How could a Big Creepy Crawly function?

Giant bugs are a stable in fiction but we know from scientific fact that any such creature would suffocate or collapse under the weight of it's own exoskeleton, but how could a giant arthropod survive in earth-like conditions?

Define "giant". In ancient times, there were centipedes the size of a human.

Around the sizes vertebrates can reach.

That is still overly vague. Vertebrates can be from the tiniest of shrew up to long-extinct giant dinosaurs.

You need to give a more tangible and comparable size range.

If we go by biological history DeMarquis has the rough answer.

Giant insects were in part limited by the amount of oxygen content they could freely absorb from their environment. The largest example on land today are coconut crabs which are roughly comparable in size to some of the largest "giant bugs" from the fossil record.

Edited by TuefelHundenIV on Nov 9th 2018 at 6:32:09 AM

Lets go with sizes comparable to modern day animals but not around dinosaur sized.

Well, the short answer is that you need an atmosphere rich in oxygen and/or devoid of birds (which outcompeted the large insects as predators). See here.

No, i'm asking how they would be able to survive in an environment with similar gravity and oxygen to modern earth, like on an alien planet or a post-apocalyptic setting.

You could always just make the creatures insect-like rather than literal insects.

I gave my own alien bug people both endoskeletons and proper lungs, for example.

Kaisor: Again still too vague. Modern animals range from Shrews to Blue Whales. You really need to be specific. De Marquis gave you an accurate answer. That is what it takes.

Kill off all higher predators (or prevent them from evolving) and evolve a plant that puts out more oxygen.

Some sort of radioactive disaster could give you that.

Edited by DeMarquis on Nov 10th 2018 at 1:24:15 PM

What I do in my own stories is simply say "there's more oxygen on this planet than on modern Earth". Arthropods have a different breathing mechanism which doesn't scale very well, which means that they need to be small in order to breathe...unless there's a lot of oxygen in the atmosphere.

In real life, there /have/ been giant arthropods, my favorite of which being the Eurypterid, underwater scorpions that could be up to 2.5 meters long.

You might wish to combine this with low gravity, too.

Make them primarily aquatic? The buoyancy of water helps support larger body structures, as seen in giant squids and whales. And certain species of crab can grow to an appreciably large size.

Either that or change their internal body structure so that they can actually support the weight. The reason giant arthropods aren't a thing is because their bodies are hard outer shell and squishy insides, and circulation of oxygen and nutrients doesn't have any sort of dedicated system. Get too large and the squishy insides get crushed under their own weight inside the shell and the nutrients can't propagate. So give some sort of internal lattice or support structure to hold up the squishy bits, and actual organ and circulation systems to facilitate nutrient transportation.

Would a closed circulatory system and more advanced respiratory system even be viable with how an arthropod's musculature is structured?

Basically to make a giant arthropod, you'd have to almost completely throw out the actual species classification and just settle for making a creature that looks like a bug but is completely different on the inside.