LE How do you get insects to appear in your game?

[kibblesticks]

I tried searching for this but couldn't find an answer. How do people get insects, such as butterflys and bees, to appear? I place the critter spawn orb thing in the CK, but when I go in game the insects aren't there (or rather, they are there but they fade after about 2 seconds). I've Navmeshed a little bit around the area around where they're supposed to spawn, do I just need to give them a larger Navmeshed area? Or am I missing something crucial? Any help very much appreciated