We studied the population dynamics of two species of tortoise beetles, Aspidomorplw miliaris (AM) and A. sanctaecnrcis (AS) (Coleoptera: Chrysomelidae: Cassidinae), feeding on a shrubby moming gluy, Ipomoea carnea (Convolvulaceae), in Purwodadi Bounic 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 ttre 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 disappeued 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 l:l 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 ue 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 Wolda, 1988;Nakamura et al., 1990; Inoue et ql., 1993 (Nakamura & Abbas, 1987ab, 1989 Nakamura et al., 1989). We compare our results with those in former studies, illustrating how insects adapt thefu life history to different habitat conditions in the tropics.We previously reported how seasonality affects abundance and egg mortality (Nakamura & Abbas, 1987ab, 1989, survivorship and fertility schedules ofAM and AS under laboratory conditions in padang (Nakamura et al., 1989), the effects of ants on larvae of AS in Bogor (Noerdjito et al., 1992), and a list with keys to genera and species of Cassidinae of Java, including AM and AS (Kimoto aal.,1996). padang lies on the equator (0"53'5, 1.00'21'E, near sea level), and has a predominantly tropical rainforest climate with an annual rainfall of 4000-5000 mm without a distinct alternation of dry and wet seasons (Inoue & Nakamura, 1990). Bogor (6'37'5, 106"32'E,260 m altitude), located at the eastern end of the tropical rainforest climate centered by Padang, has an annual rainfall of 3850 mm (range = 2000 to 55ffi mm). In Bogor, the cycles of dry and wet seasons are less distinct and more irregular than those of East Java, where the present study was conducted' Compared with Padang' Bogor has lower but more seasonal rainfall and more severe droughts'The present paper addre...