I have found that they will do this from time to time manly at night when there is no lights on. I wake up and go down stairs to see them all balled up. They will also do this if some thing has been nibbling on a stalk. I had a flame angle that decided that it liked Anitha and would thin it out a bit. Which in return made the Anitha start to multiply more. I think that during the night when this happens it could be because of the temp drop or temp difference.

Bill