Plant derived insecticides as compared to synthetic ones are safer for the environment, generally cost effective, easy to handle and used by small industries and farmers. an experiment was conducted on Hamedan Agricultural Research Center, as factorial based on completely randomized blocks in 3 replications in 2009 during. Experimental treatments included 6 levels with concentration (0, 0.25,0. 50,0.75,10,20,30) mg/cm2 as the time at 3 levels (8,24,48) hours as the second factor. 1 ml of each solution were applied on filter papers (Whatman No. 1). Then each dried paper was placed at the bottom of a Petri dish (5.5 cm X 1.2 cm) and 10 adults each of C. maculatus was placed in each Petri dish and covered with a lid. Controls received only water alone. Each set of treatment was repeated 3 times and number of dead insects in each petri-dish was counted at an interval of 8, 24, 48 hour respectively. Percentage mortality was calculated formula. The findings of contact toxicity unveiled that the mode of action of essential oil and its components against adults of C. maculatus was dosage and exposure time dependent. It has been noticed that the Thymu vulgaris essential oil showed 56% mortality adult C. maculatus at a dose of 0.25 mg/cm2 respectively. Further increase the concentration of oil to 30 mg/cm2 , yielded higher mortality of 98% against adult C. maculatus. No mortality was obtained in the control within the same time period.