Effect of Temperatures on Knockdown and Kill of Houseflies Exposed to DDT1

Abstract

Houseflies were exposed at several temps. to DDT-treated surfaces for varying lengths of time and, after exposure, held in clean untreated containers at different temps. Houseflies exposed continuously to DDT-treated surfaces were knocked down much more quickly at 70[degree] F than at higher temps. When flies were exposed for 5 or 10 min. (not long enough to cause knockdown) at 70[degree] and 95[degree] F and then held at different constant temps. for 24 hrs., very little difference in mortality occurred between flies exposed at the 2 temps. However, the flies always showed a higher mortality at the lower holding temps., irrespective of the exposure temps. Flies exposed to the residue of pyrethrum in treated cages showed a faster knockdown at 95[degree] F than at 70[degree], but a greater re-covery when held at the lower temp. Furthermore, greater 24-hr. mortality occurred when exposure was made at 95[degree] than at 70[degree], irrespective of holding temp. In all respects these results are the reverse of those obtained with DDT. These results indicate that temp. may influence the effectiveness of DDT against the same species of insect in various parts of the world.