Try to catch me if you can - oops maybe you can... Some keep claiming in the comments that the bugs come from the Insane AI mod... I don't care, as the bugs are just too much fun to watch!
Oh, that spot. xD I remember finding it in my first Nightmare run and being so happy the Alien couldn't get me there. Sadly, being Nightmare, it also didn't really leave me alone either...
I've always found that alien 'annoyance' animation, after you shoot it and it lowers its arms and looks right at you and screams (although here the sound effect doesn't quite line up), to be particularly creepy..
I didn't know that was a safe haven but it makes sense due to the shape of it. It may have went away if you stopped shooting and annoying it though. Might be worth a test if playing through again