Monday, November 23, 2009

Woolly Bear Caterpillar Predicting the Weather in My World


Woolly Bear Caterpillar - Pyrrharctia isabella
(Photo:  Jo Smith on 11/14/09)


Folklore says: The longer the black ends on a Woolly Bear caterpillar, the longer and more severe the winter will be.

Entomologists say: The amount of black varies with the age of the caterpillar and the moisture levels in the area where it developed. Also, the length of the black ends can vary on caterpillars grown out together from the same group of eggs.

BugGuide makes a half-hearted defense of the Woolly Bear's powers of weather prediction by saying: The variability of the bands depends on many factors. As larvae mature, the reddish bands lengthen. Wetter weather lengthens the black bands. So while not a reliable measure, it makes some sense that onset of an early and thus longer winter will force younger and less red caterpillars into hibernation.

Woolly Bear caterpillars are the larval stage of Isabella Tiger Moths (Pyrrharctia isabella). They are common throughout almost all of North America. Larvae eat many plants and trees including grasses, asters, birches, clover, corn, elms, maples and sunflowers. There are usually two broods of P. isabella each summer. The first of two broods pupates in summer. The second brood overwinters as a caterpillar and pupates in spring. A photo of an adult Isabella Tiger Moth is here.






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26 comments:

John said...

I think I'll trust the entomologists rather than the folklore. BugGuide makes an interesting case for the Woolly Bears as weather indicators, but their case seems more like hindsight than prediction. If it's so cold that younger caterpillars are disappearing early, you already know that winter is starting early.

Great photo, by the way!

Lisa at Greenbow said...

That tiger moth isn't as pretty as its caterpillar. I must have driven through a mass hatching of the caterpillars a couple of weeks ago. I had never seen so many on a road before. I wonder what masses of them mean?? I have seen several big groups of them lately.

Marvin said...

Thanks, John. I agree. Some folklore is crudely based on facts, but the case of the Woolly Bear looks like a clear win for science.

Martha Z said...

Great photo of the Woolly Bear and very intersing. I always totally dismissed the folklore, its interesting that there is a hint of reason in it.

Stephany said...

Great macro and an interesting post. While I lean toward the scientific data, there's always some truth to folklore.

Riet said...

What a lovely pictures and I love your story.

Tom said...

I agree with John's assessment of Jo's photo. Great capture. I've never noticed how tufted the "hairs" of these guys really are. Very cool.

Tom

jeannette stgermain said...

Great photo! thanks for sharing:)

Sylvia K said...

Terrific photos of the Woolly Bear! And very interesting folklore, but think I'll stick with science this time!

Have a great week!

Sylvia

Snap said...

So, what do you think the weather will be like?!!!!
Lovely shot! Interesting post.

Marvin said...

Lisa: I have no idea what large groups of Woolly bears might mean, other than it's been a very good year for Isabella Tiger Moths in your neck of the woods. The Michigan Entomological Society says these cats are normally solitary.

J Bar said...

Spooky.
Sydney - City and Suburbs

SAPhotographs (Joan) said...

What a cutie Marvin. Any truth to the belief on the length of the hair? :)

Jay said...

Interesting info on the Woolly Bear's weather prediction abilities - or lack of abilities! Love the picture .. now, which end is which? LOL!

birdy said...

Though I don't believe on folklore, but still like to read and hear them. Interesting post.

Kaytabug said...

WOW! What an amazing close up of the Wooly Bear!! I really enjoyed reading more about the lil' caterpillar!

Gwendolyn said...

This is a great picture of the woolly bear. Great details. I had heard that they can predict the length of winter. Thanks for sharing your research with us.

lisaschaos said...

Folklore's more fun than science but I'm sure the bug guys are more right. :O)

Wren said...

Whether he's right about the weather or not, he's cute as a bug.

AphotoAday said...

Seems like it's been way too long since I've stopped to watch one of these little fellows... --The coloration on yours is really pretty -- I've forgotten what ours look like around here but I think they have some yellow bristles... I'll have to go looking...

laughingwolf said...

coolios... i've seen them on occasion, but not here in nova scotia

tess said...

It was such a joy to find these when I was a child. I think they were more endearing because we called them Woolly Bears. When I mentioned them to a younger person -- a young adult person --, they had never heard of them. I hope they are not becoming scarce in New England. I found two recently but they weren't alive as they were on a path where there was much foot traffic.

Q said...

Before entomologists we only had wives telling tales and the farmers making predictions....
I do like folk ways. I hope we never forget them. I still lay in firewood regardless of what the Wollies say, climate change and all....
Hope the winter is mild for you.
Sherry

Pat - Arkansas said...

Jo's excellent photo reminds me somewhat of a heavy duty shoe/boot cleaner.:)

From what I hear and don't believe from TV weathercasters, I'd just as soon trust a Woolly Bear.

Speaking of wives' tales: Are there spoons (shovels)or forks in the persimmons this year?

Rambling Woods said...

I haven't seen any woolly bears in person although it seems that they should be around here in western NY. Michelle

PixelShots said...

hi,
happy that i haven't missed your blog.. seems am talking to a professional photographer here.. loves to know about the cameras you using and i would like to know which type and brand of camera felt better to you from your experience..