Use of a funnel trap for collecting immature Aedes aegypti and copepods from deep wells in Yogyakarta, Indonesia

During the course of a "dry" season dengue vector survey, indoor and outdoo r household wells were sampled for the possible presence of immature mosqui toes and copepods. With a simple floating funnel trap, Aedes aegypti immatu re stages were captured in over 33% of the sampled wells (n = 93) during a 24-h trapping period per well. Average number of larvae tall instars) per p ositive well was 8.8 (range 1-63). Positive wells varied in depth from 2.7 to 14.7 m (8.8-48.2 ft), with a mean of 7.9 +/-SE 0.5 m in well rim to wate r surface. Only 4 wells (4.3%) contained Culex quinquefasciatus larvae. Onl y I of 31 infested wells contained both species. Aedes albopictus was not d etected in any of the wells. Cyclopoid copepods were captured in 15% of the wells. No significant difference was found between positive and negative w ells with regard to the physical characteristics (inside diameter, distance to water level! or the depth and volume of water held at the time of sampl ing. A significant association was found between wells positive for larvae and numbers of other positive containers in the vicinity of the wells, In g eneral, wells containing copepods had fewer larvae present in the trap, pos sibly indicating some level of natural population regulation of Ae. aegypti occurring in the well; however this association was not significant. Preli minary results indicate that a ells in Yogyakarta serve as important perman ent habitats for Ae. aegypti, especially during the dry season.