ニカメイガ卵のふ化の斉一性と幼虫集団の形成について

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In the previous paper (1962 a), the authors studied the influence of larval aggregation of the rice stem borer, Chilo suppressalis, upon its survival. In the present paper, the authors intented to know the influence of the synchrony of hatching of individual eggs within an egg mass on the formation of larval group in a paddy stalk and on the behaviour of larvae from hatching to aggregation at the first feeding site. These experiments were carried out under the natural condition of room temperature and natural daylength. The results obtained are summarized as follows. 1) Hatching of eggs within an egg mass of large size was well synchronized and it took 13 minutes in average for completion of hatching in contrast with a small one of 20 minutes, in which the variation of hatching time between first and last in each mass was great. 2) When an egg mass of large size was separated into some pieces at 2 days before hatching, any neighbouring piece did not hatch one after another, but hatched independently and it took time more than 2 hours from the beginning of hatching of the first piece to the completion of the last one. Therefore, the time from hatching to its completion was greatly protracted. 3) When several eggs within a large sized egg mass was killed by needle at random 2 days before hatching, the time between the first and the last hatching in a mass was also greatly protracted and it took time more than 1 hour. 4) At the 3rd day after hatch the degree of larval aggregation in a rice plant stalk was maximum in the large sized egg mass and the minimun in the mass where several eggs were killed randomly by needle. 5) In most instances, the larvae tended to move toward the tip of rice plant leaf. Some remained motionless there, others turned around and followed the leaf surface back to the base of the leaf and one of these larvae which reached to the feeding site (leaf sheath), wandered around here and there for a moment, thereafter it confluented with others. The larval group was gradually enlarged in its size and established at the feeding site. An isolated larva could not feed. When the hatching of eggs within an egg mass was well synchronized, the degree of larval aggregation was high. On the other hand, if the synchrony of hatching was disturbed by such a factor as parasitization, establishment of aggregation was also disturbed. It is concluded that synchrony of hatching and the behaviour of newly hatched larvae influence the size of larval group and larval survival.
日本応用動物昆虫学会の論文
1962-09-30

ニカメイガ卵のふ化の斉一性と幼虫集団の形成について

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