Population fluctuations and natural mortalities of the pine‐moth, <i>Dendrolimus spectabilis</i>

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  • Atsushi Kokubo
    Institute of Forest Zoology, Faculty of Agriculture University of Tokyo Tokyo

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<jats:title>Summary</jats:title><jats:p>Annual changes in the population of the pine‐moth, <jats:italic>Dendrolimus spectabilis</jats:italic><jats:sc>Butler</jats:sc>, were studied in Kashima district. The insect completes two generations in one year, and the adult emerges in early summer and again in autumn.</jats:p><jats:p>The insect population showed fairly drastic fluctuations in the past years, and a conspicuous peak was recorded in three times, in 1950, 1955 and 1961. It was noted in each of those three years that a great number of adults of the summer generation emerged in autumn. The main reason for this great abundance of the insect population seemed to be high survival rate of the young larvae in summer. It was suggested that the climate in July had powerful influence upon the survival f thos e young larvae.</jats:p><jats:p>The effects of natural enemies were usually the greatest on the egg population of the pine‐moth in either generation. Much greater number of insects in the overwintering generation was destroyed by parasites and diseases than in the summer generation. Finally, a rapid increase of the insect population in autumn was considered to be caused by a combined effect of climatic conditions and of natural enemies.</jats:p>

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