The peppered moth

Being a wildlife photographer I probably pay more attention to camouflage than most. I often need to utilise camouflage to remain hidden from my ‘prey’ but my ability to hide from view pales into insignificance when compared to some of the strategies employed by the wild creatures that I often try to photograph.

Camouflage is normally used by creatures to avoid being seen and eaten. As a result, we can find many stunning examples of camouflage in creatures towards the bottom of the food chain. 

One of the stories of camouflage that I can still remember from biology lessons at school relates to the peppered moth, Biston betularia.

A camouflage question

The peppered moth has a cryptic pattern which helps it to blend in with the lichens on the trees where it hides. This camouflage is remarkably good when the lichens thrive but what happens if the lichens die out?

The lesson we learnt at school related to the industrial revolution when many lichens in central England were killed by pollution in the air and the bark of trees was either bare or worse still covered in soot. 

A typical light-coloured peppered moth started to stand out like a sore thumb. We were taught that over a period of time peppered moths began to change colour, becoming darker. This process was thought to be achieved through evolution and natural selection. 

It is clear that darker moths would survive better and pass on their genes to the next generation, but if evolution was taking place then light moths would all gradually be getting darker and this was not the case. 

 Scientists now realise that there are two distinct colour forms of peppered moth and it is just the frequency of these two colour forms which vary according to local conditions.

In Manchester the first dark forms of the peppered moth were noted in the middle of the 19th century but by the end of that century they accounted for 98% of the total peppered moth population. 

Since then they have declined and current estimates suggest that the dark form will account for just 1% of the population by the end of this decade.

Peppered moths can be seen throughout the summer in gardens across the UK.

Find out more about British moths

Peppered moth key facts

Wingspan: 55mm
Distribution: Asia, Europe and North America
Breeding habits: breeds once a year in the UK
Food source: peppered moth caterpillars eat bramble, rose, hawthorn, elm, willow and other plants
Overwintering: pupae overwinter in the soil