Folk wisdom holds that the relative lengths of the bands of the caterpillar foretell the severity of the coming winter
(3). Actually, the variability of the bands depends on many factors. As larvae mature, the reddish bands lengthen
(2). Wetter weather lengthens the black bands
(1). So while not a reliable measure, it makes some sense that onset of an early and thus longer winter will force younger and less red caterpillars into hibernation.