The Truth About Butterfly Metamorphosis (It's VERY WEIRD) 

Could you imagine if humans did this? "I'm sorry, but Johnny can't come to school today. He's locked himself in his room, and isn't coming out for the next two weeks." "That's exciting, Mr. Smith. I'm sure your whole family is very proud. Please remember that when he does emerge, he will be expected to make up the work."

Preschool teacher: And from within the fat little caterpillar burst a writhing mass of wasp larvae that ate the caterpillar from the inside out and grew up and laid their eggs inside more caterpillars!

Small correction towards the end: flies don't do the metamorphosis IN rotten meat or poo, they tend to stop eating and craw away from food to pupate (otherwise the adult will immediately drown as soon as they eclose). I worked with both fruit flies and blow flies in the past and you always find the pupae far away from the food.

I feel like one factor for metamorphosis is energy - the amount of energy required in the egg to create a pupal stage vs a more complex adult. The pupal stage means the mother can expend a LOT less energy and instead make hundreds or thousands of eggs that then acquire their own energy. But im an engineer - its always energy XD

Big and important correction: moths don't spin a silk cocoon INSTEAD OF becoming a hard-skinned pupa; they do it BEFORE becoming a pupa. Cut open a moth cocoon, and there's a pupa inside it. Also, cicadas are mentioned in the same breath as beetles, but cicadas don't have a pupal stage; they're hemimetabolous. They go straight from nymph to adult.

When I finish writing/illustrating "The Very Hungry Maggot", I'll expect you to review/endorse it. Love your work.

You've brought back a memory from my 5 yr old self where I squished a cocoon to see what it was all about. I buried the pulp and cried.

If you keep in mind that during the chrysalis stage that hard shell on the outside was once the exoskeleton of the caterpillar before metamorphosis, it makes sense that it has protowings and such.

Imagine parents consuming all the resources in an ecosystem and blaming the children for not having enough.

The butterfly wings are kinda like our 2nd set of teeth.. already there but just under the surface where we can't see it.. pretty cool

I’m genuinely surprised the chrysalis is inside the caterpillar and they just reveal it. Somehow more disturbing.

"This isn't kids book stuff, this is more like Silence of the Lambs." I wonder how Joe teaches his kids about the facts of life😂

My sibling worked at a neurology department in their moth lab. They used the metamorphosis of sphinx moths to study neural development!

I have a fear of butterflies and am trying to reduce it gradually by exposing myself (virtually) and learning about them. This was really cool to watch :)

It seems to me that caterpillars are just a second stage of embryonic development, but external and more autonomous. Since the egg does not have enough nutrients, they must eat to continue their development. Once they secure enough food, the final transformation is done.

I raised a monarch from caterpillar to butterfly last year, it was fascinating seeing them change. The end of the period they are in the chrysalis it turns clear

I haven't thought about this in 10+ years, so thinking about it seems like magic how a bug turns into a butterfly

Couple years ago I had a cabbage white in my living room and let it out. More than half a year later I found its crysalis hidden behind the door inside of my fridge, where it apparently ended up as caterpillar with the groceries. Despite the cold, it pupated and eventually hatched. I also found another one next to it, which didn't hatch yet, I could feel it bobbing around carefully shaking the crysalis. I assumed it dead, took both crysalises out and ordered some resin, colours and tools to make fake amber earrings with the crysalises inside. After a week of lying on a table in the warm living room, while I was waiting for the supplies, the 2nd one miraculously did hatch as well. I guess the cool environment inside the fridge basically told it to lay dormant and wait for spring before hatching, which then it did. I was amazed.

I feel like the butterfly goo myth originated when somebody tried to open a pupa to look, its guts came out, and they just went "Welp I guess that's all there is in there!"

We had a bunch of caterpillars for a school project. Some metamorphosed just fine, some died before they had the chance, and some seem to never make a chrysalis and just turned to goo? We never found bodies but there was goo.

I know multiple people who are scared of insects, even “pretty” and harmless ones like butterflies, despite not having bad experiences with them. I’m sure you have a video posting schedule but it would be neat to explore what draws out the natural fear of these things in a future video :)

As a matter of fact, no we didn't raise any butterflies in school. HOWEVER. The school I attended for 3rd grade and 5th grade (don't ask, Midland Texas has WEIRD school district lines) had a "caterpillar problem." Every year in spring there would be absolute hordes of itty slightly fuzzy pale green caterpillars, all over the ornamental plantings but also all over the walls!! A lot of the kids were freaked out by them but I was always fascinated since I knew they weren't going to bite or sting me, and finally one day in 5th grade, I caught one of the caterpillars and very carefully brought it home with me. My mother did not flip her lid, and instead gave me a glass jar to put the creature into, and told me to go outside and pick three stems off the ornamental bushes in the apartment complex, but ONLY the ones that looked just like the bushes at the school. (At that age I already knew my mother was smart, never even questioned it, ha) She fixed up the jar so that the caterpillar couldn't easily crawl out, and we gave it its food and it was chill! I would get it onto my finger for a few moments every day just because I could, and I'd bring home a new stem every day with more leaves. Then - the weekend. Saturday morning - and my caterpillar had vanished!!! I looked high and low (well, as "high" as a nine year old can look) and couldn't find it. Very sad. But SUNDAY morning I saw the pupa!! The caterpillar had managed to get out of the jar and made its little sack of magic on the curtain. Few days later - and there was a moth!!! A beautiful white moth with vivid tiger-orange on the inside of the wings. And though I know now as an adult that bugs don't exactly bond with anything or anybody, it seemed to me like the moth remembered me, and it flew over and landed on my shirt and just kinda sat there like "Welp. Outside now, please." So of course I took it outside, set it carefully on a bush, and watched it fly off to do whatever moths do. And at the school? Dozens and dozens of white-and-orange moths on Monday! So many! The grownups were all super annoyed but to me it was pure magic. To this day I have no bloody idea what kind of moth it was though. I've never found ANY picture that looks like my moth pal.

I think you missed out on the most interesting aspect: Butterflies remember things from their caterpillar days. Let me remind you they turn into insect goop while inside the chrysalis and then re-assemble.

I wonder, did all these genera of pupating insects independently evolve their pupating strategies, or did they diverge from a common ancestor only after it adopted the pupating strategy?

This is super interesting. Also a bit more approachable but on par in weirdness is that an egg containing of inconspicuous white and yolk that probably each of us ate on breakfast at some time... consists all ingredients to make a whole small bird. Given the egg is fertile it contains all the resource and bioengine to transform it into a bird, from some bio-mush. In that sense it's like chrysalis.

Not just cannibalistic caterpillars. I had some shaped like inch worms preying on aphids, on some umbelliferous plants one year.

Heh I taught myself that chrysalis are just another layer under the skin while reading my own caterpillars. Also moths do the the same, they just do it inside the cocoon. Certain ones like the gypsy moth will even just make a super lazy cocoon, just folding a leaf partially together.

School taught me the version of Caterpillar -> Chrysalid -> ? -> Butterfly. I'm 33 and I'm ashamed of myself for never actually questioning "Huh, what does really happens to that caterpillar once inside"

It's a little more horrifying to know the foundational elements of the butterfly are developing within the whole time. Its less you assuming a new form, and more your existence is fueling this second lifeform eventually taking over. Like it started with a parasite and they linked life cycles.

I got up close and personal with some butterflies while camping and even as an adult it’s just such a joy to see them! It’s like a welcome visit from a friend, and I always talk to them as they fly by. I’d always wondered what went on in there 😊

Hi Joe, Bob here. Another amazing show. I also used to catch caterpillars and watch them pupate and emerge as butterflies. It was fascinating. And still is.

13:54 Joe talking with his hand shaking the chrysalis back and forth 😂I was like, "you're going to shake it off the branch!" imagine the pupa going "ohmygod everything's shaking it's the end of the world!!!!!!"

One further interesting tiny point that I find fascinating and inexplicable is the very small period of time when the chrysalis, if it is one that hangs downward from the tail (not all do, some are suspended upward with a silk waistband, some are in cocoons such as with moths) has to shed the skin of the final instar of caterpillarness, which becomes a crinkled up bundle, and then the chrysalis (blind) has to walk with it's tail hooks (which are like hook&loop fastener) across the drying bundle of shed skin, and onto the silk pad onto which it hooks and stays - that’s not only amazing it can do this every time, but that it has ‘knowledge’ to do this specific one-time action, and seriously, how did that evolve, there must’ve been so many that fell off and didn’t survive? That’s certainly one for Darwin if you ask me

i love how much comedy effort is put into making into all of yours videos

Cool. Suggestion: for shots that are sped-up or slowed down, always add the speed in the corner (like "x100 speed"). It's science communication after all. Thanks.

Omg I didn't know scientists had figured this out. The last thing I heard (long time ago) was that it wasn't known what happens. I always wanted to know this. Thank you so much!

Well over 15 years ago as a child I would bring this up to family and teachers that I believed the inside of a chrysalis was liquid and I wanted to order some caterpillars and open them up mid metamorphosis to prove my theory.So you better believe I was so excited to learn the truth about them when I got older

Eric Carle fan. He actually wanted to write a book about a bookworm. His publisher or editor wanted the change. He just wanted to make a book with fun holes in it. A lot of his books have fun tricks to them.

Thank you so much for this video! A few times now I've gotten really curious on what exactly is going on inside a chrysalis but had never been able to find anything remotely detailed enough. This not only provides some good detail into what's going on but also contains some really mind-blowing stuff, such as the imaginal disc starting to develop prior to the pupal stage.

3:09 Gonna have to point out cockroaches are NOT holometabolous, they do not pupate and the nymphs look like smaller wingless paler adults

I'm real curious as to how this process originated. It's such a drastically different life stage from what other species do it's hard to imagine how they might be related.

Great video! I was trying to research that exact things a while ago but I couldn't find it in a way that I would understand, now I did!

I have been wondering about this in particular for quite some time, thank you for uploading this.

Fascinating video! Though, cicadas go through INCOMPLETE metamorphosis. I loved collecting their shed skins as a kid! Lol

This is my favorite video of this week 😊 Very cool, everything I saw here. I always wondered about the pupa stage 🤔🙏🏾

I am so glad you recovered!

And here I thought the transformation my wife goes through before we go out was miraculous.

I love the closed captions, especially towards the end

Thanks for this video. Always wondered what was going on in there

Most insects go from larva to the final form, but somehow butterflies have a better PR

yes i know this fact because theres this visual novel game thing titled butterfly soup. its definitely about butterflies and arthropods trust me

Very interesting video! We just became a Monarch Waystation about a year ago. Last fall was our first time rearing , tagging and releasing Monarchs. It was the most amazing process but watching them emerge was probably by favorite. It’s a lot longer process than I thought, they typically stay a good hour or so in the same position just swinging back and forth and pumping their wings. We have only had one bad chrysalis so far so not a bad record!

Woooow!! I wish there was a super like button on RU-vid to smash it right now! I love this video, I had always wanted to see the inside of a chrysalis and thanks to your flawless explanation now I understand metamorphosis way better. Thank you for your work! 🙏

Tldr: the caterpillar turns into a production line, only retaining basic vital organs as the rest of the body turns into liquefied mini-factories, each "factory" tasked with manufacturing a different part - legs, wings, eyes, etc. Then all the parts are assembled together and voilá, butterfly! And somehow, they can RETAIN MEMORIES after this process, remembering information from when they were a caterpillar!

I literally asked myself about this and now I see this upload. I love this channel

The Anti-Hero reference did not go unnoticed.

4:27 SCARY AMBIENT NOISES

In the United States, students are typically taught about butterfly metamorphosis in elementary school, specifically during the early grades. The age at which students are taught this subject can vary by school district and state, but it is commonly covered in early elementary grades, such as kindergarten through third grade.

2:00 - 2:03 "It's me, hi, I'm some people, it's me" sound awfully similar to "It's me, hi, I'm the problem it's me"

I was so excited at the start, it felt like i was about to watch pbs be smart, pbs eons, & just keep thinking in a single episode. Please check the last one too. I hope scientists would discover how holometabolous development evolved soon.

I've always wondered about this. Thank you for making this video

I literally googled this yesterday and got distracted before I could find out the process 😂😂😂 this video is just what I needed

Hi Joe, when I was a kid my granddad found a thumb-sized black caterpillar covered in hairs. He put it in a plant propagator box with a privet twig. Days later, it pupated. Turns out it was a beautiful Privet Hawk Moth, with magenta and lime green wings. It did its first crap on my thumb, and fed it with sugar water on a microscope slide. I never forget it warming up its flight muscles by vibrating. We released it shortly after, and it remains my fave childhood memory.

By far the best and most comprehensive video on metamorphosis I have ever seen! Possibly the best on the internet! ❤️🦋❤ Not to mention entertaining! "Eric Carle didn't mention that part did he!?!" 🤣

I actually feel validated that Joe pronounces the e in winged when just the other day I was corrected for doing just that.

There is so much about our very souls that you may have very well shown us today/tonight, good sir. This was awesomely informative. Thank you!!

It is a very fascinating thing. It has been weirding us out, probably since we began to think about things abstractly. But while the various forms of complete metamorphosis are all very interesting, I have always considered the incomplete metamorphosis to be much more curious. Take the larva of a dragonfly. While not as completely different as a larva is to a butterfly, it is still remarkably different from the adult animal. But one day it simply says "I'll go up that talk and shed my skin and then fly away." As in for a while a fully adult dragonfly was running/swimming around in an insect version of an encounter suit. That has got to be among the most weird things. And yes, I did notice the part about the proto-wings in the larva. And that is probably connected to the dragonfly approach.

Thanks for the video, finally it answered something I wanted to know for sooo long

They taught us in 80s/90s in school that caterpillar turns to bug soup in chrysalis and then reorganizing and forms a butterfly. Can't believe it

I’m obsessed with the way you said “Like a JACKET” 😆😆😆

It's an example of the Swiss Army Knife effect - if you have a tool that can do a bunch of different things, it will do them all but poorly, like a swiss army knife. By confining the eating and growth phase to one body plan, and the mating and reproduction phase to another body plan, each body is optimized to that task. All life forms and functions strive for maximal energy efficiency.

It was very interesting to look inside the cocoon, thank you. I never thought that magic happens there. I was about right in imagining that a caterpillar grows new limbs while it is in a sleep-like state.

Omg!! Joe I haven't seen that caterpillar book in years. Nostalgic

Great episode! Well done 😂

What a wonderfully informative video. Well done. Old uk duffer here :)

I remember this 'parents not competing with children' thing was used to describe T-rexes

Great video!

This is SO COOL! I also thought they went from goo to butterflies. Wonderful!

Complete to incomplete metamorphosis is a spectrum. Different species, different amounts of development per molt. The goo is just an over simplification and there are many pupa that are strongly dominated by goo rather than structures visible to the naked eye. In some butterflies you can see into the matrix as the structures develop. I recommend swallowtails. Cicadas are usually classed as incomplete metamorphosis, not complete, which is to say the structures grow strongly between each molt with less goo so they don't suddenly dramatically change form, you can see this in the casts left on trees which are nearly identical to the adults minus wings and a few other changes.

15:18 is so true especially when the thumbnail is like "Is this yellow banana really yellow" and I'm like 😬

Have you tried joining nebula? It’s a streaming platform like RU-vid but it was made by a bunch of educational youtubers without an algorithm I think you might fit in quite well I really enjoy the channel thanks for the information joe!

Oh my gosh, that’s one of my favorite books - it came out when I was 3, and my grandmother got it right away 😄

I never heard of the goo myth. It was obvious that there was a morphing, a metamorphosis if you will, that happened.

I was shocked when I found out about this during one of my random searching this up sessions. I was even taught about the soup stage!

Love this!! Thank you ❤❤❤

Feel so sad for butterflies that they never are nurtured by their parents, they are just left to "go figure out"

I am just now finding out that he is not hank green but in fact another person. I have been watching for years and never realized.

When I was a child, I wanted to go to university to be the first person to figure out how catapillars become butterflies because it seemed like no one knew.

Ok…. I can’t be the only one ready for Joe to publish a children’s book “The very stinky maggot.”

I'd imagine that this all started to have smaller eggs. So the original ancient bug this adaptation comes from had the larval stage still in egg. But then a mutation caused one to hatch early and eat up the surroundings. So if they break out early and eat stuff outside the egg, the egg doesn't need that "food" and can be smaller. Kind of like human babies. They are born early, and have to be raised outside. This keeps everything small. So instead of laying one big egg that becomes a butterfly, you lay a bunch of tiny ones.

Good timing. I've seen butterflies everyday this month.

I was the teachers choice for "growing" the Monarch Butterflies for 4 years in elementary school and it was my favorite time of year.... We released probably 400 over all the different classes that did it. 😁🦋❤

Why children books doesn’t have these stages explained because i think they still don’t have the age to understand that deeply.

I'm waiting on a postponed and desperately needed surgery that will give me my life back. I have been having a very hard time waiting after 3.5 years of f*ckups and constant letdowns. In addition to my amazing family and friends and my ability to still see the beauty around me (and clearly see the awesome life waiting for me), I keep saying to myself "I am caterpillar soup now, but I will soon be a glorious motherf*cking butterfly" followed by "everything I need to heal is already inside me". I was thinking this when I woke up then 5 minutes later this showed up when I popped onto YT. Hell yeah 😁🖤.

I've heard about the "caterpillar soup" many times, but when watching an actual caterpillar transform, I thought that this definitely does NOT look like a soup, and either some people have a weird definition of "liquify", or something is quite wrong about the "soup" explanation.... my 2 year old is very interested in watching caterpillars metamorphose - now I'll make sure to tell her about the REAL way they do it 😊

I was so unsatisfied as a child with the explanation that they were bug soup. Thank you for this amazing revelation!

Still didn't answer my questions regarding the subject. Like, how does a caterpillar manage to keep eating, moving, breathing etc when a new body is developing underneath its current skin? At some point, there needs to be 100% detatchment between the old and new, right?

I remember this class in school. And they stuck to the “sews a cocoon and crawls in then goopifies then magic, poof”. Makes so much more sense that they just molt again

Fantástico! Amazing! Loved!

My favorite RU-vid channel. Thanks Joe and team. I don’t mean to sound greedy, but it would be awesome to see you more often