Woolly Bear - Fuzzy, Fun and Fascinating

I am being invaded by woolly bear caterpillars this year, they seem to know I'll offer them refuge and have been showing up on my back porch, front porch, and all over the parking lot at my apartment! I always see a lot every year, but have never had so many so obviously "on my doorstep"!

The first invader was crawling up my screen door a week ago, and when I went out to put it back in the vegetation, I found three more hiding in various places around my flower pots, so I started putting them all in a bug cage stuffed with crumpled paper.  The news must have spread, because Number 15 was rapidly crawling towards my car as I arrived home from work today.

The first invader - this woolly was crawling up the screen door on my back porch

Woolly bear caterpillars are larvae of the Isabella Tiger Moth, a light orange-brown moth with black speckles that is often seen at porch lights in the summer.  The moths lay eggs in late summer and early autumn, which hatch a few days later.  The larvae feed on numerous plant species, but I usually find them on red alder and various maples here in southwest Washington.  In this area, the larvae always seem to reach maturity before going into hibernation, and then spin cocoons and pupate in the spring, emerging as adults in the summer.  In colder climates, such as northern Canada, larvae have been known to take up to 14 years to fully develop, only eating a little bit during the short summers and then returning to hibernation.  This species has the amazing ability to freeze solid during the winter, and one report I read said that they have been known to survive a winter being completely frozen in an ice cube!  Because of this, they are more susceptible to come out of hibernation early if they are too warm.

The first woolly bears that I found on my porch

I plan to keep these fuzzy critters exposed to cold temperatures on my porch, rather than putting them in my outdoor storage closet, where I usually put overwintering lepidoptera.  I placed a small plastic flower pot in a mesh bug cage, then loosely stuffed the cage with crumpled paper under and around the pot.  The caterpillars seem to like that arrangement, and most of them are either buried near the bottom of the cage or in the flower pot.

Woolly bears, numbers 10 through 13, that I found in the parking lot