Samples of ground beetles (Carabidae) were collected throughout the year-long 1985 Joint Indonesian–Royal Entomological Society expedition, Project Wallace, in an area of rain forest in N. Sulawesi. The beetles were collected by a range of collecting techniques including insecticide fogging, malaise, flight interception, pitfall and light trapping as well as hand collecting. The state of ovary maturation was determined by dissecting the females. A high number of species of Carabidae show a distinct seasonal reproductive rhythm in the form of gonad dormancy, avoiding reproduction in the slightly cooler months in the middle of the year. In contrast, most species of tiger beetles (subfamily Cicindelinae) are reproductively active at this time of year. The study area appears to have an unusually variable monthly rainfall for this region, and we suggest that the seasonality in the ground and tiger beetles is a response to the strict annual rainfall patterns of the coastal areas 10–20 km to the north and south.