Peppered Moth

Teachers in schools often use the evolution of the peppered moth as a good example of Darwin’s theory of natural selection.

The Peppered Moth is a small insect of merely a few inches that has tiny black spots on its wings. Hence, the name Peppered Moth. It exists as the best example of evolution in the history of science. Researchers discovered a special gene whose presence in this moth turned its whole color black. This allowed them to study natural selection and helped in understanding evolution. 

Peppered Moth Species, Types, and Scientific name

The peppered moth Biston betularia is a species of European moth in the family Geometridae and of the order, Lepidoptera. There are only one known species Biston betularia of the Peppered Moth, however, there are a few subspecies.

The Peppered Moth may be found in three different colors, pale grey, dark black color, and black with white spots coloration. This ultimately helped in learning about natural selection. But an unfortunate thing about their species is that they became very sparse in number during the 1980s but soon after, they began to repopulate.

While there are a lot of moths in the world, more than 160,000, the exact number of the Peppered Moth population is not known yet. They are, however, found in various parts of Europe.  

The seven subspecies of the Peppered Moth, as described by scientists, are as follows;

1. Biston betularia alexandrina 
2. Biston betularia cognataria
3. Biston betularia contrasta
4. Biston betularia fumosaria
5. Biston betularia nepalensis
6. Biston betularia parva
7. Biston betularia vlachi

Appearance: How To Identify Peppered Moth?

The Peppered Moth is best identified because of the markings on its body. This helps them camouflage with their surroundings and protects them from unwanted dangers. Their habitat usually consists of tree bark which makes their camouflage perfect for protection.

It has a broad, long, and slender body that resembles a twig-like caterpillar. It is covered in fur and has long wings as narrow and straight that it prefers keeping on the outside. The wings also have brown bands on the frame and carry a wingspan of 1.5 – 2.5 inches. The color is usually white with black pepper-like spots but some of them have a completely black body. 

If you take a deep look at their heads, you will find a small cleft that makes it appear as a broken stem, again which is great for camouflage. In addition, their legs resemble that of long thorns that not only help in locomotion but also hide them completely in the tree bark. All in all, the Peppered Moth is the perfect agent in camouflage.

The Peppered Moth has a very distinctive look, and also shows similarities to a lichen. A lichen is a symbiotic relationship between fungi and algae that has a disoriented type structure found on many trees and plants. This unique characteristic makes the peppered moth look even more like a tree branch.

The Peppered Moth experience sexual dimorphism. The males have two, thick antennae with a feathery nature and are clearly distinguishable from the females.

They are not found in groups. The Peppered Moth is solitary and can be found alone on top of tree bark. It makes sense for it to be unsociable as its whole life is part of a disguise in camouflage. However, they may sometimes be found in pairs in the form of a female and male Peppered Moth. The male keeps close to the female to mark its paternity. 

As for its behavior, the Peppered Moth comes out at night and does most of its flying in the nighttime as well. It is safe to say that it is a nocturnal insect, hiding from its predators in the morning under disguise, and in locomotion at night.

Habitat: Where to find Peppered Moth?

They are found in various parts of the world but reside mainly in different parts of Europe. You can spot them in England, Ireland, Scotland, and the Northern parts of America. They are mainly found in shrublands and parklands. But some of their species can also be found in woodland forests. 

In these areas, their main site is the tree barks. Since they resemble a tree branch, they can easily disguise themselves as one of these tree barks. 

The Peppered Moths are usually seen flying around at night but during the seasons of May and August, they are seen together in pairs to mate and reproduce. The female can lay up to 2000 eggs in one reproductive cycle and these eggs can hatch into caterpillars within just two weeks.  

Evolution: What is the Story of the Peppered Moth?

It all started in the 1800s when the population of the famous white-colored peppered moth suddenly started decreasing. In 1811, there was a black peppered moth with no spots discovered. In 1848, the population of this black type of the moth suddenly started surging at a high rate.

The number of these species increased so much that by 1895, there was a record hit by the black peppered moths that outnumbered the light-colored ones by 98%. Later, it was realized that the sudden increase did not happen overnight but was a case of evolution.

In those times in England, there was quite a high rate of air pollution. This caused drastic changes in the evolutionary processes of the peppered moth, supporting Darwin’s theory of evolution. Although Darwin had died 14 years before this happened, this example was presented in support of his theory. 

The assumption made during those times is one that the white-colored moths would sit on top of the tree bark like they do in disguise. But because of the black soot in the atmosphere and the rising industrial pollution, the lightish peppered moths became a victim of genetic mutation.

In the later years, there was a decrease in the black peppered moths also known as melanic due to the genetic mutation. Again, this decrease was not unexpected. 

The black peppered moth is very vulnerable to its predators. It does not offer good camouflage and may be easily visible to the birds since it does not resemble any lichen. Hence, its breed eventually got eaten up by its predators, and there exist very few of them today. 

After proving the point of evolution, the peppered moth also supports the theory of natural selection. The black types were seen as larger in number in urban areas and cities. Since the tree barks were also affected by the air pollution, they also became black, offering the perfect disguise for the black peppered moths. 

Similarly, areas where the industries were not larger in number, witnessed a higher rate of the population of the paler peppered moths. This is because the environment in these areas suited the whitish peppered moths more. All in all, natural selection worked both ways. Hence proving that nature favored the best competitor respective of the environmental conditions.

Diet: What do Peppered Moths eat?

What does a Peppered Moth Eat?

The Peppered Moths are mainly herbivores. The caterpillars can be seen munching on tree bark and shrubs. In contrast, the grown moths can eat fruit pulp, leaves, flower nectar, and sometimes even plant seeds.

What Eats Peppered Moths?

Its predators are mainly flycatchers, nuthatches, and the European robin. The Peppered Moths protect themselves by hiding in the sunlight and traveling by night. They disguise themselves on the tree bark, remaining in one position to avoid their predators.

Similar Insects

Take a look at a few of our other articles on moths!

• Apple Moth
• Comet Moth
• Giant Leopard Moth

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2. Nature, Available here: https://www.nature.com/articles/hdy201292
3. Butterfly Conservation, Available here: https://butterfly-conservation.org/moths/peppered-moth
4. Britannica, Available here: https://www.britannica.com/animal/moth-insect
5. Wikipedia, Available here: https://en.wikipedia.org/wiki/Peppered_moth_evolution