The pretty Baton Blue is among the more endangered butterflies in Finland. To the untrained eye all blue wing butterflies are the same and it requires an expert to identify the species. However, the Baton Blue is easy to identify based on behaviour and habitat alone: it requires warmth, semi-open slopes and prefers sandy or gravel land. The species spread to Finland after the breckland thyme it favours reached Finland just after the ice-age. However, the regular forest fires that once kept the woodland sparser and open are now seldom seen, resulting in the species becoming critically endangered.
It flies at different times of the summer and according to the weather conditions. Generally, they fly for a month if they survive that long. Male blue batons are the first to spread their wings, appearing on an average a week earlier than the females. Males are easy to observe during as they will put on a display over breckland thyme but only within a few square metres as they defend their territory from other blue batons. However, the female will travel on longer journeys in search of suitable breckland thyme on which to lay her eggs, which are laid one at a time with a slight change in place between each egg. The caterpillar is dependent on breckland thyme, preferring the blooms, but also eating the leaves.
The blue baton experiences great changes in its population from year to year – as is common for most butterfly species in Finland. Furthermore, its spread is limited by the amount of breckland thyme on the already niche habitat it prefers. The greatest threat to the species is the reduction of habitat due to forest growth. Its only known area in Finland is the Säkylänharju shooting range for the Finnish army, something wwhich actually helps maintain the blue baton’s desired habitat while simultaneously threatening individual butterfies.
Photo: Erkki Kallio