Lettered Sphinx Moth

Adult forewing light brown to grayish, crossed by dark parallel bands; outer margin deeply scalloped; a small black-and-white spot near the apex, hindwing reddish-brown with a dark terminal band.
Caterpillar: "yellow-green with sub-dorsal stripe that runs from horn forward over head to antenna. Yellow oblique lines pass under spiracles on A1 - A7... Horn yellow, often with downward curve...early instars more yellow than green with very long black horn that may be yellow at its apex" - Wagner(1) p.271 — Bug Guide.net