Several beetle larvae carry frass on their backs as a defense against predators. I wonder if your green insect is a variety of the tortoise beetle larva.
Larvae of the folivorous tortoise beetle, Plagiometriona clavata, carry shields formed from feces and exuviae above their bodies.

Here's a clear picture of a

Thanks Anney!
I think that is the pest exactly. And yes evidentally it is both a frass disguise and shield. Although I don't know what they are doing on my Brandywines, as tomatoes are not even mentioned as a possible host plant, the neighbors have plenty of bindweed its preferred host plant, but no these beetles had more refined tastes.
Thanks again for the help Anney!
Ross

Hi, Ross!

For this beetle, tomatoes ARE mentioned as a frequent dining spot for them. There are different varieties that prefer other vegetation. I haven't seen them on mine, but several people posted last year wondering what this strange-looking critter was on their tomatoes. Some of the adult tortoise beetles can change color, like chameleons, but I don't know if the clavate is one of them. All the adult pictures show a brown beetle with apparently some transparency.