الفهرس 
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Abstract
This thesis has been undertaken with the aim of searching for naturally occurring substances from some available Egyptian plants, used as natural pesticides, especially as acaricides against Tetranychus urticae (Koch). The two spotted spider mite Tetranychus urticae (Koch) is considered as one of the most important pests causing injury to cotton, vegetable crops and fruit trees in Egypt. Three plant species were studied in details for their chemical components and also as acaricides against T. urticae. These plants are:- 1-Hyoscyamus muticus (Solanaceae) 2- Ecballium elaterium (Cucurbitaceae) 3- Schinus terebenthifolius (Anacardiaceae) Through this investigation, useful information were obtained from the application of various chromatographic methods (CC and PTLC) and spectral measurements as IR, MS, 1H-NMR, 13C-NMR, DEPT, H-HCOSY, HMQC and HMBC. Repeated chromatographic separation and structure elucidation have resulted in partial separation and identification of fifty five natural products, which could be classified into eight monoterpenoids (38-45), twenty one sesquiterpenoids (4, 5, 25, 27, 28 and 46-61), one diterpenoid (6), four alkaloids (26 and 30-32), seven shikimates (3, 15, 21-24 and 34), one flavonoid (37); three vitamins (7-9) and two miscellaneous compounds (2 and 35). from the isolated compounds one product (17) is new which has not been separated and not reported previously from any botanical source. Toxicity effect of plant extracts and their isolated compounds were studied against different developmental stages. Pet. ether extracts of E. elaterium was the most effective extract against the egg stage. While the toxicity effect of plant extracts on the larvae of T. urticae (Koch) showed that E. elaterium chloroform fraction was the most effective plant extract. The adulticidal action of plant extracts revealed that E. elaterium chloroform fraction was the most effective plant extract. In addition, repellency effect of plant extracts on adult females of T. urticae (Koch) revealed that S. terebenthifolius essential oil extract exhibited a highest degree of repellency.