Unexpected creature sizes

[Fiery Diamond]

So I was looking at the Pathfinder 1E list of basic familiars, and I discovered something odd. It started with the thrush, which in real life is such a broad term that it includes a range of sizes of bird. It's listed as diminutive size. Okay, I figured, even though a bluebird is a thrush and would clearly be fine size (6 inches or less), maybe they just had a larger type of thrush in mind. Then I looked further. The cockroach. I don't know about you, but I'd be freaking terrified if I encountered a cockroach longer than six inches, and yet that's listed as diminutive as well! Then I looked at the butterfly, which is also listed as diminutive. Now, the butterfly stats are also used for moths, and if we go by wingspan, rather than length, an atlas moth could fit in that size category... except that if you read descriptions of sizes of birds and bird monsters, it's clear that the size categorization explicitly goes by height or length of the bird and NOT by the (often significantly larger) wingspan.

What gives? Why are some of these creatures listed in what is obviously a larger size category than they should be, realistically? Why even have the fine size category if you're going to decide to use the diminutive size category for creatures that should be fine? Does anyone have any clue what's going on here?

[Crake]

Content churn leading to devs making only short passes on their work is most likely whats going on

[Biggus]

It's the same in 3.5, I've often been puzzled by it. Oddly the size categories for larger creatures are generally right as far as I can tell, but tiny or smaller creatures are often clearly wrong. Weasels are fine or diminutive but are listed as tiny for example.

[Maat Mons]

Maybe the writer said to himself, "Well, the entry for Mosquito Swarm says those are diminutive, and a butterfly definitely isn't smaller than a mosquito…"

[Biggus]

Thinking about it, I wonder if it's because these creatures are often used as familiars and a +16 bonus to Hide for being Fine would make them effectively invisible at lowish levels.

Edit: and give them +8 attack and AC, as opposed to +4 for diminutive.

[ShurikVch]

In the 3.5, Butterfly and Hummingbird are Diminutive; Mouse and Sparrow are Fine...

[Fiery Diamond]

In the 3.5, Butterfly and Hummingbird are Diminutive; Mouse and Sparrow are Fine...

...Okay, I'm starting to believe the "didn't actually look at their work after writing it before publishing it" idea. Because there's just no excuse for that kind of inconsistency.

[Rebel7284]

Maybe in some of those cases they envisioned the biggest sub-species possible in order to make them more likely to be a threat in combat? Doesn't explain all the inconsistencies, but hey, battle weasels!

[ShurikVch]

Weasels are fine or diminutive but are listed as tiny for example.
Steppe polecat (https://en.wikipedia.org/wiki/Steppe_polecat) is not just solidly in the Tiny range - but, actually, pushing it closer to the Small...

[Beni-Kujaku]

It's really a problem with the Fine category giving so many bonuses that devs actively avoid putting creatures in that range. It's almost more a theoretical size category rather than a real one. Actually, there is not a single creature in the original monster manual that is Fine, despite this size category being listed in all tables. Toads, centipedes, bats and locusts should of course all be Fine, but they're not, probably because the size category was added too late in development. No Fine creature in MM2 either, and the only non-swarm non-symbiont Fine creatures I could find in the entire 1st party are the Hoard Scarab (meant as a swarm), the Puppeteer (meant as a pseudo-symbiont), the Hairy Spider, and the online Speck and Minim Ecto Fragments (https://web.archive.org/web/20161031215555/http:/archive.wizards.com/default.asp?x=dnd/psb/20030725b) and Ember Spawn (https://web.archive.org/web/20070729191916/http:/wizo.wizards.com/ka/KnowledgeArcana06.pdf) (download link). Actually, the whole size category was removed in the next editions.

The previously mentioned mouse and sparrow are respectively from Dragon Magazine and only mentioned as a form for the hengeyokai in Oriental Adventures, which probably circumvented the instinctual "Wait, what are we doing?" response the devs would have gotten writing an actual statblock (though considering how much cheese sparrow hengeyokai have created, they probably should have just made it Diminutive as well).


Other surprising size categories:
Gricks and Rust Monsters are Medium, while I always envision them as Small (and the movie didn't help that). A spider eater looks like it would be Small or Tiny, but is actually Large.

[Biggus]

Steppe polecat (https://en.wikipedia.org/wiki/Steppe_polecat) is not just solidly in the Tiny range - but, actually, pushing it closer to the Small...

Yes, there are members of the weasel family which are bigger, but they're generally known as stoats, polecats or mink rather than weasels.

[ShurikVch]

No Fine creature in MM2 either, and the only non-swarm non-symbiont Fine creatures I could find in the entire 1st party are the Hoard Scarab (meant as a swarm), the Puppeteer (meant as a pseudo-symbiont), the Hairy Spider, and the online Speck and Minim Ecto Fragments (https://web.archive.org/web/20161031215555/http:/archive.wizards.com/default.asp?x=dnd/psb/20030725b) and Ember Spawn (https://web.archive.org/web/20070729191916/http:/wizo.wizards.com/ka/KnowledgeArcana06.pdf) (download link). Actually, the whole size category was removed in the next editions.

The previously mentioned mouse and sparrow are respectively from Dragon Magazine
Actually, there are also Mouse Familiar (Dungeon Master's Guide) and Shrew Familiar (Tome and Blood)



Yes, there are members of the weasel family which are bigger, but they're generally known as stoats, polecats or mink rather than weasels.
AFAIK, there are no "stoat" in the D&D, the only "polecat" is the Giant Polecat (and it's - only in the 4E), and Mink in 3.5 is Diminutive

On the other hand - many of IRL weasels (Back-striped (https://en.wikipedia.org/wiki/Back-striped_weasel), Indonesian mountain (https://en.wikipedia.org/wiki/Indonesian_mountain_weasel), Japanese (https://en.wikipedia.org/wiki/Japanese_weasel), Malayan (https://en.wikipedia.org/wiki/Malayan_weasel), Siberian (https://en.wikipedia.org/wiki/Siberian_weasel) weasels) are all more-or-less in the Tiny range

[Remuko]

Rust Monsters are Medium, while I always envision them as Small (and the movie didn't help that).

i just assumed those were baby rust monsters in the movie tbh.