Little green worm isn't much help, but here's some info Here is a link that might be useful: Cuke pests

Perhaps the caterpillar?

The seedlings are anywere from 2 days to 2 weeks in the ground, making them 8-10 weeks old. Some of the plants were very frail and others were pretty tough. As we've gone along, the plant killer has moved higher on the the stems. My most recent attempt, which was right before the mouse theory here, was to put a small cone of plastic rabbit fence around each plant. It created about a six inch diameter circle around the 11 remaining seedlings. I figured that if it is a small rabbit, I would either keep it out or at least be able to see the way the animal got around the barrier. I'm down to 9 plants now. two more have been cut off right above the 8 inches of vinyl tubing that I put on the protect the stems. There was no visible disturbance of the cone. It's like it either came down from the sky or up from the ground. I planted the remaining five seedlings in large pots and put them by my front porch. At least they'll get me a few nice tomatoes this season, but it looks like I won't be needing my canning supplies in August. As for next year, I'm going to start working on a plan for some sort of wire mesh cones that will be burried in the ground around the plants. If it is a mouse, it is more than likely that this particular one will be dead by this time next year, and that others won't share it's desire to kill my tomato seedlings. However, I'll be prepared just in case.

Thanks for the feedback! I decided I didn't want to mess with them anymore so late in the season, so I just took off all my green tomatoes and brought them inside. Now I'm researching ways to ripen green tomatoes (I'm seeing newspaper is a popular method). But I will try the Sevin next year if I have the same problem. I'm going to try a non-heirloom variety next year to see if I have better luck. I did try taking a picture, but my camera is acting up and would not behave. I'm pretty sure it was the beetles. They would burrow their way inside and just eat themselves silly. Thanks!