The ultrastructure of the spermatozoon of the following gall‐midge flies (Diptera, Cecidomyiidae) is described:Rhopalomyia foliar‐um, Wachtliella riparia, Oligotrophus juniperinus, Semudobia betulae, Cys‐tiphora sonchii, Jaapiella cirsiicola, Rabdophaga rosaria, Macrolabis luceti, Dasineura pseudococcus, D. loewiana, D. affinis, D. serotina, D. euphor‐biae, D. gleditchiae, Mikiola fagi, Lasioptera rubi.The spermatozoon of the whole Oligotrophidi group is characterized by the presence of a great number of singlet microtubules in addition to an axoneme of 9+0 type. The microtubules penetrate peripheral outfoldings of the cell membrane. The spermatozoa are immotile and the microtubu‐lar doublets lack dynein arms. The nucleus contains large dense bodies and there is no acrosome. Sperm characters in the super‐tribes Oligotrophidi and Lasiopteridi are very similar; there are thus no strong reasons to separate these groups. Sperm data rather support the proposal that subfamily Cecidomyiinae is subdivided in three supertribes only (Lasiopteridi. Asphondyliidi and Cecidomyii‐di).