I bet that its actually grasshoppers eating your basil. We had a major infestation a few years ago. There are several ways to go, some slow, some fast, some extremely toxic and some more gentle. The slow gentle way is with stuff called Nolo bait, it is a biological insecticide which will only affect the grasshopper, not the birds or cats or whatever else may eat the insect. Diatomatious Earth is also non toxic, but dont breath too much, and probably faster than Nolo. It is made from crushed teeny tiny ancient sea creatures which tear up the insides of hard shelled insects when eaten. Turkeys are my favorite solution, they dont scratch and eat voraciously. Also, if you can create a cool and wet environment, not so much what basil adores, the grasshoppers can not metabolize and slow down their eating tremendously. Of course there are hardcore, toxic chemicals that one can choose, but they are awful for the entire food chain including the soil which is the base of nutrition for all beings