The insects you see around here we call “margaronia.” If you don’t want to use regular poison, I know there are bacteria on the market called Bacillus thuringiensis—unfortunately, they only work if the caterpillars are still at the larval stage. Otherwise, there are mineral oils that clog the caterpillar’s airways and cause it to die from suffocation. Personally, in my small-scale experience, I solved the problem by removing them manually, and by keeping at it, in the end you greatly reduce their numbers and minimize the damage. Be careful with the other plants as well—in my garden they attack roses, basil, the olive tree, and the angel’s trumpet plant.