Not enough "Bugs" in your game?
UniBug is a simple to use but powerful system to create flies, bees, dragonflies, butterflies and ladybugs in your gamewith realistic motions.
All types of bugs will fly around in your scene. Bees, fliesand ladybugs are also able to land on the ground and movearound.
There are several ways to define the "bug-zones".This system is designed for plane undergrounds and not allfeatures will work perfectly with the Unity-Terrain.A Manual can also be found in the package.
Now approved for Unity 4.x
Also have a look at the example
video.