the title is pretty self explanatory why can’t bugs be big
In: Biology
Bugs have weird guts.
The biggest factor is they don’t have lungs and their blood doesn’t carry oxygen like a lot of other animals. Instead, the parts of their body that need oxygen have their own little breathing tubes and absorb what they need from the air. So it’s kind of like they breathe all over their bodies.
That only works if the tissue is relatively tiny. The oxygen can only move so far this way. If their muscles get too big, parts of them won’t be able to get enough oxygen and will die off.
Now, they can be BIGGER. We do know ancient insects could be a lot larger. Like, some ancient dragonflies were as big as small hawks. But we think as more and more birds evolved and started preying on insects, being smaller and more maneuverable helped them survive. So the big ones died out because the smaller ones survived better.
But there’s some size of insect where if they don’t evolve lungs and a different circulatory system, they simply won’t be able to survive. That would be such a radical evolution biologists might not even call the creature “an insect” anymore. They might make a new category and say “this evolved from insects”.
There are also some theories that maybe exoskeletons can’t be strong enough to support larger creatures. This is tougher. We do know that to some extent Physics presented a lot of challenges to massive dinosaurs and one of those big challenges is as the “mass” of the creature gets bigger, the size of the bones needed to support the body gets bigger *faster*. In theory there’s a dinosaur size where the bones needed to support its weight won’t fit inside its body. In practice that doesn’t exist because, well, it’d die very fast if it did.
This is kind of a “What if…” topic though. We can theorize and think about biological exoskeleton materials that MAY support larger insects, and coming up with what the maximum size might be is a fun project.
So the much bigger concern is oxygen delivery. Like I said, for them to get VERY large like horses, they’d need to make so many evolutions we wouldn’t call them “insects” anymore.
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