Some spiders make fanciful additions to their webs. While theories abound, scientists remain stumped by the creations.
Leave it to the spiders to do something that is compellingly beautiful and completely mysterious. Would we expect anything less? No.
The craft in question is the suitably Harry-Potteresque named phenomenon of stabilimentum – also known to us muggles and non-arachnologists as "web decoration."
Not all spiders spin webs, and even fewer spin webs ornamented with stabilimenta – so named because of an early theory that they were employed as a stabilizing device. There are a number of spider species in the families Araneidae, Tetragnathidae and Uloboridae that add some craft panache, but they are most common in the genus Argiope.
The existence of these silky squiggles has been noted in scientific literature for more than a century, yet there is still little agreement as to why they are created. Producing silk is not like, say, squirting Silly String from a can. A spider creates its silky strands from protein molecules and spends a lot of metabolic energy in the making of the patterns. So one thing seems certain, it's not a frivolous endeavor.
But scientists do have a few ideas. It could be for visibility, as a way to help steer birds and other animals from crashing into the precious construction. (For that I say, "thanks spiders!" because nobody likes a face full of spiderweb.) It could be used as a distraction to keep unsuspecting prey from seeing the hungry spider lurking in the shadows. It could actually lure prey in by reflecting ultraviolet light; or it could be used to hide the spider itself from predators. Who knows, it could just be a way for spiders to get rid of extra silk, some suggest.
Since the behavior has evolved independently a number of times, it's possible that it serves different functions for different species. I don't know, but if the spiders have come this far, maybe that can figure out some letters and write out a message and tell us what's going on here.