Some caterpillars are feeding intensely in preparation for their winter sleep. After feeding alone during the summer, the animals spin cocoons up to a half-inch down in the leaf litter, where they metamorphose into adult moths.
Eggs hatch out as leaf-eating caterpillars, completing the life cycle.
Occasionally populations can build up to outbreak conditions and really 'hammer' fireweed for a season or two,'' Holsten said in an e-mail message.