Identification Help

The root triangle on the backwings have 5 cells instead of 3, which could make it C. boltonii instead of C. bidentata. But according to this document http://www.libellula.org/wp-content/uploads/2016/10/30_1-2_Pix_a.pdf there is about 3% possibility that it is the C. bidentata, when looking on the backwing cells alone. They do variate from 2 to 6 cells where 3 cells is the most common.

But before concluding that its a C. boltonii you have to look at two other characteristics of the C. boltonii, first: that the triangle behind the eyes is yellow instead of black like on the C. bidentata - here it seems to be black.

Second: The C. boltonii also has a weak very fine second set of yellow stripes on the abdomen - which seems to be missing here as well. 

So this must be the C. bidentata.

More information information on the C. boltonii here: https://www.natur-in-nrw.de/HTML/Tiere/Insekten/Libellen/TL-26.html (in German)