Exoskeleton strength: A solution?
So is there any solution to this problem? Is it possible to evolve a stronger exoskeleton or stronger "tubes?" Well, wider tubes are stronger than narrower ones. Perhaps if we gave our giant ant extra-wide legs with an extra-thick exoskeleton, it wouldn't suffer so many broken limbs. Does this ant look like it might be a winner? Click the button below to find out the fate of our elephantine ant.
Extra large means extra heavy
Nope, it turns out that evolution can't scale up ants indefinitely just by making their legs extra-wide. The problem is one of weight. An extra-wide exoskeleton must be extra heavy, and that clunky armor would require extra strength to move it. But unfortunately for our ambitious ant, its muscles can't get stronger at a pace that competes with the extra weight the exoskeleton adds. A large terrestrial arthropod with extra-wide legs and a crumple-proof exoskeleton just wouldn't have the muscle power to move itself around!
Evolution and the exoskeleton
So the physics of the exoskeleton could have limited the evolution of larger-bodied arthropods. Even if it were advantageous for an ant to have a larger body size, that ant would have other disadvantages that offset the benefits of increased size: legs that couldn't support its body or an exoskeleton so heavy that it couldn't be moved around. Extra-large is not extra-good for terrestrial arthropods.