Spiders in Thief are cute and fluffy. As long as they are stationary, and positioned by a mission designer who does not know what he is doing.
Anyway. On my Ghosting-Tough through Thief Gold, I came to the infamous problem zone: The Spiders of Lost City. The spiders caused everyone to fail the ghost.
I decided to be dedicated to this task, spent a few days with it, and I finally managed to solve it. In a way that can be replicated easily, it is a way that does not require maneuvres with "1 of a million"-probabilities.
The following links lead to illustrated descriptions of the maneuvre, and to more screenshots from my Ghosting Trip (the first successful Ghost of this level ever.)