The Harpy is a changed female being mutated after inhaling the black spores produced from the Mortifilia's flowers.
This mutation affects the subject in a great manner, her skin becomes grey-ish, her arms are cut away, her face is covered with some kind of roots, looking like hair, and most important, her stomach, pelvis and part of her legs are opened forming some kind of mouth.
They generally move in pairs or in groups and attack exploiting their ability to float in the air. Graceful and agile, the Harpy attack from surprise and emitting sounds similar to female moans. The inside of their legs spread stings that these creatures use to attack striking with kicks and, soon after, they give a boost to the body of the enemy to get away from a possible counteroffensive.
If unknown how it has the ability to fly. It could be that it has some sort of invisible wings or the Mortifilia makes them float.
Although they attack in large groups and easily avoid attacks by moving through the air, the Harpy does not possess great physical strength and are easily overpassed with a few strokes of a melee weapons.
Wasting ammunition against these monsters is only good when you are cornered, but in general, you can get the better of them throwing them to the ground with the Stun Gun and then using melee weapons to finish them.
Alternatively you can try to hit as soon as they come close to attack, to prevent them from inflicting damage to yourself.