The Spider That Spins Wood
A spider has been discovered by humans that spins a wood like substance instead of silk or thread.
This spider also has a unique method of catching it's prey/it's food, by sawing off little bits of it's web, akin to loosening the steps of a ladder. So when a fly lands, they think it's all perfectly solid, clearly in order and fair game. And the really interesting part is when the fly steps on one of the 'faulty' bits. They just slip through and fall to the ground, as though the floor or air has been removed from under them. They do not as you would expect fly away.
Theories so far suggest it is because it is a truly alien experience for these tiny creatures, as they have been far too light to break any known wood or branch that they may have landed on in the long history of their existence. The shock therefore, allows for this fall. And on the ground, the collision offers an opening for the trap setter to slink down and collect it's bounty.