To obtain ecological and phytosociological informations on the grassland vegetation in the uplands of western Honshu, Japan, the present investigation was carried out at 32 localities. The grassland in the region is a secondary vegetation which has developed on part of deforested and disturbed areas, and is distributed in the uplands at the elevation from 400 to 1400m, mostly from 700 to 1100m. The origin of the grassland dates back to the 18th and 19th centuries when forests of the uplands were cut except for those on the higher mountains. Major grassland types in the region are the tall grass type dominated by Miscanthus sinensis, the sod grass type dominated by Zoisia japonica, and the bracken type dominated by Pteridium aquilinum, among which the first two types are prevalent throughout the grasslands. The first type is always found at the mowing grassland and at the new grazing grassland, while the second type at the old grazing grassland. The last type is infrequently found in the yearly burned grazing grassland. These three types do not differ from each other in their vertical range.
Intra-and interspecific chasings of immature butterfly fishes were studied in an exhibition tank (110cm×170cm×80cm) of the Suma Aquarium. Observations were made on 35 fishes belonging to 13 species in October 1961. For seven species, Chaetodon collaris, C. auriga, C. lunula, C. lineolatus, C. vagabundus, C. melanotus and Heniochus acuminatus, among which nine species had more than two individuals each in the tank, intraspecific chasing was far more frequent and eminent than the interspecific one. On the contrary, though only few data were available, the other two species, Chaetodon nippon and C. ephippium, appeared to chase fishes of other species as well as those of their own species. For the remaining species, it is at present difficult to conclude with certainty. Interspecific chasing of Heniochus acuminatus is concentrated mainly to H. singularius, and the latter chased the former back, but hindered no other species. This may suggest that fish is likely to chase a fish of another species of shape and colour resembling its own. The frequency of intraspecific chasing in any species was much higher before and during feeding than after, while the frequency of interspecific chasing decreased apparently before and during feeding.
1. The writer collected egg-batches of the cabbage moth, Mamestra brassicae from eight lacalities distributed from the northern to the south-western part of Japan, viz., Hokkaido to Kyusyu (Table 1). Observations were made on certain characters of larval, pupal and adult stages of these local strains by rearing the insects under the condition of 25℃, of complete darkness and with an initial density of 20 larvae per vial. 2. In the 4th and 5th instar, the Tokyo and Kyoto strains showed higher values in the measurement of head width than those of the strains from the northern and the south-western localities (Fig. 1 and Table 2). 3. The larvae of the northern strains tended to be darker in their skin color and shorter in their larval developmental periods than those of the south-western atrains (Fig. 3). 4. The pupae of the Sapporo and Oita strains were less in weight than those of the Honsyu strains (Table 7). The ratio of the mean pupal weight to the mean length of larval duration was the largeat in the Sendai strain, and it decreased northward as well as south-westward (Fig. 4). 5. The pupae of the Sapporo strain were of non-diapausing, but those of the Honsyu and Kyusyu strains were a mixture of non-diapausing and aestivating types. Furthermore, both the non-diapausing and aestivating pupae of the south-western strains required longer time for pupal development than those of the northern strains (Fig. 5). 6. The sdults of the south-western strains were characterized by their longer life, and shorter duration of their oviposition period, as compared with those of the northern strains. Also, the female moths from the south-western localities deposited less numbers of eggs than those from the northern localities (Table 9).
It was tested in the experimental population of the azuki bean weevil, Callosobruchus chinensis, whether a balance of population exists when the density independent mortality such as constant percentage of artificial removing or adding influence the population. The experiment was done under the controlled condition of 30℃ and 75 per cent R.H. supplying with a constant amount of azuki bean as food. In the present experiment, various percentages of insects were removed from or added to such population in every generation, and it was analysed how the steady state is altered under such a condition. Removal of a given percentage of weevil was made in every generation by heat treatment of required percentage of the bean which contained the insect, just before the adults emergence. Removing were 0,25,50,75,90 per cents of the level of steady density (Experiment A). Adding the insects into the population was during the first six days of the emergence period, in which number of adults added were determined as percentage of expected level of steady state in the control culture. Percentage of adding were 0,25,50,75,100 (Experiment B). In any case of the removing or adding, the population maintains a steady level of population density, and in some cases, damping oscillation was obserbed, and the level of population is concave to upwards or convex downwards before the population reached a steady state. The more increase of removing or adding percentage follows the more compensatory rise or fall of the steady density (Fig. 1,2). Several generations were required before the population reached its steady state, but when the strong disturbance of the population as 90 per cent removing was done, and the variation of the steady level of the population was enlarged in four replicates, and the population was difficult to reach its steady state after several generations elapsed (Fig. 3). From such affairs, it should seem that the chance element is important when strong a disturbance may influence population. The rate of reproduction between two consecutive generations was dependent on the intensity of competition and varied from 11.75 in 90 per cent removing the population to 0.48 in 100 per cent adding population (Fig. 4). The result of this experiment clearly indicates that a balance of the population exists, and the insect population must be in a balance with the density independent condition to which they are subjected at any density.
The field study was carried out during the period from 1960 to 1961 and more than 112 species belonging to eight orders of benthic insects were collected. Of these insects, 71 species were found in the head-stream, 69 in the torrential part of the river, 67 in the middle part and 19 in the lower part. In the summer, four pools were surveyed in this river. On the bottom of these pools, the dominant species are mayfly nymphs such as Ecdyonurus yoshidae, Potamanthus kamonis.
In the adjacent waters of the Oki Islands, Japan Sea, 219 collections were made by a horizontal surface haul with the 1.3-metre larval net in the years of 1957 to 1960. Seventy one species beionging to 44 families of fishes were collected in this period of survey. The dominant species among them are Engraulis japonica (HOUTTUYN), Cololabis saira (BREVOORT) and Upeneus bensasi (TEMM. et SCHL.), and they occupied 92 per cent of the total number collected. As for eggs, Engraulis japonica occupied 42 per cent. Up to the present, these three species have been scarcely utilized as fisheries resources in this area. In most species, the eggs and larvae are distributed in the sea areas of the continental shelves, but Engraulis japonica and some other fishes are distributed in the deep sea area as well. Eggs of Watasenia scintillans (BERRY) occurred mainly in the deep sea area.