A very rare butterfly on a rare flower

It has taken me several years to find one of these to photograph; eventually, my GF found one last week in the Buurserzand near Buurse, The Netherlands and took me to it.

This butterfly is related to the common blue, the holly blue, and the silver-studded blue, but needs an even more specific habitat, which is probably why it is rare.

It only lays eggs on gentians (which are rare here), and the survival of the larvae depends on the presence of specific species of ants (also uncommon here) that take care of it; the butterfly larvae emit chemicals that closely match those of ant larvae, causing the ants to carry the larvae into their nests and place them in their brood chambers.

Anyway, it is called Alcon blue (Phengaris alcon), gentiaanblauwtje in Dutch. Here it is inspecting a gentian:

^{Olympus Stylus 1s, 300mm, ISO125, f5.6, 1/500s}