Learn Something: Stabilimentum

A couple of weeks ago I had the opportunity to take a trip through Nevada, California, Oregon and Washington with the geology department where I work. It was so much fun! While they were studying the rocks (which I learned a lot about as well) I encountered some pretty big orb weaver spider webs; namely this one here:

Can you see it? It blends in pretty well as cameras aren't awesome at picking up webs.

Anyway, that night at the hotel I decided to go back and do some more research on orb weavers and more specifically their webs. Which lead me to stumble upon something really cool called the "stabilimentum" or, a bit easier to remember, "web decoration." I'm gonna start out right away by saying that the function of these web decorations is still a huge matter of debate. Originally they were thought to be built to stabilize the web (hence 'stabilimentum') but that theory has long since been dismissed. What got my attention is how dang cool these things look. (If you have a distaste of spiders maybe don't continue)

(Images found on google/wikipedia)

Aren't those beautiful? No wonder they call them decorations. They're pretty cool. Depending on the species of spider, these can be made out of silk, egg sacs, or debris. This is one of the reasons there is so much debate about their function, they are made in so many different ways and with so many different patterns! For this reason, it is assumed that different species may create them for different purposes. The theories are wide ranging and include

• Camouflage: (the thick banding breaks up the form of the spider)
• Reflection of sunlight (to keep birds and other larger creatures from running into the web)
• Vibration amplifier
• Thermoregulation (regulation of temperature)
• Attract insects
• Stress
• Get rid of extra silk
• Aesthetics
• To attract male species (the stabilimentum would show that the female is ready to mate)

The oxford journal also pointed out that spiders do not always create these web decorations, showing that there may be a large cost and effort included in making them. 

Another fun fact: orb weavers that actually do build webs will often eat their web every night, rest for an hour, and then build a new one in the same general area. This is the reason that their webs are so often clear of detritus; unlike other spiders such as the black widow.