"Do you like the fly?"
Translation:Dych chi'n hoffi'r pryf?
In English or Welsh? I've never seen it in either but it could be another Welsh dialect to mine.
Well I'd definitely suggest it as an alternative answer then (you never know how many words there are for things in Welsh).
What other word would you use for fly as opposed to insect? Duolingo so far has used pryf for both.
I just use pryf for both. I checked a dictionary and words for "Fly" inlude, "Cleren"(F) and "Pryf"(M), and the words for insect are either "Pryf"(M) and "Pryfyn"(M). So to more specific to a "Fly" you could use "Cleren" and to be more specific about an insect you could use "Pryfyn".
like is a verb here.
So it's not "like the fly" but "Do you like ...?" with the fly being the thing that is liked, the thing that the person you are asking likes or does not like.
It's not an idiom it just means "like the fly" as in the specific insect here.