How does bug spray work?

I can get a tin of spray and direct it at a cloud of fruit flies and have them spiral downwards until they are little writhing smudges on the ground. Or, if I hit a cockroach it squirms around doing spastic conniptions and expires a few minutes later.
OTOH, there are some combinations of bug spray and bug that take a while to work. There are times when I think that hairspray might be better at bringing down a house-fly. At least the little buggers will stop irritating me if their wings are stuck together. And I don’t care if it takes them a while to die.

I am left to wonder, what is the mechanism by which insecticides do their business? Am I right in guessing that it is some kind of direct attack on the nervous system and that their neurotransmitters no longer function? If that is the case, (apart from the fact that my skin is not that porous), why is it that bug spray has so little effect on me. Is it a case of my nervous system being so different that I am not subject to the same neurotoxins?

I fear that in my rambling speculation I have answered my own question. But I may be waaay off. In any case I would love to know specifics. Fight my ignorance.

anti-cholinisterases. They block the action of cholinesterases…
The insect’s nerves then clog with choline, due to the lack of function of the insects cholinesterases…
Basically its a nerve agent , and they asphyxiate because the nerve agent gets into their air ways first and they then lose the ability to breath

Don’t worry, mammals have a suitable anti-anti-cholinisterase , due to the presence of anti-cholinisterase in the wild (such as common weeds.)

If you read the side of the can, it will tell you what the active ingredients are. Once you find the names of the active ingredients, you can look them up online to see how they work.

One I’ve seen before is permethrin, which seems to reduce yellowjacket wasps to writhing (and then inanimate) lumps of tissue in a matter of seconds after a direct hit.

According to the Wikipedia article, permethrin has oddly specific toxicities. Insects? Toxic. Dogs? not toxic. Cats? Toxic. People? Not particularly toxic (you can buy permethrin shampoo for treating head lice). Fish? Extremely toxic.

To echo the earlier comments, the insects’ actions after being sprayed are very similar to how nerve agent symptoms in humans are described in miltary training classes.

High school biology – I was taught that in part, bug sprays work because insects respirate through pores all over their body, not just through their nose. Suspended particles in the spray clog up the breathing holes, suffocating the little buggers.

Today, that sounds suspect, but I’ve never researched it further to see if that is true. It might have been a typical “teacher lie” to stress the entomological fact of respiratory mechanics.

(Yes, I know there is no such word as ‘respirate’, but it is more likely to be understood by the masses than ‘respire’. It’s like ‘orientate’)

We had no trouble with ‘onanism’

It is true that insects respire through “pores all over their body”, called spiracles.

I can’t rule out the existence of an insecticide that works by clogging spiracles, but I’ve certainly never heard of one.

The Raid Wasp & Hornet Killer I mentioned earlier does not. It uses cypermethrin and prallethrin, both of which are pyrethroid neurotoxins. They work by interfering with nerve signal transmission, not by clogging pores.

I am no expert in any relevant subject, but I have trouble imagining an effective insecticide that worked by that mechanism. Wouldn’t you need a very dense cloud of the stuff to have any hope of clogging a large percentage of the spiracles? You might be able to do it to one bug at a time with a narrow spray, but I’m dubious of clearing a room of multiple insects by that method.

In one way or another, they all affect insect’s nervous systems. Some (organophosphates, carbamates) inhibit cholinesterase, which leaves insect (and human!) neurons in an excited state. Others (organochlorines) open sodium channels and cause the neurons to fire randomly. Others inhibit the closing of the sodium channels and cause the same basic effect (pyrethroids). Others competitively populate the acetylcholine receptors (neonicotinoids) and produce something similar to the organophosphates.