Hanukkah Solo wrote:
I don't remember any mention of spiders or wargs, but we do know the White Council did attack Dol Guldur to drive the Necromancer/Sauron out. It wouldn't surprise me if PJ added the spiders and wargs in to spice things up a bit.
The spiders would have been around Mirkwood generally and perhaps more populous in the southern portion near Dol Guldur after the Necromancer set up shop. Might as well have them involved, right?