Random Raids?

[tnbp]

I need someone to help me understand the base raiding mechanics.  I have been seemingly randomly raided three times now.  There has not been a visual warning that things are amping up (i.e., "Larva want you gone.")  On top of that, I have killed literally zero bugs leading up to them, either.  There's not a meter or something that I don't know about where I can see how pissed a faction is/is getting, right?  I don't want to turn raids off-- but I'd like to understand what is happening, here.  Was something added in the most recent patch?  I've never experienced this prior to very recently.  I just don't get this.  Is anyone else experiencing this, as well?

[tnbp]

I've been raided many more times in the same fashion since my original post.  It seems like it always happens right as I wake up from sleeping overnight.  I'll wake up in the morning, I hear the horn sound, and then a raid starts.  I really don't understand.  Who can explain the raid mechanic to me?

[Creepercharge56]

I think the larva only randomly raid you if you build defences like walls and you stay at your base for a long time.