The usual methods of studying the ovipositional attractants of Aedes aegypti (L.) in the laboratory have consisted of giving gravid females a choice between 2 or more sites for egg deposition. This approach has been employed to determine the role of many physical, chemical and biological factors as ovipositional attractants. Light intensity, water surface reflectance and surface texture influence site selection of Ae. aegypti (Wood, 1961, Bull. Entomol. Res. 53 : 541–60; OʼGower, 1957, Proc. Linn. Soc. N.S.W. 82 : 240–44; Snow, 1971, Bull. Entomol. Res. 60 : 683–96). Results of studies of Hudson (1956, J. Exp. Biol. 33 : 478–92), Pillai & Madhukar (1969, Curr. Sci. 5 : 114–16) and Sehgal & Pillai (1970, Bull. World Health Organ. 42 : 647–50) indicate no attraction to inorganic compounds. In contrast, several organic compounds produce a positive response in ovipositing Ae. aegypti (Perry & Fay, 1967, Mosq. News 27 : 175–83; Pillai & Madhukar, 1969, loc. cit.). Since bacteria are important to the nutrition of Ae. aegypti larvae (Rozeboom, 1934, Am. J. Hyg. 21 : 167–79), it is reasonable that microbes or microbial metabolites influence site selection for egg-laying. This seems indicated by the findings of OʼGower (1957, loc. cit.), Gjullen & Johnsen (1965, Mosq. News 25 : 14–15) and Hazard et al. (1967, Mosq. News 27 : 133–36) which have shown that different infusions containing organic matter attract ovipositing Ae. aegypti .