Assuming the things actually discourage them from sitting on the lifelines.
Since I put these on, they don't appear to have come back. Nothing required
to hang them, just flex and slip over the lifelines. Not only do they move
in the breeze, they also slide on the lifelines in a breeze and help keep
the spider webs at bay.

http://sports.webshots.com/photo/717...31781966cIZLDB

John Cairns