It is a yellow hairless caterpillar with white and black spots. It was found on a Sun Dew plant in a small bog, but it seemed lost : ) (Alfred, New York)
It is a Chain-dotted geometer moth caterpillar.
This is one of the ‘inch worms’.
It is found in bogs, barrens, heathlands, and woodlands from southern Canada to MD, OH, and KS. It is known to be found in healthy bogs. You are correct that the populations do ebb and flow. Tho generally they are waning in New England.
There is one generation per year.
This insect overwinters as an egg with larvae emerging in June then pupating in August for about a month before the moth lays eggs for the winter.
Larvae feed on a variety of trees and shrubs including alder, bayberry, birch, blueberry, bog laurel, cranberry, fir, huckleberry, leatherleaf, maple, oak, pine, poplar, sweetfern, sweet gale, tamarack, white cedar, and willow.
Larvae hang straight down from a twig during the day then feed in evening and night.