Whom/Who with people and what with insects, animals?

<p>I have seen that animals and insects are regarded as which, it, etc? Can anyone explain to me why this is so?</p>

<p>In grammar the noun forms are person, place, or thing. And an animal is not a person, nor a place so it has to be a thing. Good question.</p>

<p>So what are animals supposed to be referred to as? It? They?</p>