I found this big Perlodes larvae under a stone in a cold and unpolluted alpine creek.
Perlodes are medium to large stoneflies, this one was 3 cm. including cerci and antemnas
Typical straight external border of the wing case of a perlodes (as opposed to the rounded ones of the Perlidae family)
The absence of branched gills underneath and on the side of the thorax is a key difference distinguishing the Perlodes from the Perlidae genus.