the title is pretty self explanatory why can’t bugs be big
In: Biology
Others have noted the oxygen and weight issues. There are also places where things with common ancestors to bugs can survive and grow pretty large, like lobsters. Generally speaking, most things we consider to be bugs are crustaceans. So if you want to find large bugs, a good place to look is in the ocean.
Most of the answers are close but don’t hit it completely.
1. It is possible for bugs to be big, they were big once during the Carboniferous and Permian periods (about 300 mya).
2. When bugs were bigger there was a higher concentration of oxygen, there is less oxygen now a days.
3. The lower oxygen levels wouldn’t be such a problem today but bugs don’t have active gas exchange organs like lungs, they have tracheae or book lungs with spiders and scorpions.
AND the one that everyone is still missing 4. insects have open circulatory systems, along with lungs another ‘inefficiency’ that makes low oxygen levels tough.
Related: Giant scorpions are the stuff of my nightmares.
Bugs lack lungs and hemoglobin. Hemoglobin is what transports/carries oxygen to cells and it’s also why our blood is red (and bug blood is green or clear). Chitin is RIDICULOUSLY heavy and is only useful at a small scale.
They rely on holes in their body to passively respirate (NOT breathe) which limits their size. The larger the bug, the harder it is to have holes that reach the innermost guts.
Every (iirc) multicellular organism requires oxygen to live; the larger and more activethe creature the more oxygen it needs.
In order for a bug to become larger, it must gain the ability to produce hemoglobin (ridiculously hard to adapt), gain an endo skeleton/lose their exoskeleton (arguably impossible), adapt ‘gills’ and a swim bladder which can then be merged into lungs (reliant on hemoglobin already being produced). That, or have the entirety of Earth’s atmosphere become exponentially richer in oxygen, and even then, they couldn’t get very much larger.
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