DEMOGRAPHIC ATTRIBUTES OF AN INTRODUCED HERBIVOROUS LADY BEETLE

Demographic attributes of the adults of an introduced herbivorous lady beetle Epilachna niponica (Coleoptera: Coccinellidae) were investigat ed from 1975 to 1981 in the Botanical Garden of Kyoto University. Popu lation growth rate varied from 4.8 to 16.8 throughout the study period . Fecundity and mortality in the late larval period contributed most t o annual changes in the population growth rate. Population growth rate was negatively correlated with the density of overwintering adults. A dult survival from emergence to the reproductive season, which varied from 0.03 to 0.36 throughout the study, was almost completely determin ed by survival during the pre-hibernation period. Adult survival to th e reproductive season changed in a size- and sex-dependent manner. Lar ger adults survived better than smaller individuals; male-biased morta lity occurred from adult emergence to the reproductive age. Severe int raspecific competition among late instar larvae due to host plant defo liation produced a higher proportion of small-sized adults, resulting in lower adult survival to hibernation. The introduced population had a higher population growth rate and a lower adult survival to the repr oductive season than the source population.