The insects of the plant are people-sized, highly intelligent, with a diverse urban culture that brings many species of ant, and inquiline together. Our narrator is a human exchange professor at one of the finest ant universities in the biggest city on the planet.
Of course, insects on earth have rarely grown to be such sizes. From what I understand there are two main constraints:
- Exoskeletons present difficulties at larger scales.
- Insects do not generally have active lungs, so getting O2 to all parts of the body presents problems as surface area decreases relative to mass in larger bodies.
The ants on the planet of the ants are very similar to earth ants, but this is convergent evolution at an extreme-- distant paths to a similar pattern rather than a familial relation. The exoskeletons of the ants are simply much stronger than the chitin of earth insects, due to a mutation that unleashed huge insects on their planet long ago-- and resulting in a very different evolutionary history. I would love to have some sources or speculation about just how the chemistry and structure of chitin might be altered to make this possible--
Also, these insects have something like lungs.
Are there other biological considerations for huge insects? Could there be constraints on vertebrates on this planet that don't exist on earth? (A reason why all of the animals with backbones are tiny... maybe there's no calcium except deep in the ocean? I really need to learn more about how mineral composition interacts with biology.)
I've considered a lower gravity... but, don't like this much as it over-complicates human visitors. Their planet is like ours but on their planet the insects came out on top.