"A bee and a butterfly are flying."
Translation:Pszczoła i motyl lecą.
Well, I think we rather don't accept diminutives unless it's stated that's a "little butterfly".
Pszczoła i motyl fruwają should be accepted as correct. Fruwają is formed from the verb fruwać and means the same as to fly.
Sure, added now.
Wait, it's not that 'sure', although yes, it works here. The equivalent of "lecą" (right now) is "fruną" (from "frunąć"). However, as there is no destination/direction mentioned, it's a perfectly fine interpretation to decide that they are just 'flying around'. And thus, "latają" and "fruwają" work as well. But if it was "A bee and a butterfly are flying to this tree", it could only be "lecą/fruną do tego drzewa".