They even go so far as to dig their fangs into the bait, following the rule of the preliminary poisoning.

Then and then only the mistake is recognized and the tricked Spider retires and does not come back, unless it be long afterwards, when she flings the lumbersome object out of the web.
There are also clever ones.

Like the others, these hasten to the red-woollen lure, which my straw insidiously keeps moving; they come from their tent among the leaves as readily as from the centre of the web; they explore it with their palpi and their legs; but, soon perceiving that the thing is valueless, they are careful not to spend their silk on useless bonds.

My quivering bait does not deceive them.
It is flung out after a brief inspection.
Still, the clever ones, like the silly ones, run even from a distance, from their leafy ambush.

How do they know?
Certainly not by sight.
Before recognizing their mistake, they have to hold the object between their legs and even to nibble at it a little.