where ALL_<ST> stands for the Average Leaf Longevity (ALL) of the undefoliated plant and ALL_h means that of a mechanically defoliated plant h which is otherwise under the same conditions as the undefoliated Standard. DPX can take account of the three factors, timing, frequency and severity, of the intensity of defoliation pressure in one term. The application of DPX in some practical cases clearly demonstrated negative correlations between DPX and variables such as the standing crop of leaf area in the following early growing stage, volumetric wood growth of young tamaracks, average annual yield of range grass. These results suggest that DPX is strongly applicable in examining various aspects of ecosystem where defoliation, whether by intention or by chance, plays a crucial role.
Two species of Lygaeid bugs, D. pallipes and D. japonicus, have two wing forms, macropterous and brachypterous. A field study was carried out in 1975 and 1976 to clarify the relation between the frequency of appearance of two wing forms and environmental factors. The frequency distribution of relative wing length in those two species was relatively discontinuous as compared with that of the related species Cavelerius saccharivorus. In both species, frequency of macropterous form was higher in the 1st (summer) generation than in the 2nd. A closer examination of the relationship between the appearance of macropterous form and local density in the summer generation indicated that macropterous form would appear when the density exceeded a certain threshold. These results are generally similar to those reported for C. saccharivorus, but the percentage of macropterous form seems to be considerably lower in the two species reported here. Such a difference might be related to the difference in stability or persistence of their habitats ; D. pallipes and D. japonicus live on wild perennial plants (Phragmites and Miscanthus respectively) whereas C. saccharivorus mainly lives in cultivated fields of sugar cane.
Existing vegetation maps of the Korean Peninslla were compared to reveal the common features involved. The thermal climates of the five representative forest types were determined in terms of the warmth and the coldness indices, based on the most detailed maps, those by Ueki (1933), Lautensach (1935) and Yim (1968). The northern boundary of the warm-temperate evergreen lucidophyll forest zone was examined in detail with reference to the distribution of its component species. Taking the results of the three preceding papers and those of Japanese studies into consideration, it was concluded that the four principal forest zones and two subzones more or less commonly recognized by the preceding authors were-distributed-in the Peninsula in close correlation with the distribution of thermal climate.
The two sibling Drosophila species, D. simulans and D. melanogaster, are believed to coexist in nature sharing food and space. However, D. simulans prefers a semi-natural environment while D. melanogaster lives near human habitation. A weak seasonal isolation was observed between the two species, i.e., a unimodal population distribution peaking in August was found for D. melanogaster while a bimodal population distribution peaking in July and September was found for D. simulans.
Makura moor is situated at the place of 720 m above sea level at Geihoku-cho within the Chugoku Mountains, in the northern part of Hiroshima Prefecture. From the results of pollen analysis, four major vegetational changes for approximately the last 10,000 years were recognized in the pollen diagram from the bottom to the surface. 1. Tsuga, Pinus (Haploxylon type), Picea, Betula stage (190-170 cm, 10,000-9,000yr B.P.) (R-I zone). 2. Cyclobalanopsis, Lepidobalanus, Alnus stage (170-80 cm, 9,000-4,000yr B.P.) (R-II zone) 3. Lepidobalanus, Cyclobalanopsis, Alnus stage (80-60cm, 4,000-1,500yr B.P.) (R-IIIa zone) 4. Pinus (Diploxylon type), Cryptomeria, Lepidobalanus stage (60-0 cm, after 1,500yr B.P.) (R-IIIb zone) The vegetational history can be regarded as the common one for the period from the postglacial age to the present time in the Chugoku Mountains, with one exception of Cryptomeria, the number of pollen of which is included in low percentage in the second and third stage compared with the results of another moors, such as Yawata moor, Sugawara moor, Kabosaka moor and etc.
Population fluctuations and spatial distributions of natural enemies of aphids were investigated in unsprayed corn fields. The densities of the aphids, Rhopalosiphum padi, R. maidis and Macrosiphum akebiae, were very low in the study areas and their spatial distributions were highly contagious regardless of the size of sampling unit. Natural enemies (coccinellids, syrphids, lacewings, etc.) were abundant in the years when the densities of the aphids were high, but they did not show any clear tendency to aggregate on localities of higher densities of the aphids, and in particular the distribution patterns of adults and larvae of the enemies were mostly random or uniform. The abundance of the enemies seemed to be sufficient for suppressing the aphid populations, and it also seemed that the natural enemies affected the spatial distribution patterns of the aphids. The environments in the unsprayed corn fields without weed control seemed to facilitate the action of the natural enemies.
Social behavior of the Japanese wood mouse was studied by trapping and by direct observation at two artificial feeding sites during the early part of the breeding season. Meetings were classified into the following five types : aggressive meeting, meeting with retreat, meeting with mutual flight, tolerant meeting and amicable meeting. Amicable meetings and meetings with mutual flight were observed only between opposite sexes. Males always expelled other males from the feeding site when they met, and a straight dominance hierarchy was observed, although their ranges overlapped rather randomly. The subordinate males had somewhat different activity rhythms from those of the dominant. On the other hand, ranges of females tended to be mutually exclusive, but females permitted other females to stay near the feeding site. All females had similar activity rhythms. The social order seemed to be related to the body weight, but males were dominant over females, even if the male was smaller than the female. Although males often took the bait together with females, no evidence that a male associated with a particular female was obtained.
Generally, a mussel population on a concrete wall cannot survive for an extended period, but will tend to perish in two to four years. Populations living on exposed surfaces grow vigorously, but are short lived, while those on protected surfaces are not so flourishing, but they seem to possess a longer life span. Whether the life is long or short, a mussel population appears generally only once. However, in some cases, at poorly lit sites, several generations settle intermittently. Secondary settlement of mussels never takes place in an area where algae occur abundantly, rather, places of resettlement are characterized by lesser development of algae, and these areas are faunistically poor. The barnacles Balanus amphitrite hawaiiensis BROCK and the tube worm, Hydroides norvegiva GUNNERUS sometimes influence the normal fluctuations of mussel populations.