As July comes to an end, we’d like to introduce a truly beautiful butterfly that can still be seen in nature until early August – the alcon blue (Phengaris alcon).

The male Alcon Blue has bright blue upper wings with darker margins and lacks the black spots characteristic of other species in the same genus. The female, on the other hand, is dark brown with a bluish base on the wings and faint, darker markings.

The Alcon Blue is a specialist species that depends on a specific host plant - Gentiana pneumonanthe. In Europe, it has also been observed using the Cross-leaved Gentian (G. cruciata). The female lays easily noticeable white, spherical eggs on the buds, flowers, or stems of the host plant. After hatching, the caterpillar feeds inside the flower of the gentian for about three weeks.

You can read more about the Alcon Blue and how you can help protect this species in its fact sheet (PDF version available here). Fact sheet design: Madara Eihe, Kristīna Bondare.

The Alcon Blue is threatened by the abandonment and transformation of low-productivity grasslands – including fertilization, intensive grazing, early mowing, drainage, afforestation, and eutrophication – all of which lead to the loss of its host plant.

In Latvia, it is classified as Endangered (EN) due to its very small population and the rarity of its host plant. In Europe, it is considered Near Threatened (NT), but is endangered in many countries.