Why do caterpillars metamorphose?

[bloodline]

Bear in mind that the evolution of the Catapillar and the butterfly are independant.

Natural selection of one does not affect the other. This process allows the same set of genes to function in different environments. As Mel satates all insects have a descrete larval stage so clearly at some point their common ancestor developed this trait, and since it allows better use of of the resources. It was clearly an advantage and has persisted, some highly social insects undergo their laval stage while still in the egg. This makes sense since if you think about it.

(pick up a few Richard Dawkins books on natural selection and that should give you a clear idea of what's happening)

What is weird to think though, is that inside the catapillar are a few cells that do nothing, but have been their since it hatched from it's egg... then when the catapilla enters its cacoon, these cells then secrete enzymes that digest the rest of the catapillar... and the butterfly grows from these cells which feed off the catapillar... weird huh!

[bloodline]

motorollin wrote:

bloodline wrote:
What is weird to think though, is that inside the catapillar are a few cells that do nothing, but have been their since it hatched from it's egg... then when the catapilla enters its cacoon, these cells then secrete enzymes that digest the rest of the catapillar... and the butterfly grows from these cells which feed off the catapillar... weird huh!

Revolting :lol: Does the caterpillar die then?

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moto

well the butterfly cells are genetically identical to the Catapillar ones, and have always been part of the catapillar... so technically no...

[bloodline]

motorollin wrote:
I wonder why they evolved a larval phase rather than just laying bigger eggs with tiny, fully-formed butterflies inside?

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moto

Note that the larval stage often (though there are exceptions, see dragon flys etc...) lacks an exoskeleton, thus allowing the organisim to grow from a convenient birth size (i.e. the adult needs to lay 10's of eggs, thus they have to be much smaller than the adult) to a convenient adult size. Adults often do have an exoskeleton which is prety much set in size and unless the organism is able to molt (not something insects do, unlike spiders and woodlice etc...) then the adult is of a fixed size (the largest size the larva got to before metamorphosis).

[bloodline]

motorollin wrote:
Is it usual for moths/butterflies/insects to lay eggs whether they are fertilised or not?

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moto

If a fly doesn't lay it's eggs, they will hatch out inside the female and consume her.

Read Richard Dawkins, "Selfish Gene" for more info.

[bloodline]

CannonFodder wrote:

bloodline wrote:

motorollin wrote:
Is it usual for moths/butterflies/insects to lay eggs whether they are fertilised or not?

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moto

If a fly doesn't lay it's eggs, they will hatch out inside the female and consume her.

Read Richard Dawkins, "Selfish Gene" for more info.

Slightly OT here:  I just read Richard Dawkins "The God Delusion" it was very entertaining.  He's kind of a cross between Milli-Tant from Viz and Osama bin Laden, with a bit of Atheist2 thrown in for good measure. :-)

Yeah, the first few chapters are a bit "ranty" (which I found off putting, surprising given how much I have enjoyed all his previous books)... but once he gets stuck into the science, the book is really good! His best work by far is the "Extended Phenotype" though...

[bloodline]

motorollin wrote:

bloodline wrote:
If a fly doesn't lay it's eggs, they will hatch out inside the female and consume her.

Fascinating, but still,

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moto

The point I was making, is that the fly/insect/individual is irrelavant, all that matters is that the genes are passed on.

[bloodline]

motorollin wrote:
I understand that. I genuinely was fascinated by that, it was not a facetious comment :-)

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moto

No, I know! I'm excited by your thirst for knowledge, I felt it important to make that point. Please do read the "Selfish Gene"!

[bloodline]

motorollin wrote:
Intriguing...

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moto

As I understand it, this isn't possible... I'll have to read up some more...

[bloodline]

Speelgoedmannetje wrote:

motorollin wrote:
Intriguing...

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moto

That 'soup' comment made me think the catterpillar is an evoluted egg. (as these animals spawn as much eggs as possible, those eggs with the most capabilities can survive).

Inside a caterpillar there is a small bunch of cells that perform no function. Once the caterpillar has reached the desired size and spun itself into a protective cocoon, this small bunch of cells secrete a digestive enzyme that turns the catapiller into a nutrient protein soup... the cells then feed on the soup and grow into the butterfly.

That is the currently accepted method of operation. This research suggests this may not be the case. Since the currently understood mechanism treats each stage of the life cycle as independent organisms, no learned behaviour could be transferred.

[bloodline]

Karlos wrote:
It strikes me that it ought to be obvious that not all of the organism is broken down into nutrient, no matter how much digestive juices are released. Some component must remain intact. If it were not the case, surely there'd be nothing left to grow into the adult form :-?

See my post below :-)