flowers, in two areas and for two years. Among the 20 species captured (1,709 individuals), Andrena hebes and A. esoensis are regarded as stable dominant species common to the two areas. Andrena benefica, A. watasei, A. sublevigats and A. valeriana are also dominant, but either only in one area or only for one year. Interesting differences in the composition of the andrenid assemblage between the two areas, located near one another, and between 1959 and 1965,are described and discussed. The phenology shows a definite succession, divided into the spring phase with numerous species visiting various flowers and the rather monotonous summer phase with two oligotrophic species, A. esoensis and A. valeriana as dominants. The specific difference in flower preference was given together with the difference between the two areas. Most specimens were captured from a limited number of flower species, among which the introduced species, European dandelion, rape and willows (partly) and native species, Gagea Lutea, Petasites japonicus and willows (partly), are important for spring species, while legumes, especially white clover, are the predominantly visited flowers in summer.
Anstatt des Gestrauches von Zwergkiefern, das sich oberhalb der Waldgrenze weit entwickelt, befinden sich alpine Heiden und Schutthaldewiesen im Japanischen Sudalpen, wo der Windstoβ zu stark wirkt und es sich zu spat ausapert. Das Saussureo-Potentilletum matsumurae ist eine neue alpinen Heidegesellschaft als Verbindung von Hemikryptophyten und kriechenden Chamaephyten. Seine Subassoziation, oxytropetosum ist die Zwischengesellschaft, die den typischen Teil zum Arctoo-Cetrarietum verbindet. Das Hedysaro-Astragaletum membranaceae kommt auf mehr oder weniger stabillierten steilen Schutthalden oder Felsen vor. Die zwei Assoziationen lassen sich in einem neuen Verband Hedysarion umfassen, das sich vom Arcterion nanae sowohl floristisch wie auch okologisch unterscheidet. Theoretisch existieren die Trockenserie von der Gyrophora-Rhizocarpon-Flechtengesellschaft auf Felsen, durch die Minuartia arctica-Potentilla matsumurae-Gesellschaft auf den Schutthalden, das Arctoo-Cetrarietum crispae und das Vaccinio-Pinetum pumilae cetrarietosum zum rubetosum pedati und die Hygloserie vom Minuartia-Potentilla-Schutthalde durch das Hedysaro-Astragaletum zum Ranunculo-Trollietum, aber wirklich bleiben sie alle in Dauergesellschaften.