Der zusammenfassenden Arbeit der Oribatidenzonosen in Bezug auf die Pflanzendecken und Bodencharaktere vorgehend, wurden hier vor allem die Oribatidenzonosen selbst horizontalerweise analysiert. Mehrere Charakteristika fur Analyse der Tiergemeinschaften wurden unter allen 18 Bestanden vergleichen, wobei der Verfasser einige neue Begriffe hineinbrachte. Sie sind Artenzahl, Grossengruppen, Abundanz, Biodeckung, Dominanz, JACCARDsche Zahl, RENKONENsche Zahl, Grossengruppenidentitat usw. und man kann die untersuchten Bestande je nach ihrem Charakteristikum verschiedenartig gruppieren.
The value computing from the following formula was proposed as a new biotic index based on the species number of Bacillariophyceae, to the water pollution by organic matters in a stream. The formula is : [numerical formula] where A is the number of the intolerant species and varieties, B is that of the indifferent species, and C is that of the exclusively pollutional species. Table 2 indicates the values of A, B, C and the biotic index in each sampling station of the Tokoro River in Hokkaido. The degrees of water pollution at the seven sampling stations are discussed based on the values of the biotic index given in Table 2.
In this paper the writer describes the results of observations on the phase variation in the larval characters of the cabbage armyworm, Mamestra (Barathra) brassicae, under different conditions of rearing density and temperature. The materials used for the experiments were offsprings of non-diapausing individuals of the first brood of the Noheji strain (Aomori Pref.) Details of experimental design are given in Table 1. The larvae were fed on young leaves of the goose foot, Chenopodium centrorubrum MAKINO, one of the wild plants. High mortality was encountered at the final larval stage in crowded cultures and this tendency was intensified at 28℃ (Fig. 1). As shown in Fig. 2,temperature influences the skin color of the final instar larvae, the highest percentage of dark colored larvae was obtained at 20〜22℃ and the lowest one at 28℃. Furthermore, the larval coloration was affected by rearing density and the percentage of dark colored larvae in a culture increased with the increase of density (Figs. 2 and 3). Crowding induces rapid development at 25 and 28℃ and slow development at 20〜22℃ (Table 2), and produces lighter female purae at each temperature employed in the experiment (Table 3). Fig.44 indicates that the larvae in crowded cultures grew at the same rate as those in solitary cultures both at 25 and 28℃ and that there was a difference in the rate tf growth between density cultures at 20〜22℃.
sampling design for estimating the population density of successive states is discussed from analysis of the data which were obtained every other day as the entire distribution maps of the insect. Censuses were conducted in the two plots, each containing 500 rice plants, that were arranged in the paddy field of late planting rice. Analysis of the data was made along two lines. First, by the method which was proposed by BEALL (1939), and the effect of stratification of the plot, relative efficiency of various sampling units, and sampling size required for securing a given degree of accuracy were examined. As regards stratification, there was no detectable improvement in raising the sampling efficiency. Sampling unit type III' which was taken parallel to the direction of columns was somewhat more excellent in relative efficiency than the other types for the stage egg to the first instar, while for the second instar sampling unit type III which is equal in size out differs in from with type III showed more excellency. For less the third instar sampling unit type I with minimum unit size (one stump of rice plant) revealed stable excellency. Sampling size to secure a given degree of accuracy, e.g. α=0.20,using the most effective sampling unit, is 33〜50 per cent of the slot for the stage egg to the third instar, but 15〜20 per cent is enough for less the fourth instar. Secondly, using random numbers, samples with different sample size were drwwn from the distribution maps for each stage of the insect and sampling variation of estimates was examined. From this procedure there can be detected that C.V. of the estimates of population mean becomes small and stable not less than 40 per cent sampling for the stages egg to the second instar, not less than 20 per cent and 10 per cent for the stages of the third and the fourth instar, respectively. These results were elucidated from the viewpoints of behaviour of the insect relative to egg laying and dispersal. Sampling design-field plot lay out and determination of census date- was recommended for the estimation of Nezara population. Determination of the census date for each developmental stage can be made by using the incidence curve of the eggs and the average developmental period of each stage.
The larval duration, the emerging percentage, and the weight of Drosophila melanogaster, emerged from the "live yeast medium" or A-medium containing few live yeast and those from the "dead yeast medium." or B-medium containing sufficient dead yeast were compared. (1) The larval duration was not elongated so much when the larval density increased. There was no apparent difference in the larval duration between the A- and B-medium. (2) The emerging percentage began to decrease in the A-medium when the larval density exceeded 20 larvae per vial, then it decreased to near 0 per cent at high larval density. In the B-medium, the emerging percentage did not decrease remarkably at high larval density. (3) The weight of flies began to decrease when the density exceeded 10 larvae per vial, then it kept a nearly constant value at densities higher than 30 larvae per vial in the A-medium. In the case of B-medium the weight did not decrease when the density increased. (4) The action of the shortage of food first takes its effects upon the individual level that is the decrease of the fly's weight, then it appears on the population level that is the decrease of the emerging percentage. (5) The total weight of flies was at the maximum at the density of 20 larvae per vial in the A-medium. In the case of B-medium the total weight of flies increased with advancing densities.