I lucked out when I took this photo of an orb web; the individual strands of silk illuminated by the early morning sunlight. Normally an orb web is practically invisible. That’s why they are such effective traps.
But there’s one group of orb weavers—the writing spiders—that decorate their creations with highly visible patterns. These conspicuous silk structures are called “stabilimenta” or singular: stabilimentum, a great word to drop into any casual conversation.
Why go to so much trouble making a normally invisible web visible?
Theories vary. And the weavers themselves are mute on the topic. Writing spiders like the ones in the genus Argiope tend to be brightly colored and they often position themselves in the center of the web. The stabilimenta may help camouflage the orb-weaver or make them look larger. The patterns also reflect UV light, which may serve as a lure to possible prey. Plus, the pattern may help keep birds from flying through the web, tearing it down.