Abstract
Relative toxicity of 14 insecticides was examined by the topical application. Test animals were two rice pests : Nephotettix cincticeps and Chilo suppressalis, and their predators : Lycosa pseudoannulata and Conocephalus maculatus. The relative toxicity of insecticides was expressed in terms of the ratio of LD50 of predators/LD50 of insect pests. Among four carbamates, carbaryl was least toxic to L. pseudoannulata and C. maculatus. Of the organophosphates used, fenitrothion, pyridafention and tetrachlorvinphos were less toxic to L. pseudoannulata but were highly toxic to C. maculatus. C. maculatus, however, was very susceptible to six organophosphates. The toxicity of chlorophenamidine to L. pseudoannulata was as high as carbamates but was low to C. maculatus. The acute toxicity of cartap to L. pseudoannulata was low, i.e., 102.6 μg/g(LD50 after 24 hr), but all spiders were paralysed as low as at 10 μg/g and their recovery was postponed 8 days. The toxity of γ-BHC and methomyl to both species of predators were high : the values of the relative toxicity were far less than unity.
