The relationship between contact chemoreceptors and landing of female moths in the field to find out a suitable place for egg laying is very important to discover a suitable places for the immature and adults to complete their development. Chemoreceptors play an important role in mediating a diverse range of behaviours, including avoidance. The present research has been conducted to evaluate the activity of extracts from seeds and leaves of Ricinus communis against oviposition of Spodoptera littoralis. Four solvents with different polarity (petroleum ether, chloroform, ethanol, and water) were used to extract the plant material. Results showed that the fixed oil of petroleum ether and chloroform extracts from seeds were more effective in inhibiting oviposition activity than water extract. Water and alcohol extract was most effective than leafs volatile oil as inhibiting oviposition (eggs/♀). On the other hand, macerated Nerium oleander and the females produced the highest number of egg masses as compared to stimulated oviposition. Electrophysiological studies revealed that the chemosensitive sensilla on antenna and tarsus were sensitive to all tested extracts. The results indicated that both the frequency and the amplitude of afferents from sensilla differed according to the type and concentrations of the extract. In general, the biological activity of R. communis extracts was solvent type-and concentration-dependent.
Key words: Spodoptera littoralis, castor oil, contact chemoreceptors, oviposition deterrence, oviposition behaviour