Evolutionary Biology and Population dynamics of herbivorous lady beetles in Indonesia

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We have performed various kinds of field studies and laboratory experiments on phytophagous ladybird beetles (Epilachninae) in West Java and West Sumatra, Indonesia, in 1990 and 1991. A total of seven Japanese and two Indonesian researchers have been participated in this joint study. The main outcomes are :(1) A total of 24 species of epilachnines belonging to 2 genera and 5 species groups were collected. They include at least seven new species.(2) Sympatric species with a similar body size often are closely similar, or virtually identical in external appearance, even though they are distantly related taxonomically.(3) It was revealed that morphology of female intrenal reproductive systems, mating durations, and modes of sperm transfer are highly valuable for the classification and phylogeny reconstruction of Asian Epilachninae.(4) Food plants were confirmed for 23 epilachnine species. Epilachnines of the same species group tended to occur on one or a few restricted plant families.(5) The population density of most species, except for those on crops or weeds, was revealed to be very low.(6) Two types of populations, one on solanaceous crops and the other on a leguminous weed, were discovered in Epilachna vigintioctopunctata. On the basis of a series of experiments and field observations, it was concluded that the two types are true host races within a single species, possibly in the course of genetic divergence in sympatry.(7) Survivorship-fertility schedules of three Epilachna species were examined under the laboratory condition, and basic population parameters were calculated.(8) Seasonal change of population density in two Epilachna species was investigated at the Bogor Botanic Gardens. A preliminary analysis of the data obtained during November 1990 through October 1991 clearly demonstrated the depression of population densities during the extraordinary severe drought in July to September, 1991.