The music of aria "Fidi amanti che costanti", in third act of Vivaldi's opera "Dorilla in Tempe", is not extant. A version of it, however, was performed in the recent Naïve recording, but with no clue about its provenance. Only on the very last page of the booklet one can find the following mention:
Special thanks to Frédéric Delaméa for the reconstruction of the aria "Fidi amanti"
I'm quite certain that Delaméa took the music from some aria of another Vivaldi opera to fit the new text, but I couldn't find which one. Does anybody know more? You can listen to this aria here:
In his old recording (1994) Gilbert Bezzina also reconstructed that aria, using the music from "Or di Roma forti eroi" in Vivaldi's opera Farnace, but the result was not very satisfying and the new reconstruction by Delaméa is different.