Population Dynamics of a Phytophagous Lady-beetle, Epilachna vigintioctopunctata (FABRICIUS) (Coleoptera: Coccinellidae), Living in Spatio-temporally Heterogeneous Habitats II. Seasonal Changes in Adult Movement and Spatial Distribution of the Population

Abstract

The population process of the phytophagous lady beetle, Epilachna vigintioctopunctata, was studied in spatio-temporally heterogeneous habitats in order to clarify the seasonal changes in interpatch movement of adults, density effect on the movement, and the effect of the movement on the spatial distributions of the population. The population censuses were carried out for three years in an area of about 15 ha containing 18 distinguishable patches of host plants. The rate of interpatch movement of females tended to be highest in the first generation adults, moderate in the second generation adults, and lowest in the overwintered adults. The movement rate of females tended to increase incrementally with adult density. This density-dependent interpatch movement of females which accompanied mortality in the dispersal process reduced the patch variation in the densities of females and eggs, and was thought to be the most important foctor in stabilizing the yearly fluctuation of population density. © 1993, JAPANESE SOCIETY OF APPLIED ENTOMOLOGY AND ZOOLOGY. All rights reserved.