Came home yesterday evening and there were a few dozen on the potatoes. I found yesterday that spraying with alcohol kills almost instantly. I don't think it damages the leaves because it evaporates in just a few seconds. Hope I'm right. They're very tricky. If you reach for them to hand pick, or they see your shadow over them, they simply go limp and fall down into the foliage where you just can't find them.
Once in awhile, a really big black version of BB comes, and they especially like tomato leaves. If you think a hornworm does fast work, it doesn't compare to the big black blister beetles. (bbbb's)

Both kinds in hordes can strip plants in a few hours.