Abstract
Since 1990 we have studied population dynamics of the phytophagous lady beetles,
Epilachna vigintioctopunctata, E. enneasticta and Epilachna sp. 3 (aff. emarginata), (Coleoptera:
Epilachninae) in Padang, Sukarami (West Sumatra), Bogor (West Java) and Purwodadi (East Java),
Indonesia. These sites have distinctly different climate conditions, e.g. Padang has a typical tropical
rainforest climate without a clear alternation of wet and dry seasons, while Purwodadi has a strong dry
season of 6-7 months. We have conducted censuses at 3-7 day intervals, including mark-recapture of
beetles and construction of life tables for up to 9 consecutive years in order to clarify the seasonal change
in abundance and mortality of the populations. In most populations the adult number changed greatly
with the formation of high peaks from time to time at intervals of 6-12 months. Their increase or
decrease was gradual, progressing over 3-5 months. Even under conditions with sufficient amount of
rainfall in Padang, Sukarami and Bogor, oviposition intensity, number of the following immature stages
and, as a result, adult emergence frequently showed discrete peaks at a fixed interval. These “generation
cycles” were especially clear during the phase of population increase. There was no simple relationship
between the seasonal change in rainfall and that of the beetle populations. We also discussed the impacts
of the strong droughts in 1994 and 1997-1998 caused by El Niño, and the degree of synchronization in
the trends of the populations among the adjacent study sites.
