#5
It is a Stratiomyidae from the genus Stratiomys. The terminal segment is small and elongated which is typical for Stratiomys. If you look closer you'll see/find a circular row of floating hairs at the tip, which all aquatic species of Stratiomyidae have. The length/width ratio of this segment as well as the size of the tubercles at the lateral side of the fourth and fifth segment are diagnostic. The habitus (and habitat) reminds me of S. longicornis. The terminal segment is too short for S. singularior. This mature larva is probably on his way to emerge. As you may now, Stratiomyiidae doesn't have a a true pupal stage as in all other Dipterans. The larval skin is also the pupal skin and the adult emerges from this pupal skin on land.