The distribution of the female adults of the mulberry scale on each twig of the cherry tree, the plum tree and the mulberry tree was recorded, and the mortality and oviposition rates were surveyed to elucidate the phase of dispersion and its ecological significance ; on the other hand in the laboratory condition of 25℃, the number of eggs laid on the tuber of the potato by a female adult and the phase of dispersion of the nymphs hatched from these eggs were surveyed. The results are : 1) The individual number of the female adults settled on each twig suits the following equation, which was first proposed by KETTLE(1951), log y = log a +bx, where y represents the individual number at the distance x from the crotch of the twig. 2) The number of eggs laid by a female adult at a constant temperature of 25℃ was 99.7 on an average, while in the field 11 on an average of the nymphs from a female adult settled on the twig of the mulberry tree. Accordingly the mortality in the course of the dispersion was estimated to approach 89 per cent in the field. 3) The mortality of the female adult was about 30 per cent on an average (including the sterile female) from the settlement on the twig to the oviposition time, and it was higher towards the center of the dispersion. 4) Although no relations were recognized between the number of the eggs embraced by a female adult and its settling position on the twig, the rate of the sterile female adults were higher near the crotch of the twig and accordingly the oviposition rate on the whole was lower there. 5) The sex ratio, ♀/(♀+♂), of the nymphs which were laid by hibernated female adults was higher the top of the twig.
Intra-and interspecific relations of 43 species of saltwater fishes were studied by the chasing behavior in seven exhibition tanks and one experiment tank of the Suma Aquarium. The observations were carried out in Nov. 1961. By comparing the frequency of intraspecific chasing with that of interspecific chasing for each species, 15 species, Kuhlia taeniura, Diploprion bifasciatus, Girella punctata, G. melanichthys, Lethrinus haematopterus, L. choerorhynchus, Gymnocranius griseus, Hapalogenys nitens, Therapon jarbua, T. oxyrhynchus, Abudefduf sordidus, Microcanthus strigatus, Prionurus microlepidotus, Siganus fuscescens and Stephanolepis cirrhifer, are recognized as the intraspecific chasing type. Other eight species, Epinephelus fasciatus, Lethrinus nematacanthus, Amphiprion xanthurus, A. frenatus, A. chrysogaster, Tetradrachmum trimaculatum, Tridentiger trigonocephalus and Abudefduf vaigiensis, are regarded as the nonspecific chasing type. These chasing types were compared with social behaviors in the open sea. It was found that intraspecific chasing type correlates with the schooling behavior in the natural habitat and the nonspecific chasing type correlates with the assemblage and solitary behaviors.
This paper deals with the division of labor among individuals constituting the Polistes colony. Since the Japanese apecies of Polistes are monogynic, the labor is divided among workers in the superindividual stage, the founding female being then nothing but an egglaying machine. There is a tendency that older workers are in charge of the intracolonial tasks. Younger workers spend most of their time at rest, taking occasionally cell patrol, while middle-aged ones are mainly engaged in foraging. There is, however, no definite division of labor observable among them which is determined by their age as is the case with honeybees. Nevertheless, some extent of division of labor is certainly acknowledged in the Polistes colony and is considered as a factor by which the organization of the colony is maintained. In addition, distinction between a superorganism and a superindividual was discussed. It is more reasonable to regard the association of a founding female with her workers (excluding fertilizable females for the next generation) as a superindividual rather than to consider the whole colony as a superorganization.
Ecological studies of mycelial fungi were carried out in the Goshikinuma Lake Group of Volcano Bandai, Fukushima Prefecture, Japan. The lake waters contain large amounts of mineral elements and show strong acidity. The mycelial fungi were counted to be 1500〜3000/l in water and 150〜2000/g in bottom muds. The differences in the amounts of the fungi were observed between acidotrophic and harmonic lakes. The genus Penicillium is dominating both in waters and muds. The vertical distribution of the fungi in water has correlation with that of dissolved oxygen. The fungi are distributed mostly in epilimnion.
Using the azuki bean weevil, Callosobruchus chinensis, and its larval parasite, Neocatolaccus mamezophagus, it was examined whether the balance of interacting system of the host and its parasite exists when the density independent mortality such as artificial removal of constant percentage of the population has influence upon the host-parasite interacting system. Under the condition controlled at 30℃ and 75 per cent R.H., various percentages of both host and parasite populations (exp. HP), or host population (exp. H), or parasite population (exp. P) were removed from the original population of the host-parasite system in every generation respectively, and how the steady state is altered by these treatments was examined. The methods of removal are as follows : In the experiment HP, a fixed percentage of beans which contained such percentage of host and parasite as 25,50,90 of the level of the steady density were heated just before the host emergence and removed. In the experiment H, during about one week, the host was removed every day, every two days, every three days from the time of adult emergence. In the experiment P, when the host is a full-grown larva and the parasite can easily lay its eggs in the host from outside the bean, the parasite was removed every day, every two days, every three days the from the 14th day after host oviposition. In experiment H and P, percentages of such removing as mentioned above were calculated as 70,80,90 per cent of the control population. In any case of the removing, the host-parasite system maintains a steady level of population density (Figs. 1,2,3). But the steady state of each removed population changes its level from that of the unremoved population as shown in Table 1. When the host was removed, the parasite density did not so conspicuously fluctuate as the host density (Fig. 2), and when the parasite was removed the trend of fluctuation seemed to be the reverse (Fig. 3). Unless the host density attains a saturation level, the steady density of it depends upon only the intensity of competition in the parasite population. After the host population reached such a state, the steady state of the host becomes higher in a single population of host than in the host-parasite system (Fig. 6). This difference in the steady density is due to the action of the parasite, which is highly influenced by the host density or parasite density even under a constant physical condition. In the interacting system, though the parasite efficiency of host finding is dependent on the density of the host, the probability that the deposited egg of the parasite developes into an adult parasite in the next generation is dependent on whether it is able to get away with hyper-parasitism. The probability that the egg of the weevil develops into an adult weevil which will be the individual of final density of the host population in the next generation depends on whether host can survive from attack of the parasite. Of course, the probability that the egg of the weevil is deposited by the individual of final density of the host developes into the individual of initial density of the host in the next generation is only dependent upon the density effect of the host population. This is because the host population is subjected to attack by the parasite for only a fraction of its developmental period just before host emergence. In any case of the removing, the host-parasite system maintains a steady level of population density. But the steady state of each removed population changes its level from that of the unremoved population as shown in Table 1.