Luckily, in Schleswig-Holstein (where the picture was taken) all individuals of A. subarctica belong to f. interlineata (cf. Die Libellen Schleswig-Holsteins, 2015, p. 219). This means that they show a well developed third yellow stripe between the two main ones on their thorax side. Since the individual on the photo has only two stripes (with a small dot between them) it belongs to A. juncea