Not a particularly exciting bug but I thought it looked good against the orange of the Cosmos. I've checked it several times and it doesn't appear to be eating voraciously, just kind of hanging out on the flower. So I let it stay there ;-)
As an aside, a dear friend gave me some of these Cosmos seeds about a year before she died of breast cancer. I finally planted some a couple of years later and they grew happily, so now I collect seeds every fall for next spring's crop and thoroughly enjoy these beautiful and cheerful living reminders of my friend and our shared love of gardening.
Yes, I like the orange BG for the green caterpillar. A lovely tribute to your friend. I wonder if it isn't drinking the water drops? (Yes, I was quoting you on 'fleshy,' but to tell the truth I agree with you.)