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SUMMARY
Body size of Q. punctatella at first increased with population density, but became very small the year following an
outbreak. Its size was still small 3 years afterwards. Because adult size greatly influences fecundity, this was a factor in
keeping Q. punctatella density low for several years after an outbreak. As for food quantity, severe defoliation caused a
decrease in the amount of leaves the following year, and this limited the peak density. The defense strategy of beech in
relation to severe defoliation changed as time passed. In the year following severe defoliation, nitrogen content decreased
and tannins increased; this resulted in high mortality and small body size in Q. punctatella. Three years after an outbreak,
nitrogen content recovered to the same level as prior to defoliation, but tannins were even higher. This active, induced
defense kept larval survivorship low. Maternal effects were also recognized; the quality of Q. punctatella was poor even 3
years after an outbreak. Thus, food deterioration and the correlated results of maternal effects suppressed Q. punctatella
density for several years after an outbreak.
ACKNOWLEDGMENTS
We would like to sincerely thank Dr. Garry J. Piller (School of Environmental Earth Sciences, Hokkaido University)
for his kind advice and discussion.
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