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Can I say,

The butterfly rested on / at / in the flower.

The butterfly is on / at / in the flower.

The butterfly is sucking the flower.

The butterfly is staying on the flower.
Comments  
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The butterfly rested on the flower.

The butterfly is on the flower.

The butterfly is sipping the flower's nectar.

The butterfly is resting on the flower.
Thanks. Can I say,

The butterfly is standing on the flower.

P/s: "butterfly", we use "is sipping"
"bee", we use "is sucking"?
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You continue to look for rules. I like sipping better for butterflies because it is daintier.

Butterflies have developed a long proboscis that can probe the flower for nectar. It is like a flexible straw that is kept coiled next to the body in flight but is extended to sip the sweet fluid when the butterfly finds a suitable flower head.

In different contexts you could use sip, suck, probe, nectar (v), retrieve, etc.
That means it is also correct if I say "The butterfly is sucking the nectar." Right? Just depends on the text.
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Yes.
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How about this?

The butterfly is standing on the flower.
Vincent TeoHow about this?

The butterfly is standing on the flower.

Yes that's fine, although we don't really think of butterflies standing. I would be more likely to say "the butterfly is lying on the flower", or even better would be just "the butterfly is on the flower". It's location on the flower is implied as the petals, because it can't really be anywhere else.
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Butterflies do not 'lie' where I come from, unless they are dead; it may be otherwise in Cornwall. Again, Vincent, there are many choices-- your job inacquiring English is to learn the natural ones. If we are speaking of a butterfly immobile upon a flower head, then I myself would perhaps choose 'The butterfly is perched on the flower'.
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