Tuesday, 25 June 2013

Light and shade

Here's an interesting pair from the trap last night: two Peppered Moths, one the standard salt-and-pepper version and the other melanic, or black. The story of the different varieties is famous outside the world of entomology; you can spend hours reading arguments and counter-arguments from creationists and mainstream scientists on the net.

The reasons is the moth's role in the story of change and survive which Charles Darwin (and his less well-known contemporaries especially Alfred Russel Wallace) standardised as the Theory of Evolution. Normally the process of adaption to circumstances is long drawn-out as the less fit are eliminated by predation or disease; but the Peppered Moth's population in the UK has changed in my lifetime, in terms of the balance between the ordinary and melanic types.

In particular, the melanics have declined in remarkably similar proportion to the disappearance of the filthy conditions created by industrial pollution in which their colouring was perfect camouflage. In a famous study, the eminent doctor Sir Cyril Clarke who was also a great enthusiast for butterflies and moths, showed that the decline also paralleled the rise of centenarians in the UK - another indicator of our improving environment. He used the traditional telegrams to 100-year-olds from Buckingham Palace in his data.

It is increasingly unusual to find a melanic version; they were rare in Leeds in my time, even though the pollution had been pretty considerable there into my boyhood in the 1950s.  While we're on the subject of black, here's a pretty red and black Cinnabar to finish up with. It interrupted my efforts yesterday to keep the lawn under control.


Yorkshire Lass said...

I think I had a melanic type in my house last night, it flew in through the bathroom window. I couldn't believe the size of it, never seen a moth that big before.

Martin Wainwright said...

Hi there and sorry for tye delay in picking up your comment. Yes, they are pretty big though if yours was a real whopper it might have been an Old Lady whuch has slightly similar colouring. When a cousin and I were about twelve, we found an Old Lady on rum and treacle which we had smeared on a tree in an uncle's garden in Suffolk. We caused some consternation to my uncle - a vicar - by rushing excitedly into the house shouting "We've caught an Old Lady". Coincidentally, I've just done a bit more on melanic Peppered Moths and their numbers on the blog. All warm wishes, Martin