Spider's Web
Mangai, Chennai

Spiders are found world-wide on every continent except for Antartica.  More than 40,000 species and 100 families of spiders have been recorded.  They have been living on this earth for more than 100 million years.
Most spiders are harmless to humans but a few spider species, such as the "black widow" can bite humans and infect them with their venom.  Death from spider bites are however rare.
Spiders make their webs by producing silk-like threads. There are several glands located in the spider's abdomen which produce the silken thread.
Every gland produces a thread for a special purpose. There are seven different known glands and each spider possesses only some of these and not all together. They produce
 - sticky material for the thread
 - walking thread
 - attaching thread
 - thread for the encapsulation of prey
 - threads for cocoons
 - adhesive threads.
There are different kinds of webs: spiral orb webs, tangle webs or cobwebs, funnel webs, tubular webs (which run up the bases of trees or along the ground), sheet webs, etc.
When the web is deteriorated and is no longer useful, many spider species destroy it and eat up the threads so that they can recycle the raw silk material.
Dear children, shall we now see how a spider constructs a web? Let us look at the orb web which is the most common one.
Every web begins with a single thread which forms the basis of the rest of the structure. To establish the bridge, the spider climbs to a suitable starting point and it releases a length of thread into the wind. If the spider feels that the thread has caught onto something, it clinches up the silk and attaches it to a suitable place on its starting point. 
The spider then walks across the bridge thread, releasing a looser thread below it. The spider climbs to the centre of the loose thread and lowers itself down on a vertical thread to form a 'Y' shape.
Then it lays more frame threads between various anchor points as it walks along the structural threads. The spider lays out radius threads from the centre of the web to the frames. The spider lays more non-stick silk to form an auxiliary spiral extending from the centre of the web to the outer edge of the web.
Then it spirals inward, laying out sticky thread and using the auxiliary thread as a reference. The result is a web with non-sticky radius threads for the spider to walk around on, and a sticky spiral for catching bugs.
As we have seen earlier, the silk is made inside the glands of a spider's abdomen where it is a liquid. When it is drawn out of their spinnerets, it becomes thread-like. The silken thread is very strong--sturdier than a thread of steel that is of the same thickness.
Children, do you know which is the world's biggest and strongest spider web? It is found over a river in Madagaskar. Created by the 'Darwin Bark Spider', it can be as wide as 25 m. Occasionally, a group of spiders may build webs together in the same area. One such web was reported at Lake Tawakoni State Park in Texas, U.S.A., in  2007 and it measured 180 m.
Do You Know?
. The silky thread is also elastic. It can be stretched 30% to 40% before it breaks whereas steel can be stretched by only 8%. Even nylon can only be stretched by 20%.
. Many people are afraid of spiders: the abnormal fear of spiders is called "arachnophobia". Do you get scared of spiders? You need not, and should not!
. Spiders play a vital role in our eco-system. They catch many annoying and harmful insects for their prey. So spiders are generally not destructive but useful creatures.
Have you ever wondered how insects get stuck to a spider's web but the spider doesn't? Some spiders have two or three claws at the tip of each leg. In web-weaving spiders, one of these claws has a special area that is used for hooking on to the strands of the web. The spider can use this special claw to swing from strand to strand without having to touch the sticky part of the web. In this way, a spider can move quickly over its web without getting stuck.
As with the orb spider, most webs are made of at least two types of silk, the anchor silk (that the spider uses to move around on) and the sticky snare silk (that insects get stuck on). Just in case the spider slips, it has a special oily substance that helps to stop it getting stuck in its own web.
Next time when you see a spider, watch how it spins its web. By using threads, you can also try to construct a web. Do write to Jantar Mantar and let us know how successful you were!