The insecticide-resistance problem: a review of developments in 1956 and 1957.

The author reviews the growth of the insecticide-resistance problem throughout the world during the period between July 1956 and November 1957, and the developments in research on the subject during the same period.Three new resistant species have been discovered-Anopheles subpictus, Chrysomyia putoria and Rhipicephalus sanguineus-and eight new types of resistance in already resistant species have been observed. Moreover, the geographical area covered by certain resistant insect populations has considerably increased.THE RESEARCH ACCOMPLISHMENTS DURING THE PERIOD UNDER REVIEW INCLUDE: systems of detecting resistance in the field by standard test methods; confirmation of two distinct types of resistance to chlorinated-hydrocarbon insecticides in mosquitos and bed-bugs as well as in houseflies; evidence that DDT-resistance in the housefly, Anopheles sundaicus and Aëdes aegypti is due mainly to a single genetic factor associated with the ability to dehydrochlorinate DDT, and that dieldrin-resistance of Anopheles gambiae also derives from a single factor present even in untouched populations; a fuller understanding of the physiological mechanism of BHC-resistance in the housefly; and demonstration that selection pressure from organo-phosphorus compounds induces resistance to themselves and to chlorinated-hydrocarbon insecticides.