The larvae of Mamestra (Barathra) brassicae (L.) were reared from hatching to pupation under solitary and crowded (10 individuals in a vial) conditions at a constant temperature of 25℃ in darkness on young leaves of the rape, Brassica napus L. Observations were made on the amount of food consumed by the larvae, the body weight of larvae and resulted pupae, and the dry weight of excreta of the 4th, 5th and 6th (final) instar larvae. The results of the observations are summarized in Table 1. Comparing with the solitary larvae, the crowded larvae consumed a larger amount of food in the 1st and 2nd instars, but less in the 4th and 5th instars. In the 3rd and 6th instars, no remarkable differences in the food consumption were observed between the solitary and crowded larvae. The total amount of food consumed in the larval stage was about equal in both densities of rearing. The crowded insects were heavier in body weight in the 1st and 2nd instars than the solitary ones, but the reversed trends were observed in the remaining instars and also in the pupal stage. The smaller ratio of the body weight to the amount of food consumed was obtained in the crowded culture in all, but the 4th instar. The dry weight of the excreta was about equal in both the solitary and crowded larvae. However, the ratio of that to the amount of food consumed was slightly smaller in the crowded larvae than in the solitary ones.
The larvae of Japanese red house mosquito (Culex pipiens pallens) were bred in room temperature (20〜27℃) in various population densities (from an individual per 20cc (distilled water) to 80 per 20cc) using petri dish (56mm in diameter). In the first experiment, the breeding medium (the initial medium was distilled water) was not renewed. The sufficient food (dried yeast) was given. In one or three individuals per 20cc medium, the emergence occurs by 11 days after incubation, but in the higher densities, the longer period it takes. In the densities more than five individuals per 20cc medium, the emergence takes place after getting lower density (two or five per 20cc). In the second experiment, the breeding medium was renewed every day. The similar results are obtained except for the number of larvae which can live in a unit volume. In the third experiment, 17 larvae which had been bred for six days were divided into four ; one, five and six individuals per 20cc distilled water. The larva which is bred alone gets develope into an adult. In the case of larvae which are bred in five per 20cc initial medium the emergence is delayed. The larvae which are bred in five or six larvae per 20cc distilled water take longer developmental period. From the above, it may be concluded that the larvae require a definite volume of medium, in which they live, for the finishing their larval development, and thus the minimum volume per individual required for further development of larvae in each stage is calculated.
Ecological studies on the grassland vegetation were carried out in the southern parts of Hokkaido in the summer of 1960. These grasslands are distinguished by their habitats and physiognomy. They are classified into the following types according to their structure and dominant species. 1. Alt herbosa (Tall herbage)-Polygonum sachalinense type. 2. Upland meadow-Sasa type, Miscanthus type. 3. Low moor- Phragmites type. 4. Coastal meadow- Elymus mollis type. 5. Pasture grassland- Dactylis type. 6. Lowland meadow-Rudbeckia laciniata type. Also, these types, as above mentioned, may be expressed as follows according to the biological spectra. I tried to combine life forms of plants arranging in order RAUNKIAER's life form (1907), HORIKAWA and MIYAWAKI's growth form (1954), KUWABARA's leaf form (1960) and NUMATA's disseminule type (1947) in order to describe the biological spectra. In these forms, the methods of describing the growth form (shoot form and root form) and the leaf form are as follows. Polygonum sachalinense type ; G, Se, Lt, Rr, D_1 Sasa type ; G, Se-c, Lt, Rr, D_<4-5> Miscanthus type ; H, Se-c, Lt, Rr, D_<4-1> Phragmites type ; HH, Sc, Lt, Rr, D_<4-5> Elymus mollis type ; G, Sc, Lc, Rr, D_4 Dactylis type ; H, Sc-e, Lt, Rf-r, D_4 Rudbeckia laciniata type ; H, Se, Lt, Rr, D_4 The author revised a little, however, HORIKAWA's method of describing the growth form. Shoot form Se ; erect, Sb ; branched, Sc ; caespitose, Sp ; prostrate, St ; twining. Root form Rs ; straight root or straight rootstock, Rf ; fibrous or reticulate root, Rb ; branched root, Rr ; rhizome or stolon, B ; bulb and tuber. Leaf form La ; acerose, Ls ; succulent, Lc ; coriaceous, Lh ; hairy, Lt ; thin.
Auf Grund von den Ergebnissen der Analyse von den Pflanzendeckungen bzw. den Oribatidenzonosen, die in den vorgangigen Berichten I〜III mitgeteilt, wurden hier ihre gegenseitigen Beziehungen voneinander erforscht. Die Reichlichkeit der Oribatidenzonosen wurden, mehrere Charakteristika in Erwagung ziehend, zwischen den Bestandgruppen, die man nach den mehreren Charakteren der Vegetation verschiedenartig gruppieren konnen, verglichen. Im allgemeinen fanden sich reichere Oribatidenzonosen in den Laub- und Nadelwaldern als in den Wiesen, in den Sommergrunwaldern als in den Immergrunwaidern, in den Waldern mit den hohen Kronenpflanzen als in den Waldern mit den niedrigen, in den Waldern mit der komplizierten Feldschichtsflora als in den Waldern mit der einfacheren. Quercus mongolica var. grosseserrata Bestand unter den Laubwaldern und Larix platyphylla var. japonica Bestand unter den Nadelwaldern scheinen den Oribatiden die gunstigste Lebensstatte zu liefern. Die individuendominanteste Oribatidenfamilie war Scheloribatidae in den Wiesenboden, Oppiidae in den Laubwaldboden, und Oppiidae+Suctobelbidae in den Nadelwaldboden.
A survey of the spatial distribution of the rice plant infected by the yellow dwarf virus was made on three paddy fields, the percentage of virus infection being low on No. 1,middle on No. 2,and high on No. 3,and the result obtained was examined from statistical point of view. 1) Distribution of infected plant per quadrat did not fit the binomial distribution when the infection was low and middle, but showed overdispersion. In these cases, the distribution was well approximated by the negative binomial. 2) Effect of quadrat shapes on the distribution pattern of infected rice plants was examined by means of the index of dispersion (s^2/x^^-). When a fixed number of plant was examined in a sample unit, sampling along a line in right angles to the row gave the least value of the index of dispersion. 3) According to I_B-Index, presented by MORISITA (1962) for discribing dispersion of individuals, it was clear that the larger the quadrat size, or the higher the percentage of infection, the less grew the intensity of overdispersion, and the distribution approached the random distribution.
In the two experimental populations started with each 100 larvae just hatched out of one batch of eggs of the two races of cruclan carp (Kin- and Gengoro-buna) the growth of fry was studied during four months with some observations of feeding habits. 1. The mortality rate of the fry, which was much higher at the earliest period of the experiment than at the later periods, was so low as a whole that almost all the fry survived to the latest period. 2. In the later course the coefficients of variation of body length decreased owing to the increase in growth rate of the smaller group of the fry. 3. By the second month after hatching the relative height of the body to body length of the race Gengoro-buna had become significantly greater than that of the other race Kin-buna. 4. The fry of Kin-buna showed more intensive attacks on tendipedid larvae than Gengoro-buna at about a month from hatching. 5. When alarmed, the Kin-buna fry used to swim rapidly toward the bottom of the aquarium, while the Gengoro-buna fry to the water surface.