It’s something that some orb spiders do, a web embellishment whose purpose is debated. It’s called a stabilimentum, and arty spiders named Shea or Absinthe (Charlotte is just too on the nose) spin it out aciniform silk — different material than they use for the surrounding web. Typically its done in concentric circles or an “X marks the spot” dead center.
My spider had a unique vision, a man in a hat, clearly, and after I discovered and oooed and ahhhed over the thing, she must have felt obliged to make progress, so she tackled the neck (not her best work) and that second leg, trailing off to answer her phone, perhaps. (Here’s a funny thing about spiders building webs while on drugs.)
Do stabilimenta keep birds from crashing through? Make the spider look bigger and scarier to predators? Attract potential mates or prey? Create stability–a sort of rebar for webs?
Or might some spiders be designers at heart who can’t help but do a little extra zig and zag? I can imagine this spider finishing up her orb, stepping back to admire her artistry, and thinking, “what does it need? It needs something! But what? Ah! I know just the thing!”
And then she got to work.