How do pesticides kill insects?

When I spray pesticide on a roach or whatever, 5 seconds after contact it stops moving and appears to be dead. It appears to be more than just poisonous, it almost instantly kills/paralyzes them. How does the pesticide work so fast, what does it do to the insect? What does the insect feel when sprayed... show more When I spray pesticide on a roach or whatever, 5 seconds after contact it stops moving and appears to be dead. It appears to be more than just poisonous, it almost instantly kills/paralyzes them.

How does the pesticide work so fast, what does it do to the insect? What does the insect feel when sprayed on?

From what I have read the effect it has on insects is similiar to the effect nerve gas (chemical weapons) have on humans, but humans dont instantly die from nerve gas, they die slowly, so why is pesticide so devastating to the insect that it causes almost immediate death?
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