Large yellow caterpillar found!

A Monarch was laying eggs all over the milkweed again. Found one small caterpillar on a plant that I hadn't seen before. Saw a Tiger Swallowtail nectaring on zinnias in the garden. Saw another Black Swallowtail fly around, she laid some more eggs. Late in the day - I found a great big yellow caterpillar on a senna plant! Might be a cloudless sulfur, I'm not sure. Was eating flower buds, though, not leaves.