As I understand, life in Arda was brought forth either by Eru Directly, or after the rough draft, Eru gave the go-ahead for that form of life to be legitimatized by giving it the Flame Imperishable.
Now we know Morgoth sought the Flame Imperishable to create life of his own without the old thumbs up from Eru, but only ever managed to twist beings that had already been given the Flame to create beings with actual free will, he was never able to create them from scratch.
But what of Ungoliant? She gave birth to Shelob, who in turn mothered the giant spiders of Mirkwood, but this seems like she created a race, namely the race of spiders. Are all spiders bound to the will of Ungoliant because they do not have the Flame Imperishable, so they are little more than puppets to her? Did spiders receive the Flame Imperishable from Eru? (if so, why?) Are they excluded or some how exempt from this, because they are in fact descendants of Ungoliant, and not a creation of hers?