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CyberDodo and Spiders (1-56)

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This is a curious yet appropriate question, since we identify insects because they have 6 legs and yet spiders have 8. Furthermore, insects mainly have a body composed of 3 parts, but spiders only have 2. So, contrary to what many people think, spiders are not insects, they belong to the class of arachnids (Aranae).

What are the main characteristics of spiders?

We already know that they have 8 legs and a body divided into two parts, beginning with the anterior (front), which is called the prosoma or cephalothorax (That is, the "head" and "chest") which houses the brain, eyes (most often it has 8 of them), a stomach, a "mouth" which is surrounded by two pairs of "tools", firstly the chelicerae ending in hooks with which the spider bites its prey and injects its venom and, secondly, the pedipalps which are used to recognise and catch prey. The 8 legs are also attached to the cephalothorax .

The posterior (rear) is called the opisthosoma or simply the abdomen. It contains the lungs, heart, liver, sexual organs and glands that produce silk.

The front and rear are interconnected by a much thinner section: the pedicel, which contributes to the flexibility of the spider's body.

Are males and females the same size?

There may be some species of spiders with large physical differences, where the male is much smaller than the female. This is significant sexual dimorphism.

Are spiders hairy?

Not only are they hairy, but they are covered by different types of hairs. These are proper sense organs which transmit a great deal of information about their environment, here is a non-exhaustive list of examples:

- Trichobothrias are sensitive to movement in the air and help them to identify things such as a fly in flight

- Bristles act as sensors for vibrations in their nets, which is very useful when an insect has been trapped

- Other hairs function as laboratories that will analyse the ambient molecules, they are proper chemoreceptors.

Surprising as this may seem, it is not inconsistent to say that their hairs transmit more information to spiders than their eyes, even though most of them have 8.

Spiders are predators of rare efficiency

Why do spiders molt?

Because, unlike humans, for example, they have no 'internal skeleton", but an outside one, which is called an exoskeleton. This means that as they grow, they find themselves cramped in a hard cuticle which can not stretch. The only solution is to shed the old skin regularly for a new one, this operation is called molting. For most spider species, this happens a dozen times during their lives.

How does molting take place? When its exoskeleton becomes too small, the spider finds a safe place and makes it "crack". It then sheds its old skin with varying degrees of difficulty and taking advantage of the lack of stress, it increases in volume. The new skin will harden quickly, but during this time, it is particularly vulnerable to predators.

It sheds its old skin, which experts call "exuviae" and is often confused with a dead spider.

What is autotomy?

This is the impressive ability that spiders have to cut off a member in case of necessity! This amputation does not occur in just any way but so as not to endanger its life. In addition, it can regenerate the lost limb at its next molt.

How do spiders reproduce?

Most of the time, it's a tragic story for the male which will not survive. It will first produce sperm that is ejaculated onto a web that has been specially woven for this purpose. Then it transfers and stores it in bulbs (Called copulatory bulbs) located at the end of its pedipalps. The male is now ready to fertilise a female, but he must find her, to do this, pheromones will guide him as surely as a light in the night.

Pheromones are chemical substances produced by the body of most species, which are used to attract partners for the purpose of reproduction. The organs that allow spiders to receive and identify these chemical messages are located at the end of their legs.

Once the male has found the female, after a mating ritual specific to their species, they will mate. This is the introduction of the male copulatory bulbs into the female reproductive tract. Note that the shape of their respective sexual organs is unique to each species and prohibits reproduction between different species.

The end of copulation means death or at least a shortened life cycle for the male, who will either be devoured by the female, or die. For the female, the reproductive cycle is just beginning and depending on the species, she will lay eggs and abandon them (they are wrapped in a cocoon of silk), others keep them on their webs or even on themselves.

Spiders are oviparous, the number of eggs varies greatly from one species to another (from one to thousands).

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