* A cluster of spiders
* A colony of spiders
* A tangle of spiders
* A web of spiders
You can also get creative and use other nouns depending on the context, such as:
* A horde of spiders (for a large, menacing group)
* A parliament of spiders (for a group that seems to be deliberating)
* A swarm of spiders (for a group that moves quickly and in a coordinated way)
Ultimately, the best collective noun for a group of spiders is the one that best fits the situation and your creative vision.