The damselflies in the photos are called banded demoiselles (Calopteryx splendens), weidebeekjuffers in Dutch.
I saw a few for the first time this year near the river Dinkel in The Netherlands two days ago. This species likes running water like streams; you won't find them near pools.
As far as I know, these are the only dark blue damselflies in The Netherlands, and they have a metallic paint job to boot. This is the male of the species:
Olympus Stylus 1s, 300mm, ISO200, f8, 1/200s
They are a pain to photograph, as they prefer to sit over the water on vegetation, and they like the full sun.
So, unless you have a very long lens, you will be standing in the mud enduring over 30oC trying to get a shot with a low-enough contrast so the camera sensor can handle it. Get too close and they will fly off; a very skittish species, this.
Olympus Stylus 1s, 300mm, ISO200, f8, 1/125s
This is the female of the species. The females are green and don't sit out in the open as much as the males:
Olympus Stylus 1s, 300mm, ISO200, f5.6, 1/500s
The metallic green is almost too bright for camouflage:
Olympus Stylus 1s, 300mm, ISO200, f5.6, 1/250s
On the rare occasions they spread their wings, you can see these too are green all over:
Olympus Stylus 1s, 300mm, ISO200, f5.6, 1/250s
Pretty little beasts, aren't they? Thanks for watching!