Oestrus ovis larvae 142 were collected from the 133 heads of sheep slaughtered at the Mosul abattoir in Nineveh governorate during March-May 2014. In This study, the weight and dimensions Oestrus ovis larvae and pupae were measured and there was a significant difference between larvae of Oestrus ovis. Forty five of the third larval stage were rearing and them pupated until emergence of the adult stage. Sixteen larvae were emerged to adult (35.6%). (4.4%) larvae did not pupariation and 60% were not reached to adult. The puparation period taking (24-30 hours) and the pupal stage taking (23-28) days the average longevity of adult flies was 10 days. This study is regarded as the first one showing that all flies were similar in their external shape and so all were belonging to Oestrus ovis causing myiasis in sheep.