I believe the rate of their reproduction in a habitat without known predators will allow them to multiply extremely fast and thus change the atmosphere quickly.

Let me fill you in on a little secret. A lot of people don’t know about this secret, but you are about to learn it.
NASA doesn’t want us to bring anything to Mars. No seeds, no germs, no nothing.
Unfortunately, we already have brought microbes with us and now there’s danger of cross contamination. We do not want to contaminate Mars. We want to keep it pristine so we can study it.
No one is going to bring insects there on purpose.