Identification Help
The root triangle on the backwings only have 3 cells instead of 5, which in theory could make it C. bidentata instead of C. boltonii.
A more secure way to identify it is looking at the triangle behind the eyes. If the color is black it is C. bidentata.
More information here: http://www.natur-in-nrw.de/HTML/Tiere/Insekten/Libellen/TL-25.html (in German)