Some insects grew to 1M (or more) in length due to the high oxygen content in the past (talking about millions of years ago btw!). 
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Small presence of cockroaches, ants or rats in the cities is nothing more than a beautiful aprovement of our still health living environment.
I repeat: small number of them
Missing of them means something is wrong in our habits or things that we use everyday.
If the such things that we use kills them than what about us?
p.s. they also have the right to live, maybe they don’t pay the rent and other taxes for using the comfort of “our teritory” but that is a key: they live in a much more organised societies because they do not need money 
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