Dragonflies are passive insects that spawn in the swamp biomes. Along with all the other insects that live there, they add a very nice atmosphere to the swamp, due to their fast flight.
Dragonflies have 2 hearts. Similar to butterflies and moths, they are aerial insects, and will always fly above the ground. Even though they do not react to the player in any way, they are hard to hit, due to their constant flying and tremendous speed.