The Emperor Dragonfly or Blue Emperor,Anax imperator, is a large and powerful species of hawker dragonfly of the family Aeshnidae, averaging 78 millimetres (3.1 in) in length. It is found mainly in Europe and nearby Africa and Asia. As it wanders widely it can also be encountered elsewhere. Males have a sky blue abdomen marked with a diagnostic black dorsal stripe and an apple green thorax. Females have a green thorax and abdomen. The male is highly territorial, and difficult to approach. The species lives by larger ponds, gravel pits, and slow rivers.