---

Many thanks, Nikita!
Meanwhile I tried to find more information on this species that is said to be widespread in Central Europe but only rarely observed in Germany. Drees (https://www.natur...scidae.pdf) writes: "The occurrence of this fly is always closely linked to ‘rapids’, which can also be of artificial origin and very small." The larvae live in algae and moss mats and prey on Simuliid larvae. - Well, our Berlin stream is a really slow one, and the fly sat on a bridge railing in a small swamp area. That is not the typical habitat for L. riparia, but in any case there are Simuliids.
Does anyone in our community have experience with the habitat range of L. riparia? I would be very happy to receive some more information!