A couple of years ago, I've bought a special net to cover the plants with, so no butterflies or anything else could come close. But I never used it. Not only do I like to look at my plants (which I wouldn't be able to do when I put the net over it), but I also completely forget that I have it until I see the first couple of caterpillars. And if they are already there, the net has no use anymore - it's too late already :0)