The hopping clues me in that it's the planthopper mackey77 mentioned. I have had them, they are not very damaging, though they do feed on plant juices. No need to go on a hunting expidition unless you find lots and lots of them (or they are on something really special). Plants can take some feeding damage (it's sort of like our immune system where a little challenge can bring greater overall health). Also, they (hopper larva) are pretty mobile and don't neccessarily sit in the same plant for a long time. I guess overall, not really good guy or bad guy; sort in-between guy... Cheers!

Five-Spotted Hawkmoth (Manduca quinquemaculata) Caterpillar... aka. Tomato Hornworm.....BAD!! Will eat most of the leaves of your tomato plants....simply pick them off and get rid of them.... Ian

Thanks for the input, Erin. I never did figure out what these were--I wish I'd gotten a better picture, or kept the leaf in a jar and watched to learn for myself. I've grown tomatoes for a while now, but this is the first year I've had the time to pay attention to the details and try to figure out what, exactly, is going on in my garden. I've been lucky so far. I started out with loads of aphids and was getting itchy to spray with soap, but instead planted more sweet alyssum among the marigolds around the tomatoes and crossed my fingers. Ladybug, flower fly, and a few lacewing larvae popped up shortly after the aphids did, and the aphid population dropped off. There are plenty of pinkish-tan aphid mummies too, which does my vengeful heart good. So far only a few striped cucumber beetles and no signs of hornworms yet, though I've found a couple gray-brown 1 1/2" long caterpillars near the tomatoes. I'm going to try to stick with the no-insecticide method this year.

My eyes definitely aren't as good as they used to be but I think they may be assassin bugs - a predatory insect that eats other insects both good and bad. Check out the link and see if its the same. Here is a link that might be useful: Assassin Bugs