491 Med. Fac. Landbouww. Univ. Gent, Belgium. 66/2a: 491-502. Respiratory metabolic responsiveness, during the pupal stage, of the red palm weevil, Rhynchophorus ferrugineus (Coleoptera: Curculionidae) to certain plant extracts. Bream, A.S. * ; Ghoneim, K.S. * Tanani, M.A. * and Nassar, M.M. ** * Faculty of Science, Al-Azhar University, ** Faculty of Science, Cairo University, Madinet Nasr, Cairo, Egypt. KEYWORDS: Rhynchophorus ferrugineus, Azadirachtin, Jojoba oil, respiration rate, CO 2 - output, respiratory metabolism, respiratory quotient, pupal stage. ABSTRACT the prepupae of Rhynchophorus ferrugineous were topically applied with one of three dose-levels (0.1, 0.005 or 0.001 µg/insect) of Jojoba oil o Azadirachtin. The daily O 2 consumption and CO 2 out put respiratory were determined and the respiratory quotient (RQ) was calculated. After Joj treatments, O 2 consumption of early- and late-aged pupae increased as the dose-level was decreased. The respiration curve did not assume an U-shaped pattern as common in the pupal stage of many insect species. Also, an inhibitory action of Azt on the pupal respiration had been clearly exhibited. A similar result of the respiration curve was observed by Azt. All dose levels of Joj, but only the higher two ones of Azt, suppressed the CO 2 release. Both botanicals inhibited the RQ during the pupal stage. However, all RQ mean values of treated, or control, pupae were < 1.0 and > 0.7. INTRODUCTION Needless to say the extensive use of synthetic insecticide leads to the destruction of beneficial species such as parasites and predators of pests beside the destruction of pollinating insects such as honeybees. Also, the wide use of insecticides had some undesirable consequences such as the development of resistant strains of many pests and the growing toxic hazards to man, his livestock and wild life. Insect growth regulators (IGRs) cause inhibition of insect metamorphosis, reproduction and embryogenesis as well as disturb their diapause. Since plants had been discovered as a rich resource of IGRs, researchers allover the world gave their attention and interest for extraction, isolation and bioassay of extracts from many plant species against different insect species (Slama et al.,1968; Schwarz et al., 1971, 1974; El-Zoghby, 1980; El-Shazly et al., 1997; 1997; Khalaf, 1998). Azadirachtin is a seed kernel extract of neem Azadirachta indica ( Meliaceae) which was tested against many insects species as antifeedant or/and growth inhibitors (Redfern et al., 1981; Jacobson, 1986). The present study extends our previous works (Bream et al., 2001; Ghoneim et al., 2001 a,b) about several biological and physiological aspects of the red palm weevil Rhynchophorus ferrugineus which was reported as dangerous pest for date palm in Arab Gulf region at the mid-1980s (El-Ezaby, 1997) and then in Egypt at 1992 (Cox,1993; Murphy and Briscoe, 1999). The purpose of this paper was to assess the effects of Azadirachtin and Jojoba on the respiratory metabolism during the pupal stage of the present experimental insect.