system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: how does bug spray kill bugs?

So when the pest exterminator comes to treat my house on a quarterly basis, he sprays this liquid sparingly on the outside parameter of my home. Sometimes (not often) I will find a roach inside my house BUT IT’S ALWAYS DEAD! How does the pest spray work? The pest spray can’t be wet when they walk through it because I find them weeks later.
gpt
It depends on the specific chemical, but a lot of them are some form of insect-specific nerve agent. There are a variety of modes of action, but the most common (afaik) is inhibition of acetylcholinesterase, preventing nerve signals from turning off. This is the same mechanism of action as sarin gas, but the chemicals used will only (intentionally) affect insects.