Cecidomyia \Cec`i*do*my"i*a\ (s[e^]s`[i^]*d[-o]*m[imac]"[i^]*[.a]), prop. n. [Nl., fr. Gr. khki`s, khki^dos, a gall nut + myi^a a fly.] (Zool.) A genus of small dipterous files, including several very injurious species, as the {Hessian fly}. See {Hessian fly}. [1913 Webster]