# If bugs are to grow large



## Creator (Jul 19, 2006)

Guys I am writing my own version of Mothra something like what the new King Kong would be......

But I have some questions what kind of anatomical changes should be made if Insects are to grow large.

I know the answers lie in the exoskeleton and respiration systems.


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## star.torturer (Jul 19, 2006)

though its not actualy growing large, the Otherland seris by Tad Williams (book 2: River of Blue Fire) has a few chapters on the antics of some evil'y large bugs

anatomicaly they would become very large headed and might collapse under there own weight, they would also sufocate, but as you said you already new this, sory


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## Creator (Jul 19, 2006)

I have theorized an answer
The insects of Mothra's island have advanced air pumps which accelearate the rate of diffusion of air into the cells!

http://evolution.berkeley.edu/evolibrary/article/_0_0/constraint_17

The next headache issues are moulting and weight of exoskeleton


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## Winters_Sorrow (Jul 19, 2006)

Well the problems you talk about regarding exoskeletons and respiration would apply to insects like grasshoppers who rely on spiracles (holes along the thorax) to breathe and secrete carbon dioxide and these lose effectiveness as a breathing method once they reach a certain size.

Mothra is a giant moth though, of the family Lepidoptera so these problems shouldn't apply.
One of the big problems with Mothra is the fact he wasn't nocturnal as most of the moth family are. He seemed to have more in common with the diurnal butterfly family.

Not sure if your revision of the Mothra legend will make him more insectoid which is why you're seeking this information?

Moulting shouldn't be too much of a problem - the problem is what the insects would feed on (they would require a prodigious amount of food), the fact that most insects breed in the hundreds so giant insects would devastate the local ecology and then starve - unless you had giant predators to balance it out but they would need to be numerous as well and every so often a swarm may still occur.


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## Creator (Jul 19, 2006)

My Mothra's stats

Wingspan: 8 metres[teratorn size]
length: 3.5 meter can be negotiated
Weight:[anyone can calculate the wing to weight ratios?]
Reproduction: One or two 1m eggs every year.

Defence: Forearms are sickle shaped for defence against the 
Adaptations: The scales of the butterfly family are a feature that distinguishes the family from other insects. On Mothra the scales are reduced and broaded till it looked and function like feathers on a bird.


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## Creator (Jul 19, 2006)

Winters_Sorrow said:
			
		

> Moulting shouldn't be too much of a problem


 
I beg to differ unfortunately Winter, http://evolution.berkeley.edu/evolibrary/article/_0_0/constraint_05


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## Creator (Jul 19, 2006)

I am thinking of Honeycombing the exoskeleton of the inhabitants of Mandible Island. this will reduce the weight on the insect as it gets larger.

The exoskeleton has two layers outer and inner.

The outer exoskeleton's hardness varies from bug to bug and also whether has it moulted and also varies with body area

The inner exoskeleton remain hard and grows with the animal. When the insect has moulted it ensures the 'hardness' of the bug.


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## chrispenycate (Jul 19, 2006)

Lepidoptera avoid the moulting problem by not getting any bigger after having reached adult status, juvenile forms not having the hard exterior. In general, metamorphosis simplifies the problem (though a fifteen meter caterpillar has it's own difficulties of maintaining structural integrity) Only insects with multiple instars (such as grasshoppers) suffer from that particular vunerability. The big problem with spiracle breathing is not merely gas diffusion, but lack of a carrier to the organs. Big arthropods (lobsters, for example) have a relatively efficient circulatory system, and an oxygen transporter chemical.
One of my best friends is an entomologist, but unfortunately this week he's lecturing in England, so I can't put the question to him (besides, he's a world specialist in bugs, true bugs (hemiptera) and if anyone uses the word "bug" for random creepy-crawlies said person is likely to find portions of his anatomy pinned to a display board, like butterflies; bugs are basic beetle model. with sucking mouthparts instead of mandibles)
Only a minority of moths are nocturnal, actually- and those tend to fly towards light.


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## Creator (Jul 20, 2006)

Err my mothra is of a more realistic size and weight, even the larva is of a more realistic size, the larva is only 5 meters .


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## Paige Turner (Jul 20, 2006)

Not to derail the thread or anything, but does anybody else see an armadillo skull in Creator's avatar?

Sorry, now to get your thread back on topic… ummm… _giant bugs? _ You're mad! MAD, I say!


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## Creator (Jul 20, 2006)

IF that's what you think then I think this place isn't for you. I have seen more fantastic writing here 
Are saying that all of chronicle network people are mad?

And besides everyone has the right to be creative in his or her own way. And about my embryo..... everyone who knew the real me could tell the embryo icon is an embryo right away. the CG film Producer I met earlier in CG overdrive that the icon looks more embryo than a armadillo skull, 
Who gave me that stupid idea?..... someone... and I think it was you....


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## star.torturer (Jul 20, 2006)

good call that embryo, cancles out the evleness of the actual object at hand

life versus death.

i can only see death


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## Creator (Jul 22, 2006)

Lets puts personal biasness aside. My thread is a question for people from the science fiction community to answer and not for spam about my Embryo Icon or armadillo skulls! I have seen one before anyway even though I don't own one!

So keep this thread open for answers....thank you


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## chrispenycate (Jul 30, 2006)

Right, talked to my entomologist, The problemis basically a cube/suare law thing, you double the length, you multiply the surface area by four, but the volume by eight. Oxygen/carbom dioxide transfer occurs at a fluid/air interface within the spiracles; the fluid (blood equivalent, but containing only the oygen contained within it, no haemoglobin equivant" contacts each individual cell.
But the wings of lepidotera are rigidified by fluid turgidity (oh, it's pressure in human) so they already have a pumping system involving the dorsal aorta.
And the wings are enormous relative to the insect.
So, we replace the scales on the moth's wings with feathery structures, through which circulatory fluid is pumped, particulatly by the wing muscles (flight is its greatest enery usage) the thinness of the capillaries adds enough resistance that the wings are still maintained rigid, despite the through flow(don't forget, the wings are even bigger in proportion to the body than with a smaller beast; Square/cube law again, and the legs are short and thick)
The lava is furry, and these spines do some of the same job; but it's a very slow caterpillar: not much energy for anything but eating.
Unless it has several sets of antennae, it'll probably have a seriously curtailed sense of smell (most moths are excellent in this region, but simply scaling them up would spoil this (horribly technical, but I did understand, and can give an explanation if required )


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## Creator (Dec 24, 2006)

Oh I see.... I will be reviving this thread by bumping it up.....

I have been in the Army for a while now.....

So what do you think Nature can come up with if my giant moth or bugs is going to overcome these restrictions. Never mind what happened to the bugs that made them grow to close to veterbrate size.


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## Creator (Dec 31, 2007)

I has been close to a year since this thread was found, and I managed to find some answers to the questions

OK so far insects and other arthropods have 2 constraints that limit their size

1. Exoskeleton becoming weaker as they get bigger and also a molting hazard

2. Their diffusion type breathing restricts their size even further.

Solution to 1: Back up your internal skeleton
I think if insects can find anyway to get their exoskeleton to weight less, their exoskeleton will need an internal structure too like a lotus root or the bone of a bird. I post a photoshop drawing tonight.

Solution to 2: Adopt an avian-type respiration system
The insect should adopt a modified but similar lungs like those of birds. Remember Birds and some dinos have air sacs all over the body. Insects should do that too. And regard for volume changes, the avian lung does not change shape when breathing so will not expand and burst your exoskeleton.

Any comments?


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## Overread (Dec 31, 2007)

hmm; Have you seen "Naussica, The Valley of the Wind" by chance?
there are giant bugs there
I would say option 2 you have devised sounds the best - the lighter exo-skelton makes it sound to a casuale read, weak and feeble; whilst the other description lets you keep the hard outer shell that insects are famed for


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## Creator (Dec 31, 2007)

Yes I have been a fan of mayazaki's works.

Well overread, I was planning that they have an internal and exoskeleton. like the attached pic

Anyone got issues with putting avian-type lungs into a bug?


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## Pyan (Dec 31, 2007)

I would have thought that the weight versus leg thickness problem would be a serious one....look at the size of an elephant's legs relative to its body size, and then scale up from there, taking the inverse-square law into account. A scaled up insect wouldn't look anything like the original model.


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## Creator (Dec 31, 2007)

Of course.... well that's the limit which is... I think a tiger's size for a bug is already enough.


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## Nik (Jan 6, 2008)

*Check out 'Robber' tree crabs...*

Hi, glad you're back okay.

IIRC, those big crabs that climb trees and hack their way into coconuts have gone part way to your system.

IIRC, they've evolved what's almost an 'external lung' under their carapace, vastly extending the scope of their gills. Check out their comparative anatomy. They're a rare example of a transitional species, where you can see the brief intermediate stage...

Um, again IIRC, those ancient metre-span dragonflies thrived at a time when O2 concentration in air may have been higher...

Today, look at how a birds' lung is arranged, such that many species can fly over Everest. They seem to have an efficient counter-current system, rather than mammalian with its stagnant volume...


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## Delvo (Jan 6, 2008)

pyan said:


> I would have thought that the weight versus leg thickness problem would be a serious one....look at the size of an elephant's legs relative to its body size


Also notice how they're oriented (straight and vertical, not lateral or arched) and where they're located (hips and shoulders far apart at the front and back of the body, not right adjacent to each other in the middle as with insect legs). The former is to hold up the animal's weight; the latter gives them room to move without getting in the way of each other.



pyan said:


> A scaled up insect wouldn't look anything like the original model.


I think "history" shows us how big an insect can possibly get and still be like an insect: that's those 3-feet-long, 3-feet-wide dragonflies from hundreds of millions of years ago. Back then, there was no competition from vertebrates, so their only limit was themselves. But lateral/arched legs bunched together in the middle of the body and a protein exoskeleton just weren't meant to hold up much weight and move it around.



pyan said:


> taking the inverse-square law into account.


The inverse quare law describes how things like light and gravity get weaker with distance from the source. I think that what you're thinking of is that volume (cubic) functions such as weight and food/oxygen requirements increase at a cubic rate because volume is in cubic units (like cubic inches), whereas area (square) functions such as structural  strength (based on cross-section size) and cross-membrane diffusion capacity only increase at a square rate because area is in square units (like square inches), so increasing an object's size without altering its shape increases the ratio of its volume-based traits to its area-based traits. If that's what you're talking about, I don't know of a formal name for the concept, but "geometric scaling effect" seems to describe it well enough.


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## Pyan (Jan 6, 2008)

Delvo said:


> I think that what you're thinking of is that volume (cubic) functions such as weight and food/oxygen requirements increase at a cubic rate because volume is in cubic units (like cubic inches), whereas area (square) functions such as structural  strength (based on cross-section size) and cross-membrane diffusion capacity only increase at a square rate because area is in square units (like square inches), so increasing an object's size without altering its shape increases the ratio of its volume-based traits to its area-based traits. If that's what you're talking about, I don't know of a formal name for the concept, but "geometric scaling effect" seems to describe it well enough.


That's what I meant...mixed it up with the I-S law somewhere. (It's an awfully long time since my old physics lessons with Mr "Pink" Floyd.....)
Thanks for clarifying it, Delvo!


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## The Ace (Jan 6, 2008)

For large size, spiracles are out, but you could, theoretically, use book lungs found in other arthropods.  The trick would be to keep the 'Leaves,' the same thickness but increase both area and number, this is how Freda works, although she has the four lungs of a tarantula rather than the two backed up by spiracles that most modern spiders have.

   The problem with the chitinous exoskeleton is more problematic, but if other matireals could be integrated, (as in crabs who have calcium carbonate strengthening their exoskeletons) this problem could be alleviated.

   With Freda, I merely turned the chitin from a two-dimensional layered structure to a three-dimensional matrix.  How feasible this is, I have absolutely no idea.


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