Small Tortoiseshell
Aglais urticae


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Aglais urticae

Switzerland, March 2018

Aglais urticae

Suffolk, UK, February 2019

Aglais urticae

Switzerland, February 2018



Switzerland, March 2012

Aglais urticae

Switzerland, February 2014

Aglais urticae

Switzerland, March 2014

Aglais urticae

Switzerland, March 2014

Aglais urticae

Switzerland, January 2016

Aglais urticae

Switzerland, March 2015

Switzerland, June 2006

Switzerland, 3rd February 2007

The underside is camouflaged for hibernation

Switzerland, 6th February 2006

Switzerland, 3rd February 2006

Switzerland, March 2006. The butterfly is on a ski piste (I moved it for its safety!)

Suffolk, 1978

Aglais urticae eggs

Eggs, beneath nettle, Switzerland, April 2011

Aglais urticae caterpillars

Caterpillars, Switzerland, May 2018

Caterpillars, Switzerland, May 2019

Aglais urticae larvae

Older, more dispersed, caterpillars, Switzerland, May 2014

Aglais urticae larvae

Switzerland, May 2014

Aglais urticae caterpillar

Caterpillar pupating


Larva on the point of pupating



Fresh pupa



The same pupa three and a half weeks later, near emergence

Aglais urticae distribution

Distribution

The small tortoiseshell is one of the most familiar butterflies, being common throughout Europe and on the wing from March or earlier until November or even December. I have seen small tortoiseshells in every month of the year (but not in every month of any single year) and in every European country I have visited, I think. However, this should not count against the fact it is also one of the most beautiful - something often overlooked!

In the Alps, the small tortoiseshell is the only butterfly to emerge while there is still plenty of snow around and it even seems to enjoy cruising over the pistes. In the Rhône Valley it typically wakes up towards the end of January or the beginning of February, usually shortly after the first Queen of Spain fritillaries have flown. I regularly visit a favourite site where Queens defend territories alone until the first small tortoiseshells emerge and thereafter tend to get bullied by the more agressive tortoiseshells. Because of this very early start to the year, and because nettles are available pretty much all year round in much of Europe, small tortoiseshells are able to fit in two or sometimes more broods during a single season in most of Europe (there is just one generation in the far north and at altitude). Caterpillars from eggs laid by the hibernating generation feed up during April and May and are usually on the wing in June. These summer butterflies then produce at least one further generation before their offspring enter hibernation again. Small tortoiseshells are deep hibernators. Some individuals will sleep from late July through to March before waking up perfectly fit to fly, feed and breed - unlike red admirals, for example, which need a shorter winter.

Eggs are laid in batches on the undersides of nettle leaves. The caterpillars then feed gregariously until the last instar, when at some stage before pupation they wander off individually.

There are reported steep declines in small tortoiseshell populations in recent years. I have to say, I have not noticed this in Switzerland, and since moving to the UK have seen plenty of this species. Speculative causes include the parasitoid, Sturmia bella, but this has not been proven guilty beyond all reasonable doubt.