I need something bigger than a cell phone screen to identify sm things, all I can see is a little bitty green worm, too sm. Eggs would have been laid on the underside of leaf. They hid, you seek. Trouble is, you usually don't see the eggs, & then you see the damage before you see the caterpillar. All you can do is start checking the undersides of foliage earlier next year. That's the problem with bugs & diseases, when things are going great, something new & different comes among & takes you by surprise.
& yeah, what Ranger said. You don't want to over look any late lurkers. Insecticides won't do you much good. The moths fly in, lay their eggs & take off. Systemics won't kill the 'pillers untill they eat the plant. Most insecticides won't kill 'pillers by contact, they usually have to ingest their poisons. Hey, chickens love 'em. You could always get a couple 'yard birds'! That's why mom & dad always had the garden by the chicken coop, & they fertilize as they go!
~~~~~~~~PEACE!~~~~~~~~