The spiders knew they were being scanned by human eyes.

He was afraid the spiders might know of their presence.

How could these young spiders know anything of the ancient history of their race?

The spiders have always known that human beings are their most dangerous enemies.

I believe it's because the spiders have always known about will-power.

The spider doesn't know the horses by name, of course, but that fits the pattern.

A spider would have known long ago that he was wide awake.

He didn't know when it began, but the spiders knew of the change about third dawn.

It was doubtless confused, but spiders simply do not know terror.

But of course the spider didn't know, having had no experience with humanity prior to this adventure.