Five lambs were obtained suffering from severe cutaneous perianal inflammatory lesions. Many larvae were detected between the folds of this region of diseased animals. Examination of these larvae with both light ordinary microscope and scan- electron microscope revealed that they are the third stage larvae of Chrysomia megacephala. This study is considered the first time of description of C. megacephala third stage larvae in sheep in Assiut Governorate. Different morphological features of the detected larvae were studied including anterior and posterior ends, anterior and posterior spiracles and arrangement of their papillae in addition to arrangement of the enter-segmental spines. Data which obtained by SEM about the posterior spiracles is considered of great important in helping of differentiation between myiatic larvae of sheep.