A visit to the local science museum during BugFest a few weeks ago taught me (and my 5 year old) alot about spiders! We see spiders everywhere, and I imagine you do too. But this post isn't about spiders, it's about their webs.
Also known as cobwebs (from the latin word for spider - cobb), spider webs are made from a protein-based silk extruded from the spider's spinnerets. There are a variety of different web types, build for a variety of purposes. There are some types of spiders, such as crab and wolf spiders, that do not spin webs at all. Spider webs are such an important feature of spiders, it's used as a method of classifying spiders! In many of the web types below, some of the silk strands are sticky (for trapping prey), and some are not (so the spider can walk on them).
Funnel webs are commonly found on the ground. The are shaped like a horizontal sheet, angeled down into a funnel, leading to a hole where the spider stays. When a bug lands on the web, the spider feels the vibrations and rushes out to bite the bug, then drags it back into the hole for lunch. Picture below from itsnature.com
One of the most recognizable web types is the orb web, which many spiders build at night. this web type consists of a rectanglar frame forming the perimeter, a small hub in the center, a series of sticky radii joining the frame and hub, and finally a series of spirals around the hub. The spider senses vibrations that alerts it to the fact a bug has landed on the web and is ready for lunch. Picture below from National Geographic.
A sheet web has only a few strands of sticky silk but they are arranged in such a maze that it is very effective at trapping bugs. Once a bug is trapped, the spider pulls it through the web and wraps it up before enjoying lunch. Picture below from Australianmusem.net.
A tangleweb is generally a messy looking web with irregular borders made of sticky strands. The spiders that build these don't have teeth, so when they catch a bug, they wrap it up with silk and then suck it's blood out, leaving an empty carcas wrapped in silk. Photo below from backyardnature.
A very interesting special type of spider web is the communal web. These are giant webs shared by many spiders. This picture can make even a spider-lover queasy! Photo by Donna Garde (from badspiderbites).
Another example, from Lake Tawokoni in Texas. Photo from MSN.
Additional uses of spider silk include egg cases ( a couple different types), and drag-lines, which a spider lets out while it is walking or climbing. The dragline will help the spider find its way back or help it catch itself should it fall off something big! They also let out lines that get caught in the wind, propelling the spider to a new location (ballooning)! For more details check out this awesome website about spider silk.
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