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 EI Niiio, and the degree of synchronization in the trends of the populations among the adjacent study sites.
The oviposition patterns of seven "Epilachna ", one Afidenta and three "Henosepilachna" species from Indonesia and Japan were examined and compared with those of 10 Asian species of epilachnines previously documented. The 21 species were divided into two groups based on the patterns. The first group consisted of twelve "Henosepilachna" species and Afidenta misera, and the other one consisted of eight "Epilachna" species. The former group laid several to dozens of eggs in an erect position and in mass on the underside of host leaves. On the other hand, the oviposition pattern of the latter group was diverse. They laid eggs singly, or up to ten plus eggs together, on the leaf surface or in tendrils of host plants. Eggs were usually not erect, but flat on host leaves, or were attached to or inserted into tendrils. The possible relevance between the oviposition patterns and the abundance of epilachnine species in the field was briefly discussed.
Reproductive isolation in four Sumatran Epilachna species was studied by testing 1) food preference, 2) mate choice, 3) sperm viability and 4) hybrid viability.Food habits of two solanum feeders, E. vigintioctopunctata and E. enneasticta (abbreviated as Ev, Ee) overlapped, while two cucurbit feeders, E. dodecastigma and E. septima (Ed and Es) preferred different food plants. Complete or strong ethological isolation was observed in all but one combination consisting of Ev and Es females and Es males. In this combination, half of the Ev females and all Es females received sperm of Es male(s), but sperm of Es male(s) was inactivated in Ev females. The average percentage of egg hatch for four conspecific combinations was 65.9%, while in 12 interspecific ones none hatched. These results show that the four Epilachna species are completely isolated by the combination of 1) difference of food preference, 2) strong preferences for conspecific matings, 3) inactivation of sperm in heterospecific females, and 4) inviability of eggs from interspecific matings.Food plants of Ev, Ee, and Es were introduced to Sumatra relatively recently and the presumed native food plants of these three species have not been found. Thus, the four Epilachna species had probably been isolated when the present relationship between Epilachna and their food plants was established in West Sumatra.
A non-pest Sumatran phytophagous lady beetle, Epilachna pytho was reared under laboratory conditions to study survivorship and fertility schedules. enneasticta, a non-pest species feeding on Solanaceae and living in high lands. E. pytho exhibited 1) longer immature stages, 2) longer mean length of the pre-reproductive period, 3) lesser fertility and 4) smaller r and larger T values than four pest epilachnine species, living at a wide elevational range.Key words: Coccinellidae / Epilachna pytho / phytophagous lady beetle / survivorship and fertility schedules / West SumatraIn our previous articles, we reported the survivorship and fertility schedules of five species of phytophagous lady beetles (subfamily Epilachninae) from Sumatra and Java, Indonesia (Nakamura et at., 1984 for Epitachna septima and E. pusillanima, previously treated as E. dodecastigma, cf. Booth
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