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  • 1
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary To assess the population productivity of the grasshopper Parapleurus alliaceus Germar in a Miscanthus sinensis Anders. grassland, estimates of population density, survival, and dilution rates were attempted using the mark-release-recapture method. No significant departure from the random-catch hypothesis, which is the basic pre-requisite for the estimation of population parameters, was discovered. A comparison between the results of two experiments, attempted simultaneously in the same area of the grassland, indicated that the accuracy of the mark-release-recapture method was acceptable for our purpose. The population trends in 1968 and 1969 showed that mortality during the early nymphal instars was remarkably low (75% and 62%, respectively, for the period from the second instar nymph to adult), and that adult longevity was greater than 10 days. The number of nymphs hatched in 1969 was smaller than 1968, and the cause of this reduction was thought to be the predation of eggs during autumn and winter.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary During the course of a 10-year investigation on the population dynamics of Dryocosmus kuriphilus, a rapid decrease in the number of individuals was noticed in the adult stage. To detect the role of predation by spiders in causing this high adult mortality, spiders collected from the survey station were tested for their reaction to Drycosmus antiserum. About 20∼50% of the spiders collected during the emergence period of D. kuriphilus reacted positively, showing that the species of Thomisidae, Argiopidae, Agelenidae and Salticidae were the important predators. The predation ratio for the total adult wasp population was estimated at 8.1% in 1968, 20.2% in 1969 and much higher in 1970, increasing with decreasing population density of the wasps. However, the predation by spiders could not account for all of the adult mortality of D. kuriphilus.
    Type of Medium: Electronic Resource
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