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Could somebody reveal an animagus by incanting the Homenum Revelio spell?

Let's say somebody shouted Homenum Revelio in the presence of a nine-toed rat named Scabbers. Would that person suddenly know that Scabbers is actually a human in disguise?

Or expose a tabloid writer hiding as a beetle?

This question about Homenum Revelio does not have an answer. Nor do other sites I checked.

I prefer answers based on statements or writings by J K Rowling rather than speculative answers.

RichS
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No. It can only be used on humans.

Homenum Revelio is a spell that detects the presence of human beings (not animals).

"But before we go any further, I think we'd better check", whispered Hermione, and she raised her wand and said "Homenum revelio".
Nothing happened.
"Well, you've just had a big shock," said Ron kindly. "What was that supposed to do?"
"It did what I meant it to do!" said Hermione rather crossly. "That was a spell to reveal human presence, and there's nobody here except us!"
(Deathly Hallows, Chapter 9, A Place to Hide).

So it detects humans, not animals. This is confirmed by J.K. Rowling in the linked-to question.

Dumbledore, who could perform magic without needing to say the incantation aloud was using 'Homenum revelio' - the human-presence-revealing spell Hermione makes use of in Deathly Hallows.
(Bloomsbury Live Chat).

Now Animagi are clearly humans on one level. A person who transforms into their Animagi form retains their memories, intellect, agency and identity. But the important thing about Animagi is that the person becomes an animal. It's a holistic transformation, not a disguise.

He hardly heard what Professor McGonagall was telling them about Animagi (wizards who could transform at will into animals...
(Prisoner of Azkaban, Chapter 6, Talons and Tealeaves).

Once transformed, the Animagi is an animal, not a human. So the Homenum Revelio spell would have no effect on them, and certainly wouldn't force them to transform back into their human form.

There is a spell that can do this. It's the one that Lupin and Black use on Pettigrew to force him to transform in Prisoner of Azkaban. However, this spell is never named (as Lupin and Black never make an incantation of any kind) so we can't definitively say what it is. I think that we can rule out Homenum Revelio, though. It doesn't affect animals and it isn't used for transformation (just for identification).

RichS
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The Dark Lord
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  • Nice try, but my question is not about whether the spell would reveal the presence of (non-human) animals, but about whether it would reveal whether an animal was a human transformed. – RichS Jul 04 '17 at 18:05
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    @RichS But the clarification is important since the spell only works on humans. Revealing the presence of humans is all that it does. Since Animagi are not humans but animals when transformed it would not detect them. The person is not a human at the time so Homenum Revelio wouldn't detect them. – The Dark Lord Jul 04 '17 at 18:44
  • I am not asking about detecting the presence of animals. If the rat was in your hand, you would not need to detect it because you know the rat is there. I am asking about whether you could use the spell to determine if the rat is transformed human. – RichS Jul 05 '17 at 02:16
  • @RichS As I say, the only spell which we see that does that is the one that Lupin and Black use, and that can't have been Homenum Revelio Develop as it also forced Pettigrew to transform (which is not part of the HR remit). I think I misunderstood 'reveal' to mean 'transform' in your original question, which is why I came at it from this angle. I think my answer is as close as you're going to get, though. JKR hasn't commented on this specific point as far as I'm aware. – The Dark Lord Jul 05 '17 at 07:23