Found this on a wild grapevine today. From another description on this site, I think it might be an Achemon Sphinx caterpillar. It’s certainly the largest caterpillar I’ve ever seen, didn’t have a “horn”, just a dark single spot on rump. The white spots on its sides looked like tiny spirals. It had a very large, flat fronted face. Body was very smooth, with tiny darker dots on it. The grandkids were fascinated, and after studying it and taking pictures, we put it back outside on a grapevine to continue its life cycle. Would love to know what the adult moth looks like. (WI)
Yes! you caterpillar is the Achemon. So cool you found it and shared it with the grandkids!!
You can tell the Achemon from the Pandorus caterpillar because the white spots along the sides of the Achemon are spiral looking as you noted (or figure 8), not solid ovals like the Pandorus. Otherwise these two caterpillars look very similar and eat the same food!
This caterpillar eats leaves of grapes, Virginia creeper, Ampelopsis (porcelain vine), and any related vines.
As a sphinx moth caterpillar, they usually do have a horn on the rear end. Yours is in the last stage of development for this group of sphinx moths, so it has lost the horn and has a spot in it’s place.
This caterpillar will soon be looking for a place to pupate by burrowing into the soil. In the north there is one generation per year(2 generations in the south), so the moth would not emerge until next summer in WI.
This insect is found over most of North America. The moth is really cool looking tho not as striking or colorful as the Pandorus moth.
This caterpillar does not bite, sting, or cause rashes.