Natural Selection And The Case Of The Peppered Moth

Natural Selection and the Case of the Peppered Moth

If you're anything like me and you spend a lot of time talking about Interesting Facts and Things to anyone who will listen, you may have heard a slightly warped account of the story of the peppered moth. Maybe someone said something like: "Oh yeah and in England there was this moth that turned black during the industrial revolution due to all the coal dust in the air". Which is... not exactly true.

Let me start the story from the beginning. Before the industrial revolution, peppered moths (Biston betularia) were distributed across England, Europe and North America. They existed in 3 morphs: typica (mostly white), carbonaria (mostly black) and insularia (inbetween). Note: I'm mainly going to talk about the typica and the carbonaria morph here.

Before the industrial revolution, the typica morph was the predominant morph. Peppered moths lived in forests filled with light trees and lots of lichen, a good place for a typica morph to blend in. The carbonaria morphs were living life on hard mode, though. They did not blend in, and were more easily picked out by predators like birds. Below you can see how well a typica morph blends into lichen.

Then the fire nation attacked. Jk, then came the industrial revolution. Factories were pumping out coal fumes into the air, covering forests nearby with coal dust and killing the lichen that grew on them. In these forests, the carbonaria morph blended in better. Predators began to pick out typica morphs more often. And so, carbonaria morphs became the predominant morph in forests near industrialized areas.

Naturalists, noticing this, wanted an adequate answer on why this was happening. In the 1950s Bernard Davis Kettlewell used various methods to test the hypothesis that it was natural selection. And indeed it was. Typica morphs were 2x more likely to be eaten in a polluted forest than carbonaria morphs, and vice versa.

This phenomenon was so common, and observed in many other moth species across industrialized areas, that it was even given a name: industrial melanism.

So there you go. The full story of the peppered moth :)

Oh and I should add that in areas where the effects of industrialization were reversed, the typica morph once again becomes more common.

Sources:

Peppered moths: moth life cycle

Peppered moths: natural selection

Peppered moths: dr ketllewell

Love love love these spaceship lookin silly guys

Image source: x

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Is the atlas moth really the biggest moth out there? (spoiler alert: there are different ways of measuring 'big')

Largest by wingspan - the white witch moth:

Wingspan: around 30 cm max

Fun fact: despite its large size the eggs, pupa and caterpillars of this moth remain undocumented. Check out the white witch watch for more info.

Largest by wing area - the female hercules moth:

Wing surface area: 300 square cm

Largest by weight - the female giant wood moth:

Weight: 30 g max

Largest overall - the female atlas moth:

Wingspan: largest recorded 30 cm

Wing area: 157 square cm, according to this site, which doesn't cite any source for that info

Although it's listed in the guiness book of world records as the largest moth, I'm confused as to why that is. The wingspan of the white witch moth is bigger, and the wingspan of the hercules moth is bigger, according to Insect Biodiversity: Science and Society by Robert G. Foottit and Peter H. Adler. The wing surface area of the hercules moth is also bigger according to Amazing Numbers in Biology by Rainier Flindt.

Note on conflicting information: Many of the general use sites I happened upon while trying to find sources closer to the primary source incorrectly quoted this article, sometimes saying Attacus caesar has the second largest wingspan of all moths, and sometimes incorrectly quoting the atlas' moth wingspan as 24 cm or 27 cm when it was 262 mm/26.2 cm in the original article. In my opinion, the atlas moth can't rightfully be called the largest overall moth, but it does hold the record, with the largest wingspan recorded being 30 cm (in the guiness world record).

Image sources:

[1] [2] [3] [4]

Information sources:

White witch wingspan

Hercules moth wing surface area and wingspan

Giant wood moth weight

Atlas moth

there's an end in friend.

there's an over in lover.

there's hell in hello.

there's a lie in believe.

but father and mother?

that's where you find fa(THE)r (MOTH)er.

PSA: don't pick up random spiky or hairy caterpillars

A lot of them have urticating hairs, which really itch when embedded in the skin and can cause further damage upon ingestion or contact with mucous membranes. Sometimes caterpillars' hairs or spikes are filled with venom which is released into your skin on contact and can hurt like hell and even cause respiratory problems, in the case of southern flannel moth caterpillars (Megalopyge opercularis), picture of one below for reference:

And, in the case of Lonomia obliqua caterpillars, these hairs can even cause internal bleeding and death (with a horrifying death rate of 2,5%). Picture below:

I know, they're cute. But it's not worth it.

Image sources: [1] [2]