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Woollly Bear Caterpillar – a Weather Man?

Maureen Sexsmith-West ISA Certified Arborist, PR4600A

Folklore says the width of black bands predict winter weather

According to the Farmer’s Almanac, the Woolly Bear Caterpillar is a weather man of sorts. Some believe that the width of the centre stripe of yellow can predict upcoming winter weather.

If the black stripes on each end are longer than the middle strip, the weather will be harsh. A wide centre band is wider we can expect a milder winter.

You can easily spot these banded caterpillars in late summer. I photographed this speedster during a visit to my parents in August. Getting a couple of focused images was a challenge since it was wasting no time moving along the sun room windows.

The larvae put on quite a show in comparison to the dull adults. The Woolly Bear is the caterpillar stage of the Spotted Tussock Moth (Lophocampa maculata). While name would suggest it, this ‘hairy’ caterpillar is not a true tussock (Lymantriidae).

The caterpillars forage until fall on deciduous leaves of the willow and maple tree but can also be found poplar, oak, alder and linden trees.

They might be considered quite anti-social as it tends to be found on its own rather than in groups like tent caterpillars. Because of this, you are unlikely to see any real damage to your trees. So you can enjoy observing them without worry.

They pupate away from their host plants. You can often find their cocoons made from silk and the hairs off their body close the ground. They emerge as adults in the Spring and can be seen from May to July.

Scientists can’t confirm this method for forecasting since there are many variances between the group of ‘woolly bear’ caterpillars.

I suppose, he has as much of a chance of being right as any weatherman. After all, they can only give us their best guess.

Below is the Douglas Fir Tussock Moth found in our region. It is much more destructive – defoliating fir and spruce trees. Eggs hatch to coincide with the new growth in May-June. The damage is most obvious following the appearance of new needles. The pupate in August and emerge as adults in October-November. Since they often reproduce on the same host tree, damage can be substantial in a short period of time. Look for cocoons as a predictor for the next generation. One female can lay up to 200 eggs.

Close up – Gorgeous really.

Moth and Feeding Damage – Lethbridge

Douglas Fir Tussock Cocoon and Eggs – Lethbridge

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