I’m always shocked by how little we know about spiders, including this shocking new discovery that the common garden center spider creates super-strong webs out of super-thin silk strands by shocking them with an electrostatic charge.
The current edition of Biology Letters spins the story of researchers Katrin Kronenberger and Fritz Vollrath of Oxford University’s Department of Zoology and their quest to find out how the Uloborus plumipes (garden center spider or feather-legged lace weaver) creates nano-scale fibers far thinner and stronger than the micrometers-thick silks of most other spiders. They also wanted to know why its web is dry and fluffy.
According to Dr. Kronenberger, they took micro-videos of adult females spinning and studied their cribellum, an unusual and rare spinning organ that creates dry silk rather than the more common wet, sticky filament.
Uloborus has unique cribellar glands, amongst the smallest silk glands of any spider, and it’s these that yield the ultra-fine ‘catching wool’ of its prey capture thread. The raw material, silk dope, is funneled through exceptionally narrow and long ducts into tiny spinning nozzles or spigots. Importantly, the silk seems to form only just before it emerges at the uniquely-shaped spigots of this spider.
How does the web get fluffy? Professor Vollrath says the spider’s hind legs have hairs that the emerging silk brushes against, picking up an electrostatic charge in the process.
This combing and hackling — violently pulling the thread — charges the fibres and the electrostatic interaction of this combination spinning process leads to regularly spaced, wool-like ‘puffs’ covering the capture threads. The extreme thinness of each filament, in addition to the charges applied during spinning, provides Van der Waals adhesion. And this makes these puffs immensely sticky.
That “Van der Waals adhesion” is the same force that makes clothes stick together in a dryer until folding time. In this case, it makes insects stick to the web until feeding time. If the polymer industry could recreate this technique, it would make longer and stronger fibers possible.
Now put down that rolled-up magazine and let the spider teach you something else.