I am not James, but the Animal Archive lists animals associated with various gods on the back cover, and for Desna, it's; Butterflies, moths, caterpillars, owls, sparrows, dragonflies and messenger birds.
Of those, owls fit under the 'Bird' category of a druids animal companion choices. (And work thematically, being flying nocturnal beasties, even if Desna is more of a bug-lady than a bird-lady.) You could flavor it up a bit more, if your GM approves, of having a specific species of Varisian owl that has markings on it's wings reminiscent of the luna moth or a blue-black butterfly (which shouldn't hinder it's ability to function stealthily at night, since it's prey rarely see it coming, and would generally only see it's drab underside anyway...).
A giant butterfly or luna moth might be thematic and cool looking as heck, but you'd have to stretch it off-theme a bit to make it a viable companion, since butterflies aren't renowned for their combat abilities. (You could use giant wasp stats, from Ultimate Magic 37 as a base, and maybe even flavor it as a giant venomous biting butterfly to match the giant wasp stats to your 'giant butterfly companion,' since a dog or wolf sized butterfly is already playing it fast and loose.)
That's a great start. I'll see what I can come up with from there. I like the owl idea with the markings. Thanks again!
They do... but we haven't really published those animals in print yet. Many of the deities come from my homebrew world originally, and I have more detailed accounts of their "sacred animals" in those documents. Those documents, alas, are squirreled away at home.
So working kind of by memory, and kind of by hunch... here's a list of the sacred animals of the core 20 deities of the Inner Sea Region:
Hey, I know it's been awhile since you've posted this, but I'm fairly new to Pathfinder. Since you've put this online, I'm curious as to what you would think a suitable animal companion would be for a druid of Desna (or the Black Butterfly) would be, specifically in game terms. Or at the the very least, a reasonable alternative. I like the butterfly idea, but how in the world would that be expressed specifically as an animal companion? Attacks? AC? Stats? Just curious. Thanks!