Comparative toxicity of some synthetic insecticides,and a growth inhibitor,in the migratory locust,Locusta migratoria

1. The comparative toxicity of four synthetic insecticides (Dieldrin, Methomyl, Fenitrothion and Permethrin) in the different developmental stages of the migratory locust shows that resistance tends to increase with the developmental larval stages except in the adults which show lower resistance than the fifth larval stage.2. The resistance to a growth inhibitor, Teflubenzuron in the different developmental stages shows the reverse phenomenon—the younger larvae were more resistant than the fourth and fifth larval stages while the adults were almost not affected by this product.3. A comparison of the toxicity of the synthetic insecticides in the two forms of the insect, the solitarious and the gregarious, shows that the solitary insects were more resistant than the gregarious ones.