C. amyntor can be found from Nova Scotia west to Alberta and western North Dakota and Colorado; south Florida reaching into the Gulf Coast, Georgia, Texas, Louisiana and New Mexico.

C. amyntor adults fly as a single brood in the northern portions of their range from June to July.

Before pupating, the larva shrinks a considerable amount and then sheds its remaining skin that distinguishes it as a caterpillar, revealing its shell-like pupa.

The overall coloring of the imago, or adult, elm sphinx is a gray-brown with wavy markings covering the forewings.

Some specimens have a prominent splash of bright white on their upper head and wings and stand out considerably from other C. amyntor.