If the alien insects did not procreate within a set time, they would die due to the changes to their bodies.
This situation was very easy to explain.
Due to the massive numbers of alien insects, they had to have strong procreative abilities.
In the alien insect world, many alien insects consumed weaker alien insects. Thus, there had to be many new alien insects to make up for the loss.
The alien insects that could not procreate were useless to their ecosystem. Natural selection had already incorporated a mechanism to eliminate such existences.
There were some water-world dimensional lifeforms that did not procreate for long periods of time. But each time they did, they would produce hundreds of thousands of eggs.
There was no need for all the eggs to survive. It would be lucky if 1/1000 of them survived.
Demons were the only known dimensional lifeform whose method of procreation was still unknown.
