The Joint Action of DDT and Ethyl Alcohol upon Anopheline Larvae in Bioassay Suspensions1

Abstract

The concentration of the initial DDT solvent (ethyl alcohol) affected the kill of anopheline larvae in bioassay suspensions prepared by the replacement of solvent method. In 3 series of suspensions containing 1, 0.1 and 0.01% ethanol, but identical amounts of DDT, the LD50 doubled with each decrease in concentration. The LDgn for the 1 and 0.1% series were equal, but doubled in the 0.01% series. Two series of suspensions prepared by diluting with water 2 stock DDT suspensions produced lower kills than were expected on the basis of ethanol content, indicating that in some way the method of suspension preparation also plays a role in larval kill. Larvae conditioned in a 2% ethanol solution prior to their introduction into the DDT suspensions were more readily killed than unconditioned larvae.