Effect of Short Contact with DDT Residues on Anopheles gambiae1

Abstract

Female A. gambiae allowed 60-, 30-second and 5-second contacts in an aspirator tube coated with residues equal to a dosage of 125 mg. of DDT per sq. ft. showed typical DDT-toxicity in 95% mortality 8 hrs. after contact. The 60-sec. group gave 100% mortality 9 hrs. after contact and the 30-sec. group gave 100% mortality between 10 and 24 hrs. after contact. Those mosquitoes allowed 5-sec. contacts gave 97% mortality between 10 and 24 hrs. after contact. The aspirator tube method was adequate to test actual contact time in contrast to the cage method where the mosquitoes fly about a good deal of the time and thus negate attempts to estimate actual length of contact with the insecticide.