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CyberDodo and Spiders (1-56)

What do spiders eat?

Spiders are carnivorous predators that eat the prey they hunt in many ways. According to where spiders live, their diet is very wide, ranging from insects such as flies, mosquitoes, wasps, grasshoppers, butterflies and cockroaches, etc., to lizards or mice and tadpoles, frogs and even birds.

But spiders that cannot chew can only absorb liquids, so they must liquefy their prey by injecting venom into them (which contains digestive enzymes) because arachnids do not have a digestion process within their bodies (as with humans, for example) but externally (specialists call this process "lysis ).

It is important to note that unlike other mosquitoes and ticks, spiders do not feed on blood and are therefore not attracted to humans, which they consider, on the contrary, to be dangerous.

Are spiders useful?

In conjunction with the previous paragraph, it is no exaggeration to say that spiders are irreplaceable regulators, for example they get rid of insects, including mosquitoes. In this regard, they predate on insect pests, which should encourage us to treat them more leniently.

What is the geographical distribution of spiders?

There are spiders all over the surface of the planet, with the exception of frozen regions, the highest mountains and salt water because although it may seem unbelievable, there are even spiders that live in water!

For example, take the Argyroneta, which weaves a bell-shaped web and attaches it to aquatic plants and fills them with air, making trips to and from the surface. Located in a submarine shelter, she can then hunt all kinds of prey.

How many species of spiders are there?

Approximately 40,000, you can find them by clicking here (http://research.amnh.org/iz/spiders/catalog/INTRO3.html), the worldwide catalogue of spiders established by Norman I. Platnick from the American Museum of Natural History.

This scientific site - in English has a wealth of information on spiders, ranging from ‘Abacoproeces' to ‘Zyngoonops'.

Wasp Spider (Argiope bruennichi)

Are spiders dangerous?

Few spiders are dangerous to humans, firstly because, as we have seen, they avoid contact and most are too small to bite or even inject enough venom.

However, the bad reputation of black widows, brown recluse spiders and tarantulas is not overrated, because they represent a real danger to humans. The black widow and brown recluse because of their venom and tarantulas, because they rub the bristles on their abdomen and eject them when they feel attacked, which can cause severe allergic reactions.

Spider silk

The ability of spiders to produce silk is a marvel of evolution that deserves a whole CyberDodo casefile. The silk glands (sericteria) are located in the abdomen (Opthisoma), producing the silk which remains in liquid form when it is in the body of the spider.

The silk will come out of holes (usually 6 in number) located under the abdomen, which are called spinnerets. Upon contact with the air, the silk will solidify and the spider will be able to use it. Silk? It would be more correct to describe them as silks, because spiders are capable of producing several different types of silk, depending on the intended use.

For example, a very strong silk, which will support it as it spins its web and then another very sticky one with which it will weave the thread, etc. Note that when it is the same size, spider silk is stronger than steel.

The qualities of strength, lightness and elasticity of spider silk have been researched a great deal in order to produce it industrially for uses as diverse as fishing line or tennis racquet strings. The military is also interested in using it to create bulletproof vests.

This strong interest in this extraordinary silk has even led to research that may surprise the defenders of the environment. The cells of the spider silk glands and those of the mammary glands of goats are similar; goats have been manipulated genetically in Canada and the United States to make them produce fibroin (which is the basic protein of spider thread).

Have spiders completed their evolution?

This question would probably shock the famous English naturalist Charles Darwin (1809-1882), author of "The Origin of Species , which laid the foundations of evolutionary theory, yet the history of spiders enables us to ask this question.

The answer is obviously "no" because it is known, thanks to Charles Darwin, that natural selection is continuously at work and that all species are constantly under pressure from their environment so that the most adapted individuals survive and transmit their genes to the next generations.

So why ask? Because spider fossils (Plectreuridae), as old as 150 to 200 million years, were found in China and their exceptional state of preservation showed that their descendants of today are almost identical to them!