It didn't have a horn but sure looked like a hornworm - big green caterpillar with big poop on underside of 1 leaf. And lots of little black "seeds" (poop from other hornworms or smaller cats I didn't see?) on the other plants. I just pick them off my tomatoes but even with no thorns I'm not keen on searching through blackberry plants. What is this and is there an organic control? Sorry, no picture, I squished him.