I would say it looks like Hornworm poo. At first I thought that was a penny beside it, and that would be stretching it "LOL>.

Are you sure you don't have any MISSING plants? "LOL> It sounds like a lot of large scat to have left no evidence of destruction around! You do know that they devour whole sections of plants, even chomping on the tomatoes?

If it's not a Hornworm, perhaps it's from another large caterpillar of the Hawk Moth family and perhaps it is feeding on something other than tomatoes (a nearby privet hedge or an overhanging tree for example) in which case there's no need to do anything. Caterpillars who eat one species of plant are not suddenly going to decide that tomatoes would be more tasty, they stick to the food plant on which they were born.

Linda

Thanks labradors! You made me laugh. No, I don't have any missing plants. I know the signs of hornworm damage on tomato plants, and the plant is fine. With that amount of frass, you're right, entire plants should be missing!

I swept up all of the evidence and separated the plants. I will check tomorrow for any new poo. It has to be hornworms (large ones) but I can't tell what they could be eating!! I googled slug poo b/c I know there are slugs out there. But not a match. And parsley worm poo is green, and the parsley is intact, too. It's driving me crazy.

I don't know what slug poop looks like!

I hope you saved all that poop to fertilize your garden (G).

The caterpillars that feed on Parsley (Queen Anne's Lace, Fennel, Dill, Rue and Carrot) are the lavae of the the beautiful Swallowtail butterfly. They don't get as big as the hornworm. I try to restrict them to one plant, and share because I think they are so beautiful.

Linda