Insecticide-induced behavioral responses of Anopheles minimus, a malaria vector in Thailand

This study was designed to determine the behavioral responses of 2 test pop ulations of Anopheles minimus females to DDT at 2 g/m(2), deltamethrin at 0 .0625 g/m(2), and lambdacyhalothrin at 0.0369 g/m(2) using an improved exci te-repellency escape chamber. One test population was colonized in 1993 and referred to as a young colony. The 2nd field test population was collected from Ta-Soa County, Tri-Yok District, Kanchanaburi Province, in western Th ailand and referred to as a wild population. Results showed that females of both young and wild test populations rapidly escaped from direct contact w ith DDT, deltamethrin, and lambdacyhalothrin. Lambdacyhalothrin exhibited t he strongest irritant effect on female mosquitoes, followed by DDT and delt amethrin. Fewer females escaped from test chambers without direct contact w ith treated surfaces but the response was significantly different from that of the controls (P < 0.05). The noncontact response is indicative of a non contact repellent action. Both contact irritancy and noncontact repellency are involved in An. minimus escape responses. Experimental hut studies that include monitoring of house-entering populations of An. minimus are needed for a meaningful assessment of noncontact repellent actions.