How Does Bug Soup Become a Butterfly?

How Does Bug Soup Become a Butterfly?


You’re probably familiar with the basic
life cycle of moths and butterflies: an egg hatches into a caterpillar, which becomes
a pupa, which then transforms into a fully-grown moth or butterfly. But that transformation isn’t easy: if you
sliced open a pupa at just the right point, you’d find nothing but bug soup. Caterpillars grow the beginnings of their
adult body parts before they even hatch. They have these tiny clumps of cells called
imaginal discs spread around their bodies, and during metamorphosis, each disc develops
into a different part of the adult butterfly or moth. When a caterpillar becomes a pupa, it releases
enzymes that dissolve almost all of its tissues. Only the imaginal discs, plus certain muscles
and portions of the nervous system, survive. The rest of its body basically melts into
goo. This protein-rich slurry helps fuel an explosion
of new cell division, as the imaginal discs grow into full-fledged wings, eyes, and legs
for the adult insect. But even though they almost totally dissolve
and rebuild themselves from scratch, adult moths /can/ actually remember things from
when they were caterpillars. In one study, researchers gave mild electric
shocks to tobacco hornworm caterpillars, a type of moth, while exposing them to specific
smells. After metamorphosis, the adult moths still
avoided the smells they’d learn to associate with unpleasant shocks. So at least some of the caterpillar’s brain
seems to stick around through metamorphosis, even as most of its body dissolves. Even though metamorphosis is a complicated
process, we know that it’s helpful for insect species. The total rearrangement of body parts means
that adults and young can rely on different food sources. Usually caterpillars eat leaves, while butterflies
and moths specialize on nectar. Preventing different life stages from competing
for the same resources gives these insects a big evolutionary leg up. We’re still not entirely sure how metamorphosis
evolved, though. One theory, which has since been discredited,
suggested that metamorphosis became a thing when an insect that flew and an insect that
crawled happened to mate. Instead, it probably evolved gradually from
less-complicated forms of development. No matter how metamorphosis evolved, it does
make moths and butterflies super hardcore. They might look delicate and pretty, but those
critters dissolved their own /bodies/ and survived. Thanks for asking, and thanks especially to
all of our patrons on Patreon who keep these answers coming. If you’d like to submit questions to be
answered, or get some videos a few days early, go to patreon.com/scishow. And don’t forget to go to youtube.com/scishow
and subscribe!

100 thoughts on “How Does Bug Soup Become a Butterfly?”

  1. have we ever been able to observe metamorphosis directly like through an artificial transparent cocoon or a genetically engineered bug that produces a transparent cocoon?

  2. Every SciShow QQ:

    "Here's the question you asked with a catchy title and thumbnail which makes it seem like we're about to answer your question.

    The answer? Fucked if I know. Nobody knows. Scientists have no idea.

    Please support us on Patreon, kthxbye."

  3. I asked this question like 2 years ago. Not quite was I was looking for in my original question I don't think but it's incredible that they can remember things from before the transformation.

  4. this is one of Olivia better presentations, although there's still a little bit where her voice goes down and crack at the end of isn't as prevalent or irritating as before. on the other hand I come to notice that her s hiss are pretty loud, maybe try to work on that next like trying to use less force on the s.

  5. Woah i never even knew about the "bug soup" thing in the first place. Really goes to show that what seems to be the simplest thing can have more to tesch you.

  6. Aren't humans pigs during early fetal stages? I've heard they look like pigs so that must means for a short time humans are pigs. Then they grow into humans and then back into pigs. It's very fascinating really.

  7. Oh, man. I've actually been wondering about this for years and somehow never looked into it. Thanks for answering!

  8. A caterpillar dissolving itself sounds painful, but thinking about evolution, it would make sense if it wasnt. If instead it actually triggered a reward of many good feelings, which would encourage the transformation, leading to greater success of the species. This is in the exact same way that intercourse is pleasurable. How long do you think the human race would last if sex was painful?

  9. I think you make a great Sci show host, but I have some constructive criticism. I think you need to work on dropping the upward inflection? It really hurts your credibility? It makes you sound like you're still like totally in high school? Otherwise well done.

  10. Can someone explain me what a moth is for anglophone people? In France we say butterfly and night butterfly for the kind she saw when showing a "moth", and moths are a little species of white night butterflies that's known to feed or live (don't remember) in clothes and mostly in flour, and is known into the popular belief for that reason.

  11. Very interesting, I always kind of assumed that the cells more changed and rearranged themselves than outright melted into goo and regrew completely. Also, you looked nice in this episode, Olivia. I appreciate the effort.

  12. the mad scientist in new wants to know if you can make siamese butterfly twins by injecting one cocoon's goop into another? I have many other questions about stuff if anyone there would like to hear more of.

  13. "One theory, which has since been discredited, states that [cartoonishly nonsensical rambling here]."

    Sure, let's make this a regular feature of this science channel, why not? 😉

  14. Tobacco Hornworm caterpillars. Do they live in Michigan? I was told they were called tomato worms.
    I've seen them on my mother's flowers before. They're nasty little bugs. They leave huge piles of grenade-shaped poop, they demolish leaves and multiply like crazy.
    Not to mention, they don't just let go if you try to pull them off. I could only seem to get rid of them by killing them 1 by 1 with a BB gun.

    They kindof explode into a giant dark green booger.
    Just sharing my experience with the worm at 1:15

  15. ok is this girl going to be in every vid now? Maybe I didint see all of scishow vids recently but where is hank?! give me hank back plz!

  16. Could their "memories" actually be genetic tags we discuses some time ago with mice that were given a shock as well passed the trait on to their children?

  17. This is ABSOLUTELY fascinating! I never knew this. How did I never know this?
    SO does the brain dissolve as well or is the brain considered one of those functional cell/protein discs?

  18. Does this girl annoy the shit out of anybody else or is it just me and my roommates? I don't understand why they keep featuring her so heavily. Go back to strictly Hank Green and Michael Aranda.

  19. I'd heard about the goo-ification of the caterpillar, but not about the possible evolutionary history. That's bugging me out!


    I'll see myself out.

  20. So when an insect becomes bug soup in its pupa, does it "die"?
    Meaning does the instance of life that the larva was cease to be for the duration of the metamorphosis, only to have its biomass repurposed and reconstructed to become another instance of animal life?
    The whole thing is so foreign to us non-insects that it's tough to even articulate the idea, but what I'm getting at is that is a larva a completely different being than the adult?

  21. It would be interesting to see if the moths' offspring also avoided the smells their parents associated with unpleasant shocks.

  22. The origin of this two-stage process can be seen today. To survive over the winter, modern caterpillars create cocoons and hibernate. Some species emerge from this hibernation as mere caterpillars. Others emerge as butterflies. At some point in history, caterpillars found they could change small features over the winter to better prepare for the spring vegetation, which differs significantly from fall's vegetation. Bit by bit, these small changes became so numerous that a post-hibernation caterpillar could no longer be considered caterpillar… but something else entirely. A butterfly.

  23. I didn't know insects can learn like it's suggested here. I don't know how that sits with me, I'm kind of comfortable with my wievpoint that insects are sort of nature's answer to robots.

  24. can imagine being the first caterpillar going through this
    "Hay ya Jim ,WTF are you doing there"
    "IDK , i just really felt like wrapping myself in this silky shit"

  25. My theory: metamorphosis evolved from premature hatching. Wherein the not fully developed animal was forced to forage for additional food to reach adulthood, temporarily pausing growth until it had enough resources then using it all up in one go to reach the final reproductive stage. It's mirrored in amphibians as well, where tadpoles are born before limbs are formed. It would also explain another phenomenon – neoteny. Wherein the animal never reaches the adult form at all.

  26. So, the body is dissolved into goo and re-created into a completely different form, selectively preserving just the nervous system and a few other bits. Fascinating! Metamorphosis is a complicated and amazingly designed process that is currently far beyond our understanding.

  27. 500 years in the future: A member of a space crew lays down in a tight artificial birth already inlaid with photosynthetic skin. It closes as a large machine slowly lowers onto the birth. Sedative, then minutes later adapted butterfly enzymes flood the chamber. The machine will replace his digestive and respiratory tract with a larger set of lungs. Nanites correct damage to the lenses of the eyes and other space deterioration. As he develops many of the soft tissues are regrown, especially muscle tissue via steroid administration. In one month the man emerges with no need to eat and a decrease in oxygen requirements. A technician checks him over. "Feeling ok?" "Sticky but fine. I hate that these things ware out after 6 months though. Replacement sucks." "Don't worry we'll grow you back a …. normal hairy one, once we get there, they last forever."

  28. Does the bug soup have to be in the cocoon? Could it be in a container or something where we could see the transformation.

  29. So, by the sounds of it, caterpie should need to know Acid Armour before it can evolve.

    Also, I've been wondering about how melting yourself and rearranging your own body could turn up gradually. I'd be interested to know if that ever does get figured out. That and frog metamorphosis. And bombardier beetles' blasting.

  30. There's a chapter of the manga Franken Fran that prominently features a human going through metamorphosis. A high school girl gets crushed by a car, and in order to save her, Fran uses insect/human hybrid DNA to give the girl a body like a giant caterpillar. The girl cocoons up after a while, and emerges from the chrysalis with a normal human body again.

  31. So…they dissolve their entire body, but still retain their old memories?
    THE DOCTOR IS A BUTTERFLY: CONFIRMED. XD

  32. I think the reason butterflies undergo metamorphosis is because the species is evolving, and their current stage is the "in between" stage

  33. You didn't answer. You could have similar said, "I don't know". Science hates to admit they know nothing

  34. “They seem to remember things from when they were caterpillars!”

    Well duh, haven’t you ever raised a Caterpie? They still know Tackle and String Shot once they’re fully evolved. 🙄🙄🙄

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