摘要：

Investigations were carried out at Asso, Wakayama Prefecture on the 1st, 2nd and 3rd generations of the southern green stink bug, Nezara viridula L., during the period of 1961-1962. With regard to the unparasitized eggs, there was no consistent relationship between the hatchability of eggs and the size of the egg mass, except that the small sized egg masses tended to contain a considerable number of unfertilized eggs. Parasitism is often responsible for an apparent regularity between the hatchability and the egg mass size, e.g. the 2nd generation in 1961 and 1962. It was considered that this was resulted from the bias relative to time both in the activity of parasites and the frequency distribution of egg mass size of the host. It was revealed by the key-factor analyses that the mortality during the 3rd instar affected mostly on the total mortality from hatching up to the 4th instar. And that the mortality of the 1st instar larvae was mostly constant irrespective of the size of the larval aggregation ; that of the 2nd instars also remained almost constant except for the small aggregations which showed a higher mortality ; whereas the mortality of the 3rd instars reduced with an increase in the size of aggregation. The predation of spiders, a "constant number" type of mortality (SOLOMON, 1964), was suspected to be one of the factors giving rise to such a differential mortality of the 3rd instars related to their aggregation size. The survival value of the aggregation of the 2nd instar larvae observed in the laboratory (KIRITANI, 1963) was not detected under the natural conditions. It is concluded that the larger the initial size of the larval aggregation, the higher the survival rate of the aggregation becomes. This means that the numerical contribution of the large aggregation is far greater than that espected merely from the survival rate.

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