How your mix works is the alcohol in the listerine kills them, along with the detergent which allows the alcohol/water mix to coat the insects. There are special insecticidal soaps to spray insects with, that just coats and smothers them. There are also other ingredients in listerine that are insecticides.......and add Listerine mouth wash and Soap..It's a great mix and works magic..
listerine ingredients
Your mix has the soap and ethyl alcohol, which enters the insects breathing apparatus efficiently and kills them faster. When you spray insects with soapy water, they can't fly well as the soap allows the water to coat them. If you spray with just water, it just pisses them off, and they can still fly. Drop an ant in a cup of water, it will float and swim around. Add a drop of detergent, and it sinks. Insects shells repel water well.
The permethrin concentrate I mentioned, has an emulsifier (think soap) that allows the permethrin, which is hydrophobic, to mix with the water.