Caterpillars are about on soft broad leaves such as tomatoes, herbs, geranium, mint, angels trumpet, Chinese lantern, dahlia and impatiens. They can be hard to see due to their green colour and the fact they reside under the leaf.
Control: 'Dipel' or 'Success' is the best and safest control for caterpillars as its a biological control and doesn't affect anything else. And water plants with a seaweed extract to build up their resistance. Or just pick them off and feed them to the birds.