By what process does a caterpillar change into a butterfly?

April 28, 2008 5:18 PM

How does the caterpillar become the butterfly (why does one part of the chrysalis know to become a leg, and another a wing)? Is it as simple/complicated as the cell division of a human fetus? Does the transformation of this jelly into a butterfly occur from the head down, or all at once? Anyone?

Not that it's necessary, but I just thought I'd say that this question has been bugging me for quite some time. Everywhere I look they talk about the "breaking down" of the old cells and the "reforming" of the new. Are the cells completely broken down or just rearranged? What controls the process? Is there any part that is not at all broken down, across the many types of butterfly? You should know I am not a biologist, but am happy to research any terms you use in your answer. I would, of course, prefer it in layman's terms... (thank you in advance)

posted by omnigut to science & nature (11 answers total)

Genes exist that control development in butterflies and humans, including the development of legs and wings (for the butterfly, that is). I don't know the names of the genes in question for the butterfly.
posted by cahlers at 5:48 PM on April 28, 2008

The process is called Metamorphosis, for the nitty gritty cahlers has you covered.
posted by BobbyDigital at 6:02 PM on April 28, 2008

According to Wikipedia:

There are two main types of metamorphosis in insects, hemimetabolism and holometabolism....In holometabolism, the larvae differ markedly from the adults. Insects which undergo holometabolism pass through a larval stage, then enter an inactive state called pupa, or chrysalis, and finally emerge as adults. Holometabolism is also known as "complete" and "complex" metamorphosis. Whilst inside the pupa, the insect will excrete digestive juices, to destroy much of the larva's body, leaving a few cells intact. The remaining cells will begin the growth of the adult, using the nutrients from the broken down larva. This process of cell death is called histolysis, and cell regrowth histogenesis.

For more information specific to butterflies, check out this page.
posted by jedicus at 6:10 PM on April 28, 2008 [2 favorites]

It is actually not clear. So far, it looked like as you said, there is a complete break down of the cells during the Metamorphosis and any part of the Butterflies Remember What They Learned as caterpillar could become any part of the butterfly.

But, it may not be the case because recent research shows that
butterflies remember what they learned as caterpillars.

This would mean that at least some cells that are part of the neural system are in fact not broken down and keep their functions during the metamorphosis phase.
posted by McSly at 6:12 PM on April 28, 2008

Thank you all, your answers have really helped. However, is there anyone out there who would know what cells are left intact, and where they might be in the chrysalis? Thanks!
posted by omnigut at 6:15 PM on April 28, 2008

Simplified overview:
1) The caterpillar and the butterfly are for the most part made of different cells.
In the embryo, certain cells are set aside that will develop into adult structures, whilst the rest of the cells go on to make the caterpillar. The cells that were set aside form structures called "imaginal discs" ("imago" being a term for the adult stage), and they undergo their own developmental program inside the caterpillar. Inside the chrysalis, these imaginal disc cells replace the caterpillar cells.
2) Positional information is provided to cells in the embryo, and informs subsequent development.
When the mother butterfly lays her eggs, they already have in them proteins that are positioned in particular places to define which end is the head and which is the tail, and which is the dorsal (back) side and which is the ventral (belly). This system of axes allows each imaginal disc to "know" where it is in the animal, and this information influences the development of the cells in the disc so that they form structures appropriate for their position.

This book might interest you.
posted by nowonmai at 6:26 PM on April 28, 2008 [3 favorites]

Some links to get you started on further reading:
Imaginal disc on wikipedia.
Homeotic genes help to specify what part of the butterfly each imaginal disc forms.
posted by nowonmai at 6:42 PM on April 28, 2008

Regarding the cells from the caterpillar that persist in the adult: many neurons persist, but the connections between them are extensively remodelled. Certain internal organs also persist, such as the Malphigian tubules (analogous to kidneys).
posted by nowonmai at 7:08 PM on April 28, 2008

There's a good explanation and some rather astounding pictures over at wormspit. Of course that's a moth. But what it shows is that under the skin of the pupa it's not as chaotic as it seems. This becomes that. While often described as a jelly that re-organizes it's not that random.
posted by Toekneesan at 7:32 PM on April 28, 2008 [8 favorites]

Holy crap, Toekneesan, that wormspit site is amazing. Thanks!
posted by peachfuzz at 7:58 PM on April 28, 2008

Thanks to Toekneesan for pointing to my site! There are some better photos of the intermediate stage, HERE about 3/4 down the page. I know that a lot of the caterpillar's body dissolves and re-forms, but it's certainly not "just goo" inside. By the time it slipped off its caterpillar skin, this pupa already had distinct buds that would become wings, legs, abdominal segments, etc. I was quite surprised to see that the wings and legs were separate at this point, and then stuck down to the pupa afterward; I had always thought they were inside a solid shell that didn't alter.

It's my understanding from my reading, that many of the parts stay the same - eyes are still eyes, legs are still legs (although the caterpillar prolegs go away) and many of the muscles remain muscles.

Of course, these are MOTH images, not butterfly - but I'm betting that the process is very similar, just with a chrysalis instead of a cocooned pupa.
posted by WormSpit at 7:59 AM on April 29, 2008 [1 favorite]