Engines of Our Ingenuity

No. 2541

by John H. Lienhard

Today, I relive Charlotte's Web. The University of Houston's College of Engineering presents this series about the machines that make our civilization run, and the people whose ingenuity created them.

Charlotte's Web E. B. White's children's classic, Charlotte's Web, is about a runt-of-the-litter pig, Wilbur, and Charlotte. Charlotte is like a fairy godmother in the form of an Araneus Cavaticus orb weaver, better known as a barn spider. A young girl, Fern, first saves Wilbur from the axe. After that, it's Charlotte who schemes to keep him from becoming bacon, as he matures. And Fern is the lone human bystander who understands the animals laying their plans.

In the past I've talked about spider silk and about orb weavers. Now a barn spider just like Charlotte appeared at our house two weeks ago. That night, she spun a web across our door, closing us in and keeping all evil creatures out. The web was gone at dawn. We could, once more, come and go as we pleased. Every night she's done that same ritual.

Ms. Arachne in her crevice We call her Ms. Arachne, not Charlotte. Ms. Arachne has taken residence in a crevice where a joist holds our roof. Each evening she waits for us to turn off the lights and TV. Then she spins a small hammock next to her hole. From there, she drops to the floor carrying one silk strand -- then climbs back up and repeats, setting the frame of her web. Next, she runs a spiral path, laying down her complex net. It takes about an hour to finish. It's clear we're watching a master weaver. Such craftsmanship! But why is the web gone each morning? Two reasons: One is conservation; spider silk is fine material, not to be wasted.

Ms. Arachne spinning her web

Ms. Arachne eating her web I rose in the small hours one morning to find her in the last stages of eating her web. That's so she can reuse the silk the next night.

I learned the other reason one night when I woke to find Ms. Arachne fastidiously dining. You see, she drinks her meals. Having caught some flying insect, she'd darted out and killed it with a quick sting of poison that would've affected you or me like a bee sting. Then, quick as mercury, she rolled it up in silk taken from the web itself. Now there she was with this big white ice cream cone, sucking everything liquid out of it. She'd left a large hole in the center of the web when she'd taken the silk to wrap her bug.

Ms. Arachne dining She's untroubled by my circling camera. Actually, she can only tell light from dark. Her sense of touch is a lot better than her vision. When I bump the window near her, she reacts by jumping up and down in the web. It's a kind of threatening Maori Haka war dance. We may be friends, but friends understand about boundaries.

E. B. White's Charlotte lasted through Indian summer; then died of old age. Ms. Arachne has been with us for fifteen days as I record this. Unlike Charlotte, she's woven me no messages in her web. Still, she's pretty smart. Her brain is tiny until you include her substantial nervous system. She can learn and adapt. And, of course, like Charlotte, she can teach. She's shown me so much that I never knew. As I study her, night after night, E. B. White's quirky vision of a magical spider seems almost plausible.

I'm John Lienhard at the University of Houston, where we're interested in the way inventive minds work.

(Theme music)

E. B. White, Charlotte's Web. (New York: Harper and Roe, 1952)

Video of a Barn spider weaving a web.
Video of a barn spider capturing and consuming a moth.

For more on spiders and spider silk, see Episodes 1069, 1717, 2435, and 2470. All photos by John Lienhard

Note added, Nov. 7, 2009: We first found Ms. Arachne spinning her web on Sept. 7, 2009. Last night we saw her walking away from her crevice and today she's gone, leaving behind her egg sac, sealed in silk -- just as Charlotte did at the end of E. B. White's story.

Ms. Arachne's last formal portrait

Ms. Arachne: formal portrait

Ms. Arachne spinning

The Engines of Our Ingenuity is Copyright © 1988-2009 by John H. Lienhard.