In the Forest biome, there is a chance you may encounter a Bee Hive
A bee will spawn every fourth time the hive is hit. The third round of hitting will spawn a large number if bees, but it will also leave the hive destroyed.
When the mass wave comes out of the hive, they mostly stay in one condensed group. You can hit most of them at once. Use the same tactic as you would for a single bee.
A easy tactic to Avoid battle is to acquire the Thunder Staff (Or Thunderbrand) and Constantly use it above it on a Platform, Causing them to bunch up in attempt to kill you, getting rid of them effectively.