Why doesn't this exist? :)

No idea. Four stars for you. It can still be five stars with a name change, though. I saw the name and expected a green version of Skittering Skirge or Skittering Horror...

Thank you! I nearly called it "Spider" but decided it was better not to. Any suggestions? I didn't want to call it "small spider" as it's still significantly bigger than a natural spider, just not giant-giant.

Giant Spiderling? Spiderling is evidently the name of a baby spider. I couldn't get much more from a glance at Wikipedia. It's just far too much information to pile through to figure out "which spiders are small". Colloquially, though, most of the internet likes to agree that small spiders are often called "Garden Spiders"... whatever that's supposed to refer to.

Hm. Maybe something like garden spider but bigger -- forest spider? brush spider?

Or maybe this should make a token, to fit with spider spawning?

Excellent call. I think it's better as a creature than as a token, though if it was in the same block as Spider Spawning or Gloomwidow's Feast then yeah, it might as well be a sorcery to use the same token.