Of the butterflies who make long journeys to find new habitats and wander into Estonia along the way, Scarce Tortoiseshell (Nymphalis xanthomelas), member of the brush-footed butterfly family (Nymphalidae) is a remarkable species who definitely deserves attention.
The Scarce Tortoiseshell in Estonia is similar to the Small Tortoiseshell (Aglais urticae) common in Estonia but it is much larger than the latter and flies in a more dynamic manner. It is easier to mistake it with a species very rare in Estonia—Large Tortoiseshell (Nymphalis polychloros). A good photograph or the butterfly itself is needed to view the insect more closely and differentiate between the two.
The Scarce Tortoiseshell is a species rare in Estonia and it usually wanders here accidentally from the east. However, when conditions are favourable it may stay for a few years, i.e., it is able to survive the winter here. 1925–1928 and 1982–1987 were such favourable years.
In 2012 Scarce Tortoiseshell migration was reported in Estonia, while several lepidopterologists and nature lovers said to have seen and photographed the butterflies. The butterflies went through a successful life cycle and the autumn generation who already grew and hatched here was significantly bigger in number. In some places one could encounter 20–30 butterflies at once feeding on fermenting birch sap on an injured birch trunk. Such places offered great opportunities for photographers since the butterflies spent days and even weeks on the injured birch trunk or its close vicinity. The second generation of butterflies prepare themselves for overwintering so that they would be ready to mate once the warm weather arrives in spring.
Snow-heavy winter offered excellent overwintering conditions for butterflies and the beginning of 2013 brought with it reports of sighting the Scarce Tortoiseshell in early spring, the butterfly having successfully gone through diapause. The larvae feed on willows in large hatches and pupate once the larva stage ends. The pupa stage lasts for about two weeks. In the second half of summer when a new generation has emerged from larvae the Scarce Tortoiseshell is one of the most common brush-footed butterflies in our landscapes.
If the overwintering conditions are good we may hope to meet specimens that have survived the winter who start a new generation after mating during the warm weather in spring. Those, in their turn, shall delight nature lovers and photographers with their attractive appearance, as well as enrich our nature with their beautiful wing patterns and biodiversity.
Allan Selin
