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!

It could be a hummingbird clearwing moth caterpillar. I used my computer to zoom in on your picture, but still couldn't tell if the spiracles/breathing holes have an orangey ring of color around them. I also couldn't see if yours has a yellow ring around its "face". There are many different types of hornworms, many very similar to each other. Of course, if yours is an early instar/stage, it might not have those characteristics, because it's too young. If I were you, I'd offer it clean viburnum leaves - no spiders on them, please :) - if you have some, and if you don't you could try honeysuckle leaves. I can't tell the size of your caterpillar by the picture, and even if I could, unless I can ID it for sure, I wouldn't know what the likely instar (stage) might be. When your caterpillar has gone through its instars and is through eating, it should spin a "weak cocoon" amongst leaves, according to my best caterpillar book, if it's a hummingbird clearwing. The moth should emerge this year sometime, just when, I don't know. Sorry I can't be more specific, but a closer-up picture would help. Sherry

Thank you Judy--While it seems a little macabre to ask for an ID--it's good to know what it might have possibly been. Also, that the sapling might be a willow. I'll keep a better on it.

I advise against putting it in a jar - I've had fatal results w/ that = ( In the butterfly garden @ the rec center where I work, we just had some sulphur pupae emerge. I tied orange strings to the branches so we could observe them every day w/o disturbing them - also did that w/ a monarch chrysalis. The butterflies will stay on the branch for hours after emerging - it takes a long time for their wings to expand & harden.