Who is Beelzebub in "The Battle of the Books"?

In the Bible, Beelzebub, otherwise known as the Lord of the Flies, is a Philistine deity. As a false god, in the Christian tradition he's often synonymous with the Devil. In the context of Swift's The Battle of the Books, it's in his capacity as Lord of the Flies that Beelzebub makes an appearance.
While the ancients and the moderns are busy battling for supremacy in the library below, a little drama is taking place up at the corner of a large window. There, a bee has blundered into a spider's web, ruining all the spider's painstaking handiwork. When the bee first crashes into the web, the spider is frightened, immediately fearing that Beelzebub has come to take revenge for all the flies he's killed and eaten.
That's the literal meaning, of course. But as this is a satire, there's another more allegorical level of meaning involved. The spider represents the modern author, who's only capable of creating out of himself and his own resources, just like a spider spinning a web out of its own abdomen. The bee represents the superior ancients—those venerable poets, playwrights, and philosophers who gathered their inspiration from nature, just as bees gather pollen from flowers.