When we discovered this caterpillar, he was already over 1 1/2 inches long. We found him on our False Indigo Plant – the caterpillar creates a web around its own personal feeding area. (Villa Park, IL USA)
It took some searching and the help of a friend, but your yellow caterpillar will turn into the Genista Broom Moth (also called the Sophora Worm).
These moths are found in most of N America and Mexico.
The caterpillars feed on Baptisia (false indigo), Lupines, Acacia, TX mountain laurel, and other pea family shrubs. In the south there are several generations. It overwinters usually as a pupa tho sometimes as an adult.