Even when marked S. litura male moths were released 3m apart from virgin female traps, the result of trapping in the night of release was rather complicated and variable. There was no correlation between the trapping intensity and the distance so long as the moths were released within 200m of the traps. Some of the moths which were released 500m or 1,000m apart from the traps were recaptured in the very night of release. Trapping data after the night of release were also dealt with. Traps in close proximity to 20 watt blacklight tended to be avoided by the marked males.
In der alpinen Stufe der japanischen Hochgebirge kommen die alpinen Vegetation, Strukturboden, Blockfelder und Schneeboden zusammen vor, trotzdem sie eigentlich in differenzierten Hohenstufen entstehen muβten. Dadurch wird das Bild der Naturlandschaft in seiner Deutung kompliziert. Der Verfasser untersuchte die Koexistenz der einzelnen Vegetationsgesellschaften mit den Strukturboden. Diese Koexistenz-Wettbewerb-Verhaltnisse wurden mit den klimatischen und lokaiklimatischen Bedingungen verglichen. Der Untersuchungsbereich liegt in der alpinen Stufe des Kisokomagatake (2,956m u.d.M.) in den Japanischen Zentralalpen.
The sexual and physiological character of the adults of Fannia scalaris F., which swarmed and mated under the willow street tree, was studied from 1957 to 1960 in Sendai. Individuals alighted on the tree and being in each stage of the mating behavior were caught and examined as to sexual characters, physiological age and impregnation of the females. The results are as follows : Only physiologically old maies swarmed and carried out mating behavior. They pursued other individuals indiscriminately and tried to mate, but finally only the pairs of old male and physiologically middle aged unimpregnated femaie copulated. Females seemed to copulate only once in this species. From the studies mentioned above, it was concluded that the swarming of this species was the precopulation behavior and each stage of the mating behavior was the most effective serching process of males for unimpregnated females in trial and error.
Severe winter cold and summer drought prevail on permafrost in Yakutis plain. The water penetration in a deep ground is prevented by permafrost, and thaw or rain water is retained in the active layer in which soil remains unfrozen in summer (about 60cm in depth in dense forests). Thus, the forest zone expands to the summer drought area in permafrost regions. Dahurian larch roots expand in the soil down to 5 to 20cm-depth. And the soil temperature and the water content at 20cm-depth were respectively 3.6℃ and 15 per cent on August 12. Thus, the low soil temperature and the low soil water content are among the most important factors limiting the tree species growing in dry and high latitudial permafrost regions. In the permafrost areas containing massive ice veins, clearing of forests causes the development of the thermokarst depression with steep sides and a flat floor covered with grass, called an alas. Regeneration of forests does not occur in alases. Forests contribute to prevent melting of the groundice. On the contrary, permafrost allows forests to grow even in summer drought areas. Thus, it appears that there is an intimate relation between forest and permafrost.
The euterrestrial amphipod population of Orchestia platensis japonica, is intricately constructed of three different phases, viz. (1) age (instar) ; (2) generation ; and (3) subpopulation. The breeding period occurs twice a year, viz. during late May to mid-July and late July to late September. Recruitment during these periods are called the 'spring type' and the 'autumn type', respectively. The life cycle of this population is one year. The spring type produces only the next spring type, while the autumn type exclusively the next autumn type. Individuals of each subpopulation show a sigmoid pattern in their body growth. The animal hatched as spring type overwinters at the 10th or 11th in age, that is just before the adult stage. It becomes an adult next spring and then breeds. On the other hand, the animal recruited as the autumn type overwinters at the 6th or so ages. After wintering the animal begins to grow again and breeds in early autumn. The tendency towards the reproductive separation of the two subpopulations is considered to be a possible prestep to an allochronic speciation.
Reproduction of the mosquitofish, a freshwater fish natively distributed in North America, was studied in two ways, viz. in the natural population in Tokyo and in the laboratory experiments especially on its environmental factors. Experimental results showed that the "critical day length" of this fish is between 12.5 and 13.0hrs. This approximately accords with the natural reproductive cycle. Reports on the reproduction of this fish are discussed.
The Nagase-gawa, a remarkable acidtrophic river, is the largest one among the inflows of Lake Inawashiro-Ko. The attached algal flora of this river and its tributaries were studied in July, 1972 and May, 1973. Values of pH of water at stations 1,2 and 3 were very low. At these stations, the standing crops were poor and the floras were different from those of the other stations. At these three staions, diatoms, green algae and a protozoan were found abundantly. It seems to be interesting that blue-green algae can not be found at all at the stations where pH values of water are low, though at the stations (Sts. 4,5,7 and 8) where the pH values are nearly neutral, Homoeothrix janthina and the other blue-green algae were found in abundance.