Gomphus simillimus (Yellow Clubtail) is a mainly south-western European species with populations from Morocco in the south to southern Belgium in the north. Like most other clubtails, it’s a species of streams and rivers.
Yellow Clubtails look very similar to Pronged Clubtails (Gomphus graslinii). The easiest way to identify the two species is by looking at the diagnostic ante-humeral markings. In Pronged Clubtails, the yellow line between the black ante-humeral markings is smaller than the black parts, in Yellow Clubtails the yellow and black parts are about equally wide.