You do have a Tomato Horn Worm there.
It’s sometimes called a Tobacco worm also, because it eats tobacco plants
but not irises. The adult is not a butterfly. It is a sphinx moth,
a large, yellow, red and gray stripped moth that you may see hovering around
your other flowers in the evening.
tongs of some kind, pull the things off (There are usually more than one.) and
dispose of them.
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