How to identify: the Small Tortoiseshell

Scientific name: Aglais urticae

Why are we looking for it?

This beautiful butterfly used to be found in large numbers throughout the UK, but it has suffered a rapid decline in recent years, especially in southern England. Research into the cause of this decline is ongoing, but a recently introduced parasitic fly called Sturmia bella is likely to be one factor.

Help us find out more about this once common garden species – where is it now and is it doing better in urban or rural areas?

 

Small Tortoiseshell

Identification features

  • 45-60mm wingspan
  • brightly coloured orange and black wings
  • row of blue spots around the wing edge
  • undersides of the wings are dull brown, for camouflage

Identification tips

Could be confused with…
Other orange-coloured butterflies such as the Comma (Polygonia c-album) or Painted Lady (Vanessa cardui), but the Small Tortoiseshell is the only one with blue dots around the wing edges.

Where can I find it?
Across the UK, in both urban and rural areas. Look out for ‘nests’ of Small Tortoiseshell caterpillars on nettles. Adults regularly visit flowers, or can be seen basking in sunny places.

When can I find it?
Small Tortoiseshells are one of the earliest flying butterflies in the UK. Adults can be seen from early spring through to late autumn. The adults hibernate during the winter - you may be lucky enough to spot them in outbuildings like sheds and garages.

Lifestyle

Small Tortoiseshell larvae (caterpillars) eat the leaves of nettles. Adults feed on nectar from a wide variety of flowers, using their long tongue (called a proboscis) like a drinking straw to suck up nectar.

Adults hibernate during the winter in tree crevices or outbuildings like garages and sheds. They emerge during early spring and mate.

Females lay clumps of bright green eggs on the undersides of nettle leaves. Hairy, black and yellow caterpillars hatch after 1-3 weeks. The caterpillars live in groups and build webs for protection. They grow rapidly on their diet of nettles before entering a pupal stage after around one month of continuous eating. After about a month as a pupa, adult butterflies emerge and begin mating again to restart the cycle. There are usually two cycles (or generations) per year.

What does it do for us?

This is a beautiful and harmless insect, which pollinates plants and provides food for birds and other wildlife.

Interesting fact

When threatened by a predator, Small Tortoiseshell caterpillars swing their bodies from side to side in unison.

 

Think you've seen one?

Small TortoiseshellTake a photo and complete our simple online form to help us learn more about their distribution.

Submit a sighting

Where have they been seen?

UK mapExplore our interactive map and see where the Small Tortoiseshell has been recorded so far.

Species Quest results map

 

Need help with identification?

Simply upload a picture of your find to iSpot or the Natural History Museum's Bug forum and an online community of experts and enthusiasts will do their best to identify it.

Visit the iSpot website

Visit the Bug forum on the Natural History Museum's website

 

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