A field trial was laid out with eight insecticides on groundnut at Padappai in Tamil Nadu. Toxicity of these insecticides to the first and third instar larvae ofSpodoptera liturawas evaluated as (i) immediate toxicity on the basis of mortality of larvae in 24 hours on groundnut leaves carrying fresh dry film of insecticide and (ii) residual toxicity by comparing the mortality data of the larvae released on 1, 2, 4, 5, 7, 8, 9 and 11 days old residues. Cypermethrin was found superior in both aspects against the two instars of S.liturafollowed closely by deltamethrin and fenvalerate. Endosulfan and triazophos were more effective against first instar larvae compared to the third instar larvae. The order of toxicity based on LT50values estimated for the third instar larvae was cypermethrin > deltamethrin > fenvalerate > endosulfan > triazophos > quinalphos > carbaryl > phosalone.