Polymorphism larval stages of Oestrus ovis isolated from frontal sinuses and horn cavities of sheep’s head Slay in Basrah abattoir

The study include isolated larvae of Oestrus ovis of diptera from frontal sinuses and horncavities of sloughted sheep heads. It could be differentiation from another species of Dipterawhich cause myiasis by some characters. Three stages of the larvae were isolated. In generallythe larva stages contain eleven segment, cephalopharngeal skeleton connect with two hooks. Thecharacteristic of L1 stage were white in color, measured L1(3-4mm) in length ,have not spinesand structure of posterior spiracular have D shape & yellow in color whereas internally smallstructure like D shape was present with brown color and the pits or pores occur in whole structure. The L2 stages are slightly grey in color ,measurement was (6-12mm ). In contrast the L3( 20-19mm), with grey to brown in color and have plate dark brown to black color on dorsal surface.posterior spiracular of L2 & L3 stages have D shape and brown in colors with many spreadpores, the ventral surface tegument contain three arrows of spines. Third instar larvae aredeveloped and become pupate during 6- 12 hours out of animal body