Source: Pohl, GR, Patterson, B, and Pelham JP. 2016 [unpublished]. Annotated taxonomic checklist of the Lepidoptera of North America, North of Mexico. EXCEL version 1.1. (15 June 2016)
[Pyrrharctia californica Packard 1864]
The Isabella Tiger Moth can be found in many cold regions, including the Arctic. The banded Woolly Bear larva emerges from the egg in the fall and overwinters in its caterpillar form, when it literally freezes solid. It survives being frozen by producing a cryoprotectant in its tissues. In the spring it thaws out and emerges to pupate. Once it emerges from its pupa as a moth it has only days to find a mate.
In most temperate climates, caterpillars become moths within months of hatching, but in the Arctic the summer period for vegetative growth – and hence feeding – is so short that the Woolly Bear must feed for several summers, freezing again each winter before finally pupating. Some are known to live through as many as 14 winters.