Egypt. J. Exp. Biol. (Zool.), 8(2): 363 – 375 (2012) © The Egyptian Society of Experimental Biology ISSN: 2090 - 0511 On Line ISSN: 2090 - 0503 http://www.egyseb.org RESEARCH ARTICLE Wafaa A. Radwan Nadia Helmy* Dalia, A.M. Salem* Reda F.A. Bakr* & ** Noha A. Guneidy* Shimaa S. Mohammed* ULTRASTRUCTURE CHANGES INDUCED BY CHITIN SYNTHESIS INHIBITOR AND EXTRACT OF RICE BRAN IN EMBRYOGENESIS OF THE HOUSE FLY MUSCA DOMESTICA LINNAEUS ABSTRACT: Ultrastructure study, using semi-thin sections and electron micrographs, was carried out to demonstrate the ovicidal effect of chitin synthesis inhibitor (Lufenuron) and acetonic extract of rice bran, Oryza sativa on embryogenesis of the house fly Musca domestica . For this purpose the embryonic development of the normal house fly eggs was studied using ultrastructure technique during cleavage, blastoderm and gastrulation. Cleavage started 15 minutes postoviposition (POP) and continue to divide until cellular blastoderm is formed 2 hours later. After 3 hours, the germ band is formed, differentiated into ectoderm and mesoderm. At 4 hours, while the embryonic envelopes are formed, gastrulation of the germ band takes place. Ultrastructure study revealed that application of both compounds to newly Musca domestica laid eggs (0-15 minutes) blocked the embryonic development at cleavage stage and before the blastoderm and pole cells formation. Extensive cellular and tissue damage of the developing embryo was observed. KEY WORDS: Musca domestica, chitin synthesis inhibitor (Lufenuron), plant extract, rice bran ( Oryza sativa), embryogenesis, ultrastructure CORRESPONDENCE: Wafaa Ahmed Radwan* Department of Entomology, Faculty of Science, Ain Shams University, Cairo, Egypt E-mail: dalia.salem@email.com Nadia Helmy* Dalia, A.M. Salem* Reda F.A. Bakr* & ** Noha A. Guneidy* Shimaa S. Mohammed* * Department of Entomology, Faculty of Science, Ain Shams University, Cairo, Egypt ** Biology Department, Faculty of Science, King Khaled University, Abha, Saudi Arabia ARTICLE CODE: 47.01.12 INTRODUCTION: Chemical insecticides are currently one of the main methods used for house fly control. However, the serious health and ecological disadvantage of this method are well known, therefore it is clear that there is an urgent need for alternative control measures, which must be active against the pest, safe to humans, and environmentally friendly. One promising way to fulfil this need is through the use of insect growth regulators (IGRs). Chitin synthesis inhibitors (CSI) is one of the main groups of IGRs which interfere with cuticle formation (Ishaaya and Casida, 1974; Post et al ., 1974). Among the diverse in vivo actions of CSIs on the life cycles of pest insects of various orders are ovicidal and larvicidal effects (Ascher et al. , 1987; Sáenz-de-Cabezón et al., 2006; Belinato et al., 2009). Lufenuron is a novel CSI belongs to the benzoyl phenyl ureas (BPUs) group. It is known to act as an active ovicide with a broad spectrum activity in various insects including Lepidoptera and Diptera (Wilson and Cryan, 1997; Sáenz-de-Cabezón et al ., 2006). Lufenuron has very low toxicity to mammals and is non toxic to birds. The