Do "wooly worms" really predict a cold winter?

[tim314]

I’m not sure if they have a more official name, but I trust you all know what I’m talking about. Those worms with the hair on them. I’ve always been told that you can tell how cold the winter is going to be based on how furry they are. Is this just an old wives tale, or is there some truth to it? And if there is any truth to it, how do the worms know?

[racinchikki]

We always called them “wooly bears,” and we were told that the caterpillar’s weather-predicting abilities lay in interpreting the amount of brown vs the amount of black in its stripes.

According to the National Weather Service:

Even though it is widely believed that the woolly bear caterpillar can predict the upcoming 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. The woolly bear caterpillar’s coloring is based on how long caterpillar has been feeding, its age, and species. The better the growing season is the bigger it will grow. This results in a narrower red-orange bands in its middle. Thus, the width of the banding is an indicator of the current or past season’s growth rather than an indicator of the severity of the upcoming winter. Also, the coloring indicates the age of the woolly bear caterpillar. The caterpillars shed their skins or molt six times before reaching adult size. With each successive molt, their colors change, becoming less black and more reddish. In addition, there are approximately 260 species of tiger moths (the adult of the woolly bear caterpillar) in North America, and each species has slightly different color patterns and hair coverings. As a result, some of the color variations that we see each fall may be just a result of seeing a different species.
As far as the story about the woolly caterpillar’s coat, the caterpillars are just wearing a heavy coat in anticipation of the winter cold. This is how Mother Nature has helped it survive winter. All animals go through this same process in the autumn. Here is something truly remarkable. Once settled in, the caterpillars hibernate, creating a natural organic antifreeze. They freeze bit by bit, until everything but the interior of their cells are frozen. They can - and do - survive to temperatures as low as -90oF. This ability to adapt to cold shows up particularly in the Arctic, where the woolly worms live in a strange state of slow motion. Most caterpillars live for two to four weeks before becoming moths. The Arctic woolly worms, however, spend at least 14 years in the process! The woolly bear caterpillar has even been known to survive an entire winter completely frozen in an ice cube.

The answer is, apparently, no.

[SavageNarce]

@tim314

Do “wooly worms” really predict a cold winter?

Only if they’re working at The Farmer’s Almanac

[AskNott]

The caterpillars you see are the offspring of the ones that survived last winter. So, really, they’re “predicting” the previous winter, not the coming one.

Predicting the past is not a useful talent.

[panache45]

Here in NE Ohio, we actually have a Wooly Bear Festival every fall, complete with marching bands and animals dressed like wooly bears. It’s holsted by the world’s oldest weatherman (I think he used to predict the flooding of the Nile for the Pharaohs).

[tim314]

Regarding the “wooly bear” vs. “wooly worm” thing, my mom, from whom I think I learned the term “wooly worm”, thinks that its a regional expression, probably localized to the south-eastern U.S. I don’t know whether “wooly bear” is used everywhere else or not.

[Gary_T]

For there to be a remote chance of this sort of thing working, there would have to be conditions, months ahead of the winter in question, that both affect the critter’s appearance and relate to several months worth of upcoming weather. Now, I’m not saying humans are smarter than God, but we’re pretty good at figuring out, explaining, and predicting lot of natural and physical stuff. And still, our ability to accurately predict the weather more than three days ahead is marginal, largely because there are so many factors involved and many of those factors are so changeable. The notion that there’s a predictable pattern in there that we’ve missed in spite of all of our study is really not believable.

[Hyperelastic]

@panache45

Here in NE Ohio, we actually have a Wooly Bear Festival every fall, complete with marching bands and animals dressed like wooly bears. It’s holsted by the world’s oldest weatherman (I think he used to predict the flooding of the Nile for the Pharaohs).

Don’t diss the Goddard. He has more meteorological knowledge in his big toe than Willard Scott had in his entire bloated body, even if the wooly bear thing is an old wives’ tale.