Here comes caterpillar season #phenology

woolybear caterpillar climbing screen

Photo by J. Harrington

We're starting to come into woolybear caterpillar season. I know that because:

1. the photo of the woolybear above was taken on August 24 some years ago; and,
2. the Minnesota Seasons web site says flight season of the Isabella tiger moth (Pyrrharctia isabella) lasts until late July and it takes about two weeks for eggs to hatch, which would bring us to mid-August or sooner

Despite the folk lore about wooly bears foretelling Winter's severity, "the truth is that this caterpillar can't predict what Old Man Winter has in store for us in the upcoming winter."

To be honest, when I think of insects in August, usually it has to do with grasshoppers and trout fishing. But, now I realize August is as much monarch, woolybear, and other caterpillars as it is grasshoppers and beetles falling into streams and rivers.

One of the strange things about woolybear caterpillars is how they Winter-over.

Once settled in, the caterpillars hibernate, creating a natural organic antifreeze called glycerol.  They freeze bit by bit, until everything but the interior of their cells are frozen.  These interior cells are protected by the hemolymph.  Woollybears can - and do - survive to temperatures as low as -90℉. 

So, if you have taken to going for outdoor walks as a way to limit going stir crazy during our COVID-19 pandemic, you can now look for monarch caterpillars munching their way across the undersides of milkweed leaves and, soon, you can watch for woolybears as they search for a dark, comfortable place to spend the Winter. Maybe, by the time we can look for next Summer's Isabella tiger moths, we'll have a better handle on our pandemic and on our government. But then, my mother often used to accuse me of "wishing my life away."

The Caterpillar

Robert Graves - 1895-1985

Under this loop of honeysuckle,
A creeping, coloured caterpillar,
I gnaw the fresh green hawthorn spray,
I nibble it leaf by leaf away.

Down beneath grow dandelions,
Daisies, old-man's-looking-glasses;
Rooks flap croaking across the lane.
I eat and swallow and eat again.

Here come raindrops helter-skelter;
I munch and nibble unregarding:
Hawthorn leaves are juicy and firm.
I'll mind my business: I'm a good worm.

When I'm old, tired, melancholy,
I'll build a leaf-green mausoleum
Close by, here on this lovely spray,
And die and dream the ages away.

Some say worms win resurrection,
With white wings beating flitter-flutter,
But wings or a sound sleep, why should I care?
Either way I'll miss my share.

Under this loop of honeysuckle,
A hungry, hairy caterpillar,
I crawl on my high and swinging seat,
And eat, eat, eat—as one ought to eat.

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