Upper Size Limits for Insects?

Is there an upper size limit for a creature with an exoskeleton vs an endoskeleton? If so, why?

note: I got thinking about this after recalling the movie “Them” which scared the hell out of me as a young child…

I recently saw a CNN report about an island off the coast of Australia that had some of the largest insects ever found. Apparently they only developed because there were no mammals on the island that could eat them up, as they were essentially huge, crawling hunks of protein.

So apparently other animal life wanting to eat bugs is what restricts their growth in many cases, but I have no idea what the upper limits of an exoskeleton are. I just hope someone will be along soon to tell us, 'cause I wondered the same thing when I heard about “Mimic”.

— G. Raven

Just popped in to say, “Best GQ Topic Ever!” Big thumbs up, xploder! :smiley:

Also, what about all those Jurassic era big bugs, you know, the “dragonflies the size of a German shepherd” sort of thing?

I seem to recall Woody Allen doing battle with a spider the size of a Buick.

I just have to say that I’m adding that first line to my sig :smiley:

I suppose what I’m trying to say is aside from the fact that most insects get eaten prior to attaining a huge size, why are there no HUGE (and I mean REALLY huge) insects? I’d kind of like to have a giant pet dragonfly like DDG describes above.

It IS a great topic and I’m getting anxious for some real answers.

We have some pretty massive fuckers over here in China, but nothing jurassic. Dragonflies are quite big enough thank you, xploder, I could do without seeing them bigger :wink:

When my oldest child was panicked after seeing a part of a movie where insects were huge we calmed him down by explaining that most insects can only get to a moderate size because their body systems could not support a larger frame. A lot of insects don’t really have brains, just sub and super esophageal ganglia (I don’t think I spelled that right). Anyway, their system couldn’t supply oxygen to a large body.

That’s my story, and I’m sticking to it cause it helps me sleep at night.

I don’t see why their body systems couldn’t support a larger frame. Seems to me that with a larger frame, there would be MORE support! As for oxygen supply to their body, huh? Why not? I see no reason there couldn’t be a reasonable supply of oxygen. I know it’s kinda like comparing apples to pinecones but, MICE get enough oxyegn and so do WHALES. The size difference is immense. I also understand that we aren’t talking about lungs here either but spiricules for breathing. I hope I spelled that right. Can someone please enlighten me?

I really want to be able to take my giant pet dragonfly out for a nice fly on his leash…

We actually studied this in either biology or zoology.

The protein that insects and other arthopods use is chitin (kie tin). It’s perfects for small animals, because it’s light and durable. This contributed to most of them developing wings and being able to fly.

Little arthopods (ants, crickets, ladybugs) can fall a great distance without harm because their maximum falling momentum isn’t enough to crack their exoskeletons. But bigger arthopods have a problem falling. Big tarantulas can die from a fall of just 3 feet.

The weight of an animal is proportional to the cube of their size; i.e., a 2" insect weighs 8 times more than a 1" insect. But even if the chitin shell’s thickness is proportional, it’s strength would only increase to the square; i.e., a 2 mm shell is 4 times stronger than a 1 mm shell. So a 10" insect weighs 1000 times more than a 1" insect, but it’s shell is at most 100 times stronger. So the weight soon passes the threshhold of the shells strength.

There’s a similar logic as to why land animals don’t get bigger than elephants. Although stronger than chitin, calcium bones also have a limit to the size of the animal using them.

Aquatic animals can grow much larger because their weight is buoyed.

I asked a question similar to this 05/17/2000 which investigates this same topic.
“Upper size limit for insects?”

It also links to the New Zealand “weta” you refer to.

It’s just that, the spiricles. They don’t have the efficient circulatory system that the other creatures you mentioned have. We, as higher animals, are basically saturated in constantly-recirculated blood.

Damn. And here I thought I had an original topic. Oh well. Thanks for the info and links all :smiley:

Then how does that explain massive dinosaurs?

I obviously watched WAY too many monster movies as a kid…

Hunh? Elephants? You’re not using that creationist biology book again are you AWB?


“The most important bones yet unearthed are two vertebraes. According to Munoz, two cervical vertebraes 3.94 feet high have been found, in addition to a femur some 6.56 feet high and some other indicative bones. The bones, which haven’t been taken to a laboratory for preparation yet, hint at a 105 million year old Cretaceous beast, possibly measuring in at 157-167 feet in length, easy making it the largest dinosaur yet known. The unnamed creature is believed to be approximately 26 feet longer than its closest competitor, the locally found, 100 ton sauropod known as Argentinosaurus.”

I Remember from my college days the answer was that insects can’t get really large because of inefficencies in the distribution of oxygen. This was also give as the reason there are no giant amoebas. Maybe Cecil can get on this because it’s the best question I’ve seen in a while.

RFHIs (Really Freakin’ Huge Insects) are up against two problems: respiration and the square-cube law.

Square-Cube Law: Mass increases as the cube of an increase in size, strength as the square. If you double a creature’s size, you increase its volume (and consequently, its mass) by a factor of eight; its strength, on the other hand, depends on cross-sectional area of it skeletal and muscular structures and only increases by a factor of four. If you scaled a deer to the size of an elephant, its legs would break immediately under its weight–they just don’t scale up. An insect increased to such a huge size would have even worse problems, since we’re talking about a much greater change in size. An insect could not be increased to monster-movie size without its structure changing beyond recognition. Bugs up to the size of a house cat–and possibly somewhat larger–are still feasible under this limitation, but truly gigantic bugs are out.

Respiration: Insects don’t breathe the way mammals do–they get their oxygen through spiracles (tiny little holes in the abdomen), which deliver air directly to the tissues through tracheae (tiny little tubes). They don’t have lungs, nor do they (generally) transport oxygen via a circulatory system. Huge insects would require more oxygen than could be supplied this way. One theory about the ability of the giants of the Paleozoic era to cope with this problem is that they were dependent on the elevated levels of atmospheric oxygen available during that period; their extinction seems to coincide with a general drop in oxygen levels.

So, no giant bugs for you–unless maybe you get them some support hose and an oxygen tent.

Jeez…I ran a search and it didn’t even come up with that! The same title!

Would that mean the Blue Whale would no longer be the largest animal that ever lived?

Great stuff, people. :smiley: Hey, xploder, don’t feel bad–I missed it, too. It turns out that YOUR title is “limits” plural, and Astro’s title is “limit” singular. If you Search with “upper size limits” you get the xploder thread only. If you Search with “upper size limit”, you get both threads. I Searched under “limits” and got only you, hence my “WTG!” So don’t feel bad. Astro, too. Greatest Retroactive GQ Topic Ever!

Anyway, you and astro aren’t the only ones wondering about giant bugs.


Okay, enough chit-chat. Let’s define some terms. Are we talking about, “Why aren’t there insects as big as German shepherds anymore?” or “Why aren’t there insects the size of houses or cars”?

Giant fossil insects.



The giant dragonfly. xnxx ظراط بنات الصين فيديوهات إباحية مجانية على الموقع العربي للبالغين.

Giant spider. *Megarachne servinei *

Giant millipede. *Arthropleura *

I found somebody who says the same thing Balance said, only more fun.

Hee. I love these guys. :smiley: And that’s just the summary–I’m afraid to look at the whole paper.

So, the next question is, “How much atmospheric oxygen would you have to have, in order to have a spider the size of a Buick?”

And Balance, I follow the logic behind the Squared Cube thing, but couldn’t an insect evolve, or change its shape somehow, so as to accomodate the demands of being the size of a Buick? You said, “without its structure changing beyond recognition”, but how much beyond recognition would it have to be? [David Attenborough voice] What IS an insect, anyway? [/David Attenborough voice] Say you had something with short little legs, like a cockroach (Nancyfish, you might want to skip this next part :smiley: ), not long spindly legs like a deer or spider, couldn’t it just evolve short sturdy legs like a stegosaurus, that would hold it up without collapsing? I don’t follow why a stegosaurus could hold itself up and a cockroach couldn’t. And it could just evolve thicker chitin, maybe some internal strutwork, so it wouldn’t collapse under its own weight.

The logical question, of course, would be, “What would it eat?”, and maybe we can let Nancy figure that out for us. Nancy? (I’m cruel, I know it.) :smiley:

Eh, don’t throw away all your “Blue Whale” collector’s cards just yet. Officially, the blue whale is still the world’s record holder and champion.

They found the latest contender for “biggest animal that ever lived” a year ago, in January 2000. The following statement was issued by them in March 2000.

So they’re talking about “longest”, not necessarily “biggest” as in “heaviest”.

The names of the archaeologists associated with it are Carlos Munoz and Sebastian Apesteguia, and their museum is the Florentino Ameghino Museum, if you want to look around on the Web yourself for updates.

I was gonna mention the strength-to-size thing, but that’s taken care of…

Oh yeah, if you can trap a dragonfly (in say, tupperware) and stick in the freezer until it slows down enough to go to ‘sleep’ you can tie it up with some light thread and when it wakes up it’ll be on a leash. I saw some dudes do this to a bee after they watched a skateboarder film CKY2K. Good film, BTW.
punk snot dead

What exactly in my statement made you think I was a creationist?

I hadn’t heard of this new massive creature. And although it may be very long, most of that length is no doubt in the relatively skinny neck and tail. As for pure mass, it probably still is outweight by aquatic creatures.