Malathion Resistance Studies on the House Fly

Malathion resistance in house fly ( Musca domestica L.) strains from Phoenix, Arizona, and Savannah, Georgia, was confirmed in laboratory tests during the fall of 1956 Physiological resistance was shown using exposures to malathion-sugar residual applications and topical applications of malathion-acetone solutions. Using colony cages with 5, 25, and 45% of the available resting surface treated with malathion-sugar residual deposits, strains with higher levels of resistance were selected from the resistant filed strain. The physiologically resistant strains also showed a correlated behavioristic resistance in their avoidance of malathion bait but not of Dipterex baits. Comparison of resistance levels of 1-, 3-, and 5-day-old adult males and females showed a marked inverse relationship of age to resistance.