Results of fenitrothion selection of Culex pipiens fatigans Wied. and Anopheles albimanus Wied.

Laboratory selection of Culex pipiens fatigans (=C. quinquefasciatus) and Anopheles albimanus by fenitrothion pressure for 30 and 25 generations, respectively, resulted in only 2.2-fold and 1.1-fold increases in tolerance to this compound. Cross-resistance to arprocarb in Culex increased 12.2-fold but smaller increases in tolerance to fenthion, malathion, DDT, and dieldrin, may be manifestations of vigour tolerance. Since the essential conditions for selection are believed to have been fulfilled, the authors consider the negative results obtained to be of practical significance, as well as of academic interest.