Larval and egg populations of P.rapae crucivora were affected by mechanical detachment of eggs from host plant leaves, drowning of larvae by rainfall and by such natural enemies as spiders, Polistis wasps, Hyla arborea japonica, Apanteles glomeratus and Pteromalus puparum. In April, a remarkable reduction in the numbers of eggs and 1st instar larvae was mainly induced by abiotic factors while that of 5th instar larvae was mainly caused by biotic factores. In June and July, a remarkable reduction in the numbers of eggs, 1st and 2nd instar larvae was observed mainly due to the predation of micryphantids. Then, the suriving mature larvae were preyed on mainly by Polistis wasps. Therefore the surviorship curves were concave in June and July. In October, only eggs and 1st instar larvae were affected by abiotic factors before the survivorship curve levelled off.
In a subalpine Abies veltchii forest characterized by"dead trees strips", the age-dependent change of stand structure and dry matter productivity was investigated near Mt. Asahi, Yamanashi Pref. Rapid increase of the needle biomass towards a maximum during about 40 years after emergence of the seedlings was followed by a gradual decline and a relatively long stable stage, after which the needle biomass decreased remarkably when the trees were over 100 years of age. The net production related to stand age showed the same pattern in needle biomass, so the peak of net production, 11.9 t/ha・yr, was observed in a 37-year-old stand holding the maximum needle biomass of 17.1 t/ha.
The early life history of the land-locked miyabe char, Salvelinus malma mlyabei OSHIMA, was investigated in an inlet stream of Lake Shikaribetsu in central Hokkaido from 1971 to 1974. The ontogenetic process of this species was divided into seven developmental stages according to the ETAP theory of Vasnetzov. A relatively high proportion of drifting terrestrial insects was found in the food of all developmental stages except the alevin in every season of the year. Two developmental stages were found among juvenile fish which migrated into the lake. One stage consisted of smolt and/or presmolt-like fish which were 2 years or more old and varied from 105 to 155 mm in fork length. Migration occurred in June and July. Another stage consisted of relatively younger fish of different age and size classes. They migrated into the lake from July to Novemeber with a peak in October. It was suggested that these fishes were using the lake as a wintering area, since, of all the available water sources, it maintains the highest water temperature during the winter season.
Ercolania boodleae (BABA) occurred throughout the year, being especially abundant from winter to early summer, on the coasts of Sado Island. The animal tended to congregate on a green alga Chaetomorpha aerea. The population of the animal settling on this alga consisted of much larger individuals than those which had been confined within the predominatly Ulva, Enteromorpha or Cladophora isolated localities. Under laboratory conditions, the animal was affected considerably by the alga supplied. The efficiency of animal nutrition, which was determined on the basis of the size increase, reproductive activity and viability, was found to decrease in the following order : Ch. aerea>Ch. moniligera>Cl. densa>Cl. rudolphiana≧the algae belonging to the Ulvaceae and Bryopsidaceae. In selecting food the animal's tactile sense of the physico-chemical properties of the algae may play an important role. In addition to this it was also considered that the distribution of the animal is changed occasionally by wave action, and that the animal may produce three or more generations in a year.
A detailed faunal survey of ants was done for the first time in the Tohoku District. Seventy species of ant were recorded from Miyagi Prefecture of the Tohoku District. They contain almost all the species which are known to live in the Tohoku District. The regional generality of occurrence of each species was compared by the number of the localities of collection. In this study several species were designated as common ants. The change of the ant fauna with altitudinal change (0-1820m) was also examined. The result indicates that the number of species increases with decreasing altitude for every subfamily, but this tendency is rather slight in Formicinae as compared with the other 3 subfamilies. The ant species were grouped into 9 types based on their ranges of vertical distribution.
A mathematical model for the formation and the development of a distributional pattern in a population is presented. The influence of reproduction on the distributional pattern is investigated by using the technique of the branching-Markov process and the index of aggregation, CA, is calculated as a function of six characteristic parameters introduced in this mathematical model. The dependence of CA on the parameters is discussed comparing the results with the experimental formula obtained from simulation by KUNO.
Female P.jenynsii deposits prepupa on the host-roosting quarter except host-hibernating quarter. Intervals between depositions were about 5 days. Pupal period was about 20 days. Both the interval and period of prepupal deposition became shortened with the rise of experimental temperature. After the bat died away, the majority of flies also died within 24 hours. This indicates that blood-sucking is necessary at least once a day. Wintering flies sucked blood intermittently and lived for at least 4 months, but did not propagate. Average infestation number per host was 0.1-0.3 in winter and 0.2-0.7 in the other seasons. The low density per host throughout the year may primarily be due to host-predation and secondly due to density effect of fly. Periodic fluctuation of the average infestation number from April to September is largely caused by synchronization with the breeding cycles starting soon after awakening. The more bats grew, the more they were infested, its tendency being marked in adult females. Infestation degree corresponded presumably with the degree of hosts' activity at their roost. It was considered that specific and adaptive host-parasite relationship was ecologically influenced by duration of bats' roost utilization, activity at roost, size of cluster and flying pattern, together with the life history of flies.
Five species of cellular slime molds, Dictyostelium mucoroides BREFELD, D.purpureum OLIVE, D.discoideum RAPER, Polysphondylium pallidum OLIVE and P.violaceum BREFELD, were studied in soils of Castanea crenata-Quercus serrata forest and in soils of mixed forest of Pinus densiflora and deciduous broadieaved trees in the Tenryu River region of central Japan. The slime molds under study were more abundant in the soils of the former forest type than in those of the latter. D.mucoroides occurred most frequently throughout both forest types, followed by D.purpureum and P.pallidum, while D.discoideum was found only in the chestnut forest soils.