A week ago, we published a picture of a butterfly bathing in springtime sunshine, thinking it to be a Small Tortoiseshell – prophesying a colourful summer. Not quite! «Delving deeper into the picture, with colleagues, we arrived at the conclusion that this isa Yellow-legged Tortoisehell,» announced biologist Mati Martin, lecturer at University of Tartu’s faculty of science and technology.
This is a species quite rare in Estonia, which also closely resembles Blackleg Tortoiseshell, more widely seen westward.» To an ignoramus, Yellow-legged Tortoisehell is ever so similar to our familiar Small Tortoiseshell.
Yellow-legged Tortoisehell is widespread from Central Europe to the Sea of Japan. According to Mati Martin, Yellow-legged Tortoisehell strongly immigrated from the south last year, being seen in large numbers all over Estonia and even in Finland.
«Like Small Tortoiseshell, European Peacockand Common Brimstone, this species also has imagoes that winter; terefore, we can see the rare species around, so early in spring,» explained the biologist. «Now, it will be quite interesting to watch if this species will linger on our territory for a longer time – or will the change of life prove too tough for it here. Their caterpillars feed on willows, which are abundant enough around here, though.»
It is not quite clear why a species of insects will, once in a while, multiply and start migrating.
«Probably, they have some sort of a genetic trigger, which, from time to time enhances massive breeding and, thus, also potential migrations from main distribution area,» noted Mati Martin. «The goal of migration may be possessing new habitats.»