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Comment by flippyhead | Hacker News Reader

Slightly off topic but I always wondered why at least some spiders never developed wings/flight. They do so much other crazy stuff!

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Some of them do! Fly at least... https://en.wikipedia.org/wiki/Ballooning_(spider)

I thought that a possible way to answer this was to analyze how insects developed flight, and try to understand the differences, and hope there is something enlightening.

The problem is that we don't know ... https://en.wikipedia.org/wiki/Insect_flight#Evolution_and_ad...

This is a bit like asking why bats never evolved the ability to spin webs.

Evolution strongly favors initial conditions, and doesn't tend to come up with major changes in bodyplans once something is established.

But insects have a crazy variety of body plans precisely because their basic setup lends itself to a lot of diversity in a way that, say, our body plans do not. Something to do with having exoskeletons. Spiders seem a lot closer to insects in this way which (to me at least) begs the question..

There tends to be a lot of variation within a certain set of initial conditions. E.g. all insects have 6 legs & three body segments, whereas spiders have 8 legs and two body segments.

This isn't only true in the pedantic sense in relation to your question, i.e. if you did have something evolving from insects that say added an extra pair of legs it would be a new class of arthropods, so it wouldn't be an insect anymore, but nothing major like that has branched off either insects or spiders.

Insects evolving 4 sets of legs would be a much smaller change than spiders evolving wings, since insects already have all the genetic material to grow legs, but spiders have none of the genetic material to grow wings and would have to independently evolve them.

As an aside you're misusing the term "begs the question", it doesn't mean "prompts a question", it's a reference to a specific logical fallacy that doesn't apply here.

Could the wings be considered another set of legs? So they either have 4 pairs of legs, or 3 pair and a pair of wings.

I think that insect variations are due to very short lifespans with high reproductive rates and a more simple design.

I just made the following calculations: fruit flies for example live 50 days, this accounts for more than 500 generations during a typical human lifespan. They lay up to 500 eggs. Of course survival rate must be very low but just for the fun of it let assume everyone survives (maybe a natural disaster has eliminated predators). This means that during the time evolution has tried 10 new human designs it can try also on the order of 10^1300 new fly designs (500^500).

Don't just go throwing around exponentials like that. That would be more fruit flies than could fit in all volumn of the visible universe. Most die, thank god. Little jerks after my fruit.

Oh god what if centipedes developed flight. A dozen sets of wings all down the body. Aaargh.

Butterflies.

(To a rough approximation.)

Any Latin speakers? Centiala? Centialae?

Centiptero sounds better. Ptero as in pterodactylus.

(Yes, it's mixed Latin-Greek, but so are metadata, hypervisor and hexadecimal.)

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