The result of this study reveals that the uptake and transformation of plant natural products and volatiles constitute an important array of substances governing the sensitivity of the herbivore in food selection. Hence, an understanding of the variability of secondary metabolites and their role in insect repellence need attention in near future. The preliminary phytochemical analysis of I. carnea and V. negundo showed the presence of compounds such as phenols, saponins, xathoproteins, triterpenoids, tannins and flavonoids. The major compounds identified through GC-MS in V. negundo are 1H-indene, cyclododecanol, patchoulane, 1,2-dihexylcyclopropene-3-carboxylic acid, 2-heptenoic acid, (+) - aromadendrene, trans-caryophyllene, 7-oxabicyclo [4.1.0] heptane, cyclohexane, farnesol, pentadecane and 1-octanol. Neophyadiene, 1-decanol, tetradecanoic acid, pentadecane, 1-iodo-2-methylundecane, trans-caryophyllene, eicosane, 2-butenoic acid and cholestan-3-one are the major secondary metabolites in I. carnea. Further identification of the compounds through IR, NMR etc. is necessary to find out the exact compound responsible for insecticidal property.