Straw Infusion Attractiveness to Gravid Female Culex salinarius1

Abstract

Results of replicated field-plot studies and observations at Bombay Hook Refuge. Del., from 1959 to 1964 indicated that certain chemical factors of apparent protein origin are responsible for the pronounced attractiveness of straw infusion to gravid females of Culex salinarius Coquillett. Physical factors such as cover or shelter proved less significant. These chemical attractant substances were isolated by treating concentrated straw infusion with 10% trichloracetic acid. Subsequently, water suspensions of the acid-free residues were field tested against straw infusion, natural habitat, and tap water. Field observations and experimental data showed that the trichloracetic acid extract actively attracted more ovipositing females of C. salinarius than did the straw infusion, whereas natural habitat and tap water attracted relatively insignificant numbers. These findings suggest the means by which mosquito oviposition site selection takes place and provide a basis for understanding the ecological distribution of larvae. Although further chemical definition of the attractant substance is needed before it can have practical application, the results of this work may lead to the development of an oviposition “lurc” applicable to highly selective control measures.