Peppered moth

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Peppered moth
Peppered moth.jpg
Scientific classification
Kingdom Information
Domain Eukaryota
Kingdom Animalia
Subkingdom Bilateria
Branch Protostomia
Phylum Information
Superphylum Panarthropoda
Phylum Arthropoda
Sub-phylum Mandibulata
Infraphylum Atelocerata
Class Information
Superclass Panhexapoda
Class Insecta
Sub-class Dicondylia
Infra-class Pterygota
Order Information
Superorder Amphiesmenoptera
Order Lepidoptera
Infraorder Heteroneura
Family Information
Superfamily Geometroidea
Family Geometridae
Sub-family Ennominae
Genus Information
Genus Biston
Species Information
Species B. betularia
Subspecies B. p. betularia
B. p. cognataria
B. p. contrasta
B. p. fumosaria
B. p. nepalensis
B. p. parva
B. p. vlachi
Population statistics

The peppered moth (Biston betularia) is a species of insect of the family Geometridae, and found throughout much of Europe, Asia, and North America. The moth as found in Great Britain has been subject to repeated experiments and claims of hoaxes regarding the theory of evolution.


The peppered moth is a stout-bodied insect, about one inch in length, with a wingspan of about two inches. Like other moths (and unlike butterflies), the wings are held horizontally when at rest.

The normal coloration is a whitish or light-grey main background color speckled with black, hence the name. This coloration is referred to in scientific papers as typica; moths with more black than white are referred to as insularia. A melanistic all-black form is occasionally found, and is referred to as carbonaria, in part after the soot deposited by factories during the early part of the Industrial Revolution.


  • Biston betularia betularia
  • Biston betularia cognataria
  • Biston betularia contrasta
  • Biston betularia fumosaria
  • Biston betularia nepalensis
  • Biston betularia parva
  • Biston betularia vlachi

Life cycle

May to August is the breeding season for peppered moths, with adults on the wing during night hours. Females lay up to 2,000 eggs within the bark of trees, and the emerging young disperse on silk threads via the wind, landing on trees or other plants. They grow into two-inch caterpillars, feeding off the host plant by night; by day they rest motionless, blending in with the plant as a "twig". By September, they migrate to the ground and bury themselves in the soil, entering the pupal stage for the winter and emerging in the spring as an adult moth.

During the night peppered moths are predated on chiefly by bats, while during the day birds, such as robins and flycatchers, prey on them when they are resting within the tree canopy.

Evolutionary claims

An English naturalist named R.S. Edleston was the first recorded individual to identify a black peppered moth, writing in his journal in 1848: "Today I caught an almost totally black form of Biston betualria (peppered moth) near the centre of Manchester".[1] The area of Manchester in north-central England was part of a major creation and expansion of factories as the Industrial Revolution was in full swing. Providing the power for the machinery was coal, and it was the soot from coal burning that deposited on trees, turning grey trunks covered in mottled lichen black.

Since 1848 claims were made about the peppered moth confirming evolution. The basic explanation of this theory state the following:

  • The peppered moth prior to the Industrial Revolution was well-camouflaged against a similarly-colored background of lichen growing on tree trunks.
  • The melanistic black form - when resting against the same tree trunks - was easily picked-off by birds, and thus rare.
  • The depositing of soot blackened the trees, allowing the black form to be camouflaged, and the normal form to be predated on by birds.
  • Strict regulations enforced pollution controls in the later-19th century, gradually restoring the coloration of the trees, allowing normal lichen growth, and enabling the normal moths their previous advantage at camouflage versus the black form.

In the 1950s a researcher named H.B.D. Kettlewell did experiments concerning the two color morphs, expecting to see the black form picked off by birds when resting on clean tree trunks with the normal form untouched, and vice-versa when the trunks were blackened. Bats were not considered as a factor due to hunting the moths in flight with sonar, and not by sight. He concluded that "industrial melanism in moths is the most striking evolutionary phenomenon ever actually witnessed in any organism, animal or plant"[2]

Several scientists pointed out that the case of the peppered moth points out to natural selection, and not evolution, yet there are still many who tout it as proof of evolution. Overlooked and ignored in Kettlewell's experiments - and seemingly repeated by later researchers - was that some of the experiments were staged. To prove his theory that birds actively predated on the moths by color, Kettlewell needed to have the moths rest on the tree trunks during the day; the moths, however, rest normally in unexposed positions higher up in the tree, such as underneath leaves and branches where there is dark shade. To get them on the trunks, Kettlewell had taken dead moths and either glued or pinned them on. In his paper Michael Majerus also stated there were errors in the experiment, but still called for the subject to be taught in schools,[3] despite observed evidence that the peppered moth very rarely rests during the daytime on tree trunks, the primary reason for the theory in the first place.[4][5]

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