Look like monarch butterfly caterpillars. If they are, yes they are
poisonous. As to how they arrived, did you plant from seed or buy the
plants at a nursery? If bought the eggs were probably on the plants. I
know birds will leave them alone, don't know about any other predators
though.

If you put them in a jar with some branches and feed them you'll have some
of the most beautiful chrysallis's when they get ready to go through
metamorphosis.

Also, I think monarchs are on the endangered list but I'm not absolutely
sure

Shell


"Stephen Younge" wrote in message
news:mHe3b.217301$Oz4.57751@rwcrnsc54...
Yesterday I saw something that I have never seen before in my life. Huge,
green caterpillars on my tomato plants! I never thought I'd spot the
biggest
bugs of my life in Colorado!

My attention was first drawn to the plants when I noticed tiny droppings
around the base of the containers (20" pots). Some areas of the plants
looked like the leaves and stems had been nibbled. I finally noticed
several, huge green caterpillars clinging to the stems. They were so well
camouflaged that I have to be about 6" away to notice them.

Here are some close-ups of the buggers:
http://home.attbi.com/~stephen.and.kim/1.jpg
http://home.attbi.com/~stephen.and.kim/2.jpg
http://home.attbi.com/~stephen.and.kim/3.jpg

Anyway, my questions a

1. What are these things? Where did they come from? I planted the tomatoes
in pots with store-bought potting mix. Did they arrive by air?

2. I pried 7 of the buggers off my plants, but couldn't find any more.
What
can I do to to prevent them from coming back?

3. Are they poisonous, given that they are eating poisonous tomato plants?
Will birds or other predators go after them?

Cheers,
Stephen
Boulder, CO