The Small Tortoiseshell (Aglais urticae) is a butterfly that most people recognize. When not by name then by its looks. The reason is simple: It is one of the widest spread and most common butterflies across Europe.
Regardless of being a common species there is an interesting fact that can be observed in Finland. In some years, it’s the most common species and appears everywhere. Then suddenly, there might be a year when people hardly make any sightings at all.
Overwintering as adult the Small Tortoiseshell is a really early butterfly to wake up in spring. They also breed early and develop fast which allows them to fly in up to three generations even as north as in Finland.
2014 has been been a poor year for this species. Even the lepidopterists can only speculate what has caused the Small Tortoiseshell to almost disappear after a cold period early summer. I sighted many individuals of this species early spring. Next, I spotted a normal amount of caterpillar “nests”. But suddenly, it was quiet. By the time the butterflies should have hatched I only saw three individuals in late summer.
That the butterfly had a hard time this year can also be seen in my captures. All expect one are from spring. I waited for the fresh and colorful specimens to fly in high summer. But they never came.
The Small Tortoiseshell is probably the best butterfly species for learning how to rear caterpillars. They’re relatively easy to take care of, are not too demanding and their food plant, nettles, are easily available. They develop fast which makes it more convenient if you want to show this spectacle to your kids (who may not have the patience to wait for a chrysalis to overwinter). Keep an eye on nettles nearby. They form a web around their nest at the very early stage which makes it simple to track them down.
Though I didn’t raise any caterpillars of this species in 2014 I didn’t hesitate to get a close look with my camera whenever I found caterpillars. Here’s some shots showing the development from small caterpillars to chrysalis.