Thread: Was having different stages (like an insect) a way to get on land?

I thought about why butterflies have that kind of complicated life cycles with an egg form, a larva form a puppet form and a butterfly form.
I had an idea but I don't know if it could be a proper explanation or if it is maybe common knowledge already.

My thought is that because the genes that transform animals in special life stages can be mostly found in insects and amphibia, and insects and after them amphibia have been the first animals who conquered the land...so is it possible that the whole transformation stuff was an adaption for life in habitats that include water and land?
Because unlike most of natures principles transformation don't seem to be the easiest solution. So...in my opinion all the complicated transformation stuff must at least root in something that has been an easy solution.
Was the problem to live on water and land?
So...instead of being able to live on land and water at the same time (like mudskippers, frogs, cancers, penguins) is it possible and plausible that the first steps on land where made by mutations that allow you to spend your second half of your life on land? (like gnats)
But there are a few problems:
If I'am not wrong insects are descendants of cancer-like animals...and cancer (at least the modern ones) don't go threw different stages at all (at least as far as I know)
Is it possible that animals form pure "land-organs" (like wings) in a stadium before animals who are only land animals, evolved that organs? So have water living animals developed "land-modus" or have Land animals found an advantage to let their kids be born in a liquid environment? (If the last thing would be the case than my theory would be wrong)
And I don't really understand why and how animals came from having one stage, to having many. That would be like having fins as a kid (not as a fetus) and having legs as a grown up. And all adaptions to water of younger animals like reptilian, mammals, birds are based on the "being-able-to-live-in-both-habitats-at-the-same-time-approach" and slowly modify your organs in one or another direction. Maybe it's because I'am a mammal, but that seems to be much easier and much more logical but I can't deny that there animals who lived on land longer than us (insects) who seem to not have chosen that pass.
I would be glad if you could help me with my problems or at least tell me why and how I'am wrong.
Thank you.

Originally Posted by Headdresser

I thought about why butterflies have that kind of complicated life cycles with an egg form, a larva form a puppet form and a butterfly form.
I had an idea but I don't know if it could be a proper explanation or if it is maybe common knowledge already.

My thought is that because the genes that transform animals in special life stages can be mostly found in insects and amphibia, and insects and after them amphibia have been the first animals who conquered the land...so is it possible that the whole transformation stuff was an adaption for life in habitats that include water and land?
Because unlike most of natures principles transformation don't seem to be the easiest solution. So...in my opinion all the complicated transformation stuff must at least root in something that has been an easy solution.
Was the problem to live on water and land?
So...instead of being able to live on land and water at the same time (like mudskippers, frogs, cancers, penguins) is it possible and plausible that the first steps on land where made by mutations that allow you to spend your second half of your life on land? (like gnats)
But there are a few problems:
If I'am not wrong insects are descendants of cancer-like animals...and cancer (at least the modern ones) don't go threw different stages at all (at least as far as I know)
Is it possible that animals form pure "land-organs" (like wings) in a stadium before animals who are only land animals, evolved that organs? So have water living animals developed "land-modus" or have Land animals found an advantage to let their kids be born in a liquid environment? (If the last thing would be the case than my theory would be wrong)
And I don't really understand why and how animals came from having one stage, to having many. That would be like having fins as a kid (not as a fetus) and having legs as a grown up. And all adaptions to water of younger animals like reptilian, mammals, birds are based on the "being-able-to-live-in-both-habitats-at-the-same-time-approach" and slowly modify your organs in one or another direction. Maybe it's because I'am a mammal, but that seems to be much easier and much more logical but I can't deny that there animals who lived on land longer than us (insects) who seem to not have chosen that pass.
I would be glad if you could help me with my problems or at least tell me why and how I'am wrong.
Thank you.

I too find complete metamorphosis fascinating. In response to your question I found this article from Scientific American, which is worth a read:

How Did Insect Metamorphosis Evolve?: Scientific American

It says nothing about the transition from water, which did not surprise me, as I suspected most early insects underwent incomplete metamorphosis, i..e. an extension of moulting - which after all is what water-dwelling arthropods such as crabs and lobsters do. It looks from the article as if nobody really knows, but the suggestion is that complete metamorphosis may have been an extension of the pro-nymph -> nymph transition undergone by some insects that make an incomplete metamorphosis.

Perhaps Adelady or some other knowledgeable person will be able to add more......

Fascinating. I have watched dragonflies emerge from the nymph stage and never noticed the obvious difference from a butterfly's pupal stage.

And three new words: ametabolous, hemimetablous and holometablous.

Originally Posted by Strange

Fascinating. I have watched dragonflies emerge from the nymph stage and never noticed the obvious difference from a butterfly's pupal stage.

And three new words: ametabolous, hemimetablous and holometablous.

I find the weirdest thing is the degree to which the actual cells of a holometabolous larva break down and then these embryonic things called "imaginal discs" (from "imago" - the adult, I suppose) start growing in the dissolved tissue and make what is virtually a new creature. It is almost as if the caterpillar dies and becomes the egg medium for the imaginal discs to grow in, creating the adult. Reincarnation! I know it is not really quite as extreme as that, but not far off. It must rank as one of the most peculiar processes in the animal kingdom - seen from the viewpoint of a mammal, at least.

Originally Posted by Headdresser

Was having different stages (like an insect) a way to get on land?

A very nice hypothesis! Is it yours, or did you hear/read it somewhere?

I don't know the evolutionary history of insects. Does anyone know if insects/proto-insects evolved to multi-stage lifeforms around the time amphibians/proto-amphibians began crawling out of the waters. I think this would be a clue, as environmental pressure may have acted on both evolutionary lines simultaneously.

Originally Posted by jrmonroe

Originally Posted by Headdresser

Was having different stages (like an insect) a way to get on land?

A very nice hypothesis! Is it yours, or did you hear/read it somewhere?

I don't know the evolutionary history of insects. Does anyone know if insects/proto-insects evolved to multi-stage lifeforms around the time amphibians/proto-amphibians began crawling out of the waters. I think this would be a clue, as environmental pressure may have acted on both evolutionary lines simultaneously.

Suggest reading the article I referenced in my first reply to the OP. I think complete metamorphosis is thought to have arisen later.