RESUMO
Immature mosquito species composition and abundance were studied in irrigated and rain-fed rice fields of North Sulawesi, Indonesia. Irrigated rice fields were characterized by the prevalence of aquatic macrophytes and cyprinodont larvivorous fish, Aplocheilus panchax (Hamilton), but abundance per dip of most aquatic insect predators was lower than that in rain-fed rice fields. Anopheles peditaeniatus (Leicester), Culex vishnui Theobald, and Culex tritaeniorhynchus Giles, were dominant in both irrigated and rain-fed fields, but the abundance of the Culex species was lower in irrigated fields. The effect of irrigation system introduction on regional mosquito abundance cannot be evaluated by the enlarged surface water area alone. Changes in habitat quality, expressed as the abundance per dip (index of density per unit water area), also need to be considered.