マツのシンクイムシ類の自然個体群における密度効果について
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概要
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Evetria cristata WALSHINGHAM and Dioryctria splendidella H.-S. are well known shoot moths attacking pine trees. The former causes damage to the shoot and cone, but the latter further to the stem. The present auther has carried out experiments on the following items to ascertain the density effect acting in natural populations of both species : the larval mortality in two different population densities, one larva and five larvae per a small pine seedling ; the influence of the injury by the shoot moth on the cone growth ; and the mortality of the hibernating generation in the cones in which some of them have been attacked by the larvae of the previous hibernating generation. One (low density) or five (high density) individuals of the first instar larvae of D. splendidella were laid in the shelter of the bud scales of the top shoot of each small pine seedling, Pinus thunbergii or P. densiflora. The dispersal of the young larvae was limited only to the top shoot area during 20 days after they were laid, their mortality was, however, higher in the low density than in the high density. There is no difference between the survivour-ship (l_x) curves in the low and high densities after the 11th day. Cone damaged by the previous hibernating generation of E. cristata and D. splendidella does not appear to be a favourable site for the oviposition of E. cristata adult of the generation. But, it seems to be superior for the larval growth. Because the mortality of the population living in the undamaged cone is significantly higher than that in the damaged cone at 5 per cent level.
- 日本生態学会の論文
- 1965-04-01
著者
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