Vires

Vires is a bat like creature that can be found in the Underworld and caves throughout Hyrule. Certain Vires split into two Keese when attack, or others can turn into Keese at will. The best defense against them it to use your Boomerang (Z1) to stun them and attack. Or (Z2) wait for them to land and attack then.

Zelda 1, 2