Saturday, 1 July 2017


It's a while since I've had a dark form of the Peppered Moth in the trap. This one arrived just before our holiday in Scotland, obligingly with a standard version alongside. The contrast is an interesting example of how our minds - or mine anyway - are conditioned to see something slightly sinister in the darker form, especially when it assumes the mien of Darth Vader or one of the other baddies from Star Wars, as in the picture below. 

The Peppered Moth is exceedingly famous because of the role of its different forms in debates about evolution and Darwinism. If you have the time and patience, you can spend many happy hours on the internet learning about this. The brickbats from Creationists make entertaining reading but I think that most rational minds will accept the arguments of mainstream scientists.

Here are the three forms, from the Moth Bible

The key feature of the Peppered Moth is the rise and fall of the various forms in apparent correlation with levels of pollution - the argument being that the respective camouflages suit dark varieties in polluted areas and 'peppered' ones in cleaner surroundings, when they come to roost on tree trunks or walls etc. One of the most interesting pieces of research was done by Sir Cyril Clarke, eminent in both medicine and entomology, who correlated the decline of the dark Peppered Moth in the UK and rise in the number of centenarians (the latter assumed to be due in part to cleaner surroundings).

An obvious issue with this is that evolution is usually discussed in terms of millennia rather than the couple of centuries in which the Peppered Moth population has gone up and down. I guess it remains to be seen how permanent the current superiority of the 'peppered' form will prove to be before we can be sure that genetics are involved, rather than simply bird predation. 

I meanwhile mentioned my visitor on the ever-excellent Upper Thames Moths Blog and asked how many other readers had seen. Characteristically, Dave Wilton and Peter Hall provided detailed answers which I append for your interest below. I have yet to play host to one of the halfway-house forms, insularia, but maybe that time will come.

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