I'm surprised this is your first experience with the Tomato Hornworm. They
are as common as butterflies. They definitely get very large and fat when
they start devouring your tomato plants (stems, leaves and tomatoes). They
have a voracious appetite and will target green or red tomatoes too. They
are very lime green with little white marks on their backs and a red horn on
one end. They tend to cling to the ends of the branches underneath. First
thing in the morning is the best time to find them.

Anyway, they are not poisonous or dangerous; just a nuisance. If you see
some with little white pieces of rice all over their backs, leave them.
These white things are actually the eggs of a parasitic wasp and they are
feeding off from the hornworm and will eventually kill the little devil.
The parasitic wasp is a super beneficial guy to have around in the garden.
I usually pick the egg laiden hornworm off the plant and relocate it
somewhere else. Otherwise, pick off all the hornworms that you can find and
kill them. You can also apply Bt Powder to the plants to kill any younger
hornworms. It is an organic biological insecticide that targets just
caterpillars and chewing larvae. I just had to apply some yesterday because
my tomatoes and peppers were being chewed to death and I couldn't find them
on the plant.

When my kids were in elementary school they would take a jar of hornworms
with tomatoes and stems to school and the kids would get a big kick out of
seeing how much they would eat overnight.

Good luck.

Penny
Zone 7b - North Carolina
"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