The caterpillar was about 2-3″ long and eating the leaves of my butterfly weed. It was green and black with yellow legs and a yellow stripe down its “back”. It had a horn like protrusion at the end. (Chino Hills, CA)
Your photo is a white-lined sphinx moth caterpillar. Caterpillars of this moth do vary greatly in color, but like most sphinx caterpillars they have a ‘horn’ or tail on the rear end.
The moths do look a little like hummingbirds as they fly from flower to flower gathering nectar. The straw like mouthparts are long tubes for sucking up nectar…it is fun to watch them feed. This particular sphinx moth does fly during the day as well as at night.
While the moths do feed on nectar the caterpillars feed on a wide variety of plants like purslane, primrose, and plants in the rose family. We can add butterfly weed 🙂 They are not considered a pest of any crop. They are usually found in open habitats; deserts, meadows, gardens.
This insect is found all over North America, Central America as well as Eurasia and Africa.