It's just annoying to see them fly in and out of walls...

If you are talking about critter spawns - bugs & etc. You can shorten their radius in one of the properties or tabs.
You could also try putting collision planes up.

That said, I just rejoice if I see them doing anything. Most of the time it looks like their spawn conditions are not being met and I don't see any of them.

Funny when a 4000 lb torch bug flies into a silver jug and knocks it off a table.

Have you had any luck with a collision plane? I tried doing that but couldn't find a type that actually stopped them, they flew through every one I tried and I tried most of them.

I've never really had any issues with critter spawns luckily since my dungeon is dark.

Also, do collision planes work on critters?

I don't think collisions planes will work on bird/bug Critters because they are Activators being translated, not Actors running an AI package. TranslateTo and its related functions ignore collisions.

Okay, that was my experience too... for those "bugs in a jar", they must do what shalani suggested and lower their radius.