Setacera is o.k. This large anal proleg is used for hold on to plants and filamentous algae. Ephydra spec. has about the same habitus but has a dorsal pattern of flattened spines (see http://www.dipter...to_id=8304 and http://www.dipter...to_id=8322) and occurs in brackish/marine waters.
Setacera larvae and pupae cannot be Identified to species level for not all species have been described. In the Netherlands we have 3 species. It may be usefull to breed the larvae or pupa to the adult stage and identify the adult. breeding pupa of Ephydridae is very easy: put the pupa in a glass vial with some plant material and cover it with cottonwool. After a few days or 1-1.5 week the adult will emerge.
I thank you a lot Atylotus
and propose the clip video made during the observation of two specimens of this larvae
We can see very closely the hooks, the skin and the mouth apparatus
