Are you playing your favourite mod-pack, like Stone Block or Stone Block 3 ?
Are you fed up with living in a cave full of Bats ?
The Bat Box will stop bats spawning within a given area. It will kill existing bats when the block is placed
Note: it does not actively kill bats that fly into the given area - its made like this so as not to tick the server
The Bat Charm will actively kill bats within an area around the player
Configs:
Named bats will not be affected by the Bat Box or Bat Charm
Default area is 128 blocks