How can a spider weave its net between two high rising buildings far apart, or between trees several meters away from each other?”
The key is that spider silk is very lightweight and can float on the slightest currents of air. And spider silk is also sticky. A spider constructing a web might start by releasing a line of silk. This line is wafted by air currents and flaps in the breeze until it bumps into and sticks to a remote object. That might be a nearby tree or bush — or the side of a skyscraper.
Once the silk line is attached, some spiders will travel to its center and attach a second line. Ultimately, these spiders form a “T” or shallow “Y”, which becomes the hub of the final web. And it all starts with the fact that spider silk floats so easily. In fact, baby spiders use a behavior called “ballooning” to disperse. They send lines of silk out into the breeze, and easily float away.
That’s how spiders can end up just about anywhere — even the sides of skyscrapers many stories above the ground!
Arachnology (Lots of resources on silk and webs) – University of Antewerp
Books:
- Kozloff, E.N. (1990) Invertebrates. Saunders College Publishing. A subsidiary of Holt, Rhinehart, and Winston, INc.
Notes:
- It’s important to remember that all orb-weaving spiders instinctually know how to build their webs. In fact, you can experimentally blindfold a spider, and it still knows how to build a web.
- Web building varies between species, and it is genetically controlled.
- Spider silk has a higher tensile strength than any other natural material tested thus far. It also has a stronger tensile strength than any metal (Kozloff).
- Orb weavers often build white, gauzy “zippers” into their webs. The purpose of these is not well understood, but they may serve to alert birds or mammals to the web’s presence. Webs are very costly to build and if the spider can deter a bird or mammal from breaking its web, it would be beneficial.
- Spider silk is made of protein. This is very energetically expensive for the spider to make. So much so that spiders usually eat the silk (and consume the nutrients) of an old web before building a new one. Many spiders build a new web every day.
- Some species in the tropics build communal webs high in the trees.
- More primitive species of spider may also use primitive web building behaviors–some spiders reside in a hole in the ground and send out “trap lines” or “trip lines” that can catch passing insects or other prey.
