Seasonal and annual change of a folivorous insect guild in the Siebold's beech forests associated with outbreaks of the beech caterpillar, Quadricalcarifera punctatella (Motschulsky) (Lep., Notodontidae)

Seasonal and annual change of folivorous insects of beech associated with outbreaks of the beech caterpillar, Quadricalcarifera punctatella , were investigated in northern Japan from 1988 through 1992. Lepidopteran larvae sampled from branches and fallen frass were used for the analysis. Sixty‐nine species were found over a 5 year period. Most species in the families Tortricidae, Geometridae, and Noctuidae infested in early seasons in the year, while Notodontidae fed in late seasons. Although the number of species decreased, the size of those infesting became larger in later seasons. There were three peaks in seasonal changes of falling frass: the first was in June and was constant over the years and locations; the second, caused mainly by Q. punctatella in August, varied greatly among years; and the third peak was sometimes ambiguous. Total frass was strongly influenced by Q. punctatella density. The density of this species changed with a magnitude of 10000, but the weight of frass produced by the other folivorous insects was estimated to fluctuate 10 times at most. The frass of other insects decreased the year following conspicuous defoliation by Q. punctatella . The results indicate that delayed induced response of the Siebold beech caused by Q. punctatella influenced not only the species itself but also other folivorous insects. Q. punctatella was the main factor determining the biomass of folivorous insects in the beech forests in northern Japan during the period studied.