gadfly (noun) – a fly that lives on animals, or: an irritating person who asks questions all the time or who criticizes constantly
Here are some examples of how you can use gadfly:
The horse was flying his tail, trying to beat off the gadflies that bit his skin.
The Prime Minister opened the newspaper and after reading a few minutes said: “When will that gadfly finally tire of making fun of me?”
I wanted to taste some of the mouth-watering cakes, but there was that gadfly voice again in my head that told me: “And what about your bikini diet?”
The movie star had finally found the perfect hiding place where he could be free from those gadflies, the paparazzi.