#2
The catalog by Gagné and Jaschhoff (2014) considers them synonyms:
pteridis. Widespread Europe, Japan. Pteridium aquilina (Polypodiaceae).
Cecidomyia pteridis Müller 1871b: 100. UK: England, vic. S. Norwood; ST; L; lost. This name has been overlooked since its first use but the gall described is the same as that described for
C. filicina.
Cecidomyia filicina Kieffer 1889c: 191. France: Bitche & St Avold; ST; ♂,♀,L,egg; lost?.