They are made for stealth, and as such in the evening they are almost invisible to the eye. Complex, and geometric in pattern, they are constructed to be instruments of bondage and death. The spider after it makes it's trap hides inside this vortex. With the movement of the web, it moves quickly to the prey. The once hidden spider is then seen.
Death happens quickly.
Terrorism makes its own web. But notice in that verse there is hope. It appears that there are some things that a spider cannot do, for it is not a constructive creature. It shivers in the cold. It makes no garments for itself.