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Insects and other arthropods


Araneidae web, Québec, Canada.
Photo: Insectarium de Montréal (Gilles Murray)
Araneidae web, Québec, Canada.
  • Araneidae web, Québec, Canada.
  • Araneidae, Québec, Canada.
  • Araneidae, Québec, Canada.
  • Spider, Québec, Canada.
  • Argiope aurantia, Québec, Canada.

A spider’s web is an efficient passive trap used to catch insects. The insects unwittingly blunder into the trap and remain stuck in the silk threads until the spider comes to paralyze and eat them. Most webs are spun by species in the Araneidae family.

Not all of the threads in a web are sticky. The threads that form its rays are not. Only the silk that forms the spiral is sticky. The vibrations created by the insect as it tries to escape from the web alert the spider to its presence. The spider has special anti-adhesive hairs on its legs and travels only along the non-sticky threads so that it doesn’t get caught in its own trap.

Some spiders produce silk threads that are made of the most resistant material known on the planet. These threads are stronger than steel of the same thickness! Their elasticity is also remarkable – they can be stretched to two times their length without breaking.

Spinning a spiral orb web

The construction of a web begins with its first thread, which runs horizontally. The spider may throw a thread into the wind from a point above and wait until the thread attaches to vegetation. It then pulls the thread until it is as horizontal as possible. The spider may also place the first thread by attaching it to point A and pulling it along to point B.

Once the first thread is secure, the spider travels along it with a new thread that it will attach to the opposite side (from A to B).

The spider returns to the centre of the floating web, where it attaches a third thread (C) that it pulls to the bottom, down to point D, and attaches it there. These three threads form a Y that is the centre of the web.

The Y-shaped structure allows the spider to travel along it at random. It spins and pulls threads to create a radial structure that resembles the spokes of a bicycle wheel, which reinforces the centre of the web.

Once the spokes are consolidated and its tensions are balanced, the spider spins a new spiral from the inside to the outside. This temporary spiral consolidates the entire web. Up to this point, none of the threads are sticky.

Finally, the spider traces its steps backwards, from the outside to the inside, and spins sticky threads to create a final spiral whose spokes are much closer together. On its return trip, the spider eats the temporary spiral for the proteins of which the silk is composed.

The web may be respun in the morning or the evening, in about the same place, depending on whether the spider is diurnal or nocturnal. The web takes about an hour to spin. The old web is not destroyed though – the spider eats it before respinning its new web.

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