How to identify your butterfly – size

6 April 2013

When people tell me they’ve just seen a Common Blue, or a Small Copper, the one thing they always say in a surprised tone of voice is “it was really small” – which is true for these species and others. I think this is one of the things that is not immediately obvious in many of the butterfly identification guides: they usually state the size of the butterfly by giving its wingspan, but that doesn’t have the instant impact of seeing, say, a Common Blue next to a Red Admiral.

This shows a Red Admiral with a Common Blue superimposed on it to show their relative sizes.

This shows a Red Admiral with a Common Blue superimposed on it to show their relative sizes.

Swallowtail with Small Blue superimposed

Swallowtail with Small Blue superimposed

Our smallest butterfly in the UK is the Small Blue, whose wingspan may be as little as 20mm, which is about the size a 1p piece is across – think about it! The largest is the Swallowtail at 85mm – which is nearly 5 x 1p pieces side by side. You are, however, unlikely to see either of these butterflies unless you know where to go looking for them. Species you are more likely to see vary from the Common Blue, Holly Blue and Small Copper (all around 35mm) to the Red Admiral at 70mm. If you see a blue butterfly in your garden it is almost certainly the Common or Holly Blue – the others need rather specialist habitats.

You do not generally get very different sizes of the same butterfly: a Silver-studded Blue is always small and a Red Admiral is always large – though there will always be exceptions, as this is the natural world, not something machine-produced. An adult butterfly – the one with wings – stays the same size from when it emerges from its chrysalis to when it dies. All the growing is done in the caterpillar stage, when the insect needs the sort of nutritious food that helps you grow, which is to be found in leaves, stems etc. The adult drinks nectar for energy to fly and mate, but does not need food for growing – imagine that, a lifetime of eating nothing but the equivalent of chocolate! Unfortunately, it’s also a very short life in this stage.

One of the books which does help you understand the relative sizes of adult butterflies is “Philip’s guide to the butterflies of Britain and Northern Ireland”, published in 2007. The photos on the main pages are sized to fit the space, but at the beginning there are drawings of all the members of the various butterfly families shown at their relative sizes. The other publication which does this is the FSC fold-out laminated guide. Both of these publications are sold by the Dorset Branch of Butterfly Conservation on its sales stall – go to the website to find out where the stall is to be: it appears at many events throughout the County.


One Trackback to “How to identify your butterfly – size”

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )


Connecting to %s

%d bloggers like this: