Abstract
We studied the population dynamics of two species of tortoise beetles, Aspidomorpha miliaris (AM) and A. sanctaecrucis (AS) (Coleoptera: Chrysomelidae: Cassidinae), feeding on a shrubby morning glory, Ipomoea carnea (Convolvulaceae), in Purwodadi Botanic Garden, East Java, Indonesia. Rainfall in Purwodadi is distinctly seasonal with 5-7 months of harsh dry season, lasting from March or April to October or November. In March of 1993, we established three study sites by planting 10 cuttings of the host plants on each site. We carried out a weekly census including mark-recapture of adults with color paints and construction of life tables for immature stages, from June 1993 to March 1996. Total number of leaves on the study sites increased during the wet season and decreased during the dry season, although effects of dry seasons on the change in the total number of plant leaves depended on the site condition (sunshine and water). We marked all beetles found on the sites (136 and 436 beetles for AM and AS, respectively). Adult populations of the two species increased in the rainy season, decreased as the dry season started, and disappeared in the late dry season. Seasonal trends in the adult numbers mainly reflected the oviposition activity of adults, which was high in the rainy season and diminished or nil in the dry season. The sex ratio was 1:1 in AM and largely female-biased in AS. Average adult residence time (days) on each site was 6.6 (male) and 8.1 (female) in AM and 7.0 (male) and 9.8 (female) in AS. The current results are discussed with our previous data of the two species in two localities with higher and less seasonal rainfall conditions, Padang (central Sumatra) and Bogor (West Java).
