249 - 251 A comparative study

Adult mosquito collections were conducted for 12 weeks in two residential areas in Kuala Lumpur. The CDC light traps were compared using dry ice and yeast as sources of carbon dioxide attractants for mosquitoes. The efficacy of the dry ice baited trap was significant over yeast generated CO2 trap. The predominant species obtained were Culex quinquefasciatus, Stegomyia albopicta and Armigeres subalbatus. Researchers have used CDC light traps to sample mosquito populations for many years (Service, 1976). However, it has been found that light traps on their own are not very attractive to mosquitoes (Vythilingam et al., 1992). Most often the light traps are augmented with carbon dioxide from dry ice. However, in some remote areas where it is difficult to obtain dry ice one is hampered in the collection of mosquitoes using CDC light traps. In a recent study in Japan Saitoh et al. (2004) evaluated the efficacy of yeast generated CO2 as an attractant for mosquitoes in field collections by using yeast which converts sugar into CO2 and ethyl alcohol. Thus the objective of this study was to compare the efficacy of CDC light traps using CO2 from two different sources. Two sites were selected in Kuala Lumpur and mosquito trapping was conducted from June to August 2005. Federal Hill is an upper middle class residential area situated in the heart of Kuala Lumpur. It is surrounded by forest. The second site was 3 km away from the Institute of Medical Research which houses the staff quarters. Four traps were operated in each area from 1800 hours each night to 0600 hours the following morning. In each area two CDC light traps were augmented with dry ice (Vythilingam et al., 1992) while another two used CO2 generated from yeast mixture. A five liter plastic bottle contained the mixture of 18 gm yeast (Saccharomyces cerevisaie), 250 gm of sugar and 3250 ml of water. The five L bottle was connected to a 500 ml bottle with tubes. The smaller volume bottle was used to hold the overflow water solution. CO2 generated was released from a 5mm hole on the side of the 500 ml bottle. A rubber tube was connected from the bottle and placed near the CDC light trap entrance. The yeast mixture was prepared five hours prior to setting up the traps. The four traps were arranged in a quadrate and the position of the two sources of CO2 was rotated for each collection. Distance between the traps varied between 1.7 m to 5m on different collection days.