Spiders were one of the first creatures that were able to successfully settle on land. The oldest arachnids are more than 400 million years old, almost twice the age of the first insects. Since their inception, all spiders have been and remain predators. However, at present there is only one (out of 42 thousand) species of spiders that feed on plant food.
It is difficult to overestimate the role of spiders in the ecological systems of the Earth. About a fifth of all insects are exterminated by spiders. Moreover, these are mainly harmful insects - flies, mosquitoes, various garden and field pests.
The spider is a universal predator, it possesses such a set of tools that no other creature from the world of arthropods (except for that small group of them, which is "imprisoned" specifically for hunting spiders) can not resist it in any way. The spider's senses are unrivaled in their class; if these are eyes, they provide an almost all-round view; if it is touch, then the spider senses the movement of the victim long before it is itself detected, and so on. Separately, it should be noted that spider venoms, which are at the same time digestive juices, do not have antidotes in the animal world and are dangerous for all animals without exception.
Recently, some researchers, having carefully examined the excellent adaptability of spiders for hunting and the techniques they use, come to very interesting conclusions. Changes in the climate of our planet caused by global warming lead to the fact that the habitats of many arachnids are expanding significantly, in addition, there are prerequisites for an increase in their size. And the fact is that, unlike insects, spiders, under the conditions that exist on Earth at the present time, can really reach enormous sizes.
Few thought, but insects make up the majority of the biomass of living things on our planet. Their success is explained by many factors: from the reliability of the life cycle to a sufficiently high fertility. For a long time it was not clear why insects are now so small, because they find the fossils of dragonflies with a wingspan of more than a meter.
The answer came when the insect respiratory apparatus was examined. It turned out that the size of the respiratory organs of insects - trachea - depends on the concentration of oxygen in the atmosphere. With the current composition of the atmosphere, where oxygen contains 21%, their size can be just that. The large size of insects implies a large size of the trachea, however, at the current oxygen concentration, they will work only with a relatively small part of them and the insect, lacking an oxidant, will simply die.
In spiders, the respiratory apparatus includes not only the trachea, but also the pulmonary sacs. And their size does not matter - the larger the spider, the more oxygen it can receive. That is, from the point of view of the respiratory system, the growth of spiders is not limited by anything. The same can be said about the nutrition of spiders - large individuals switch to larger food.
Previously, it was believed that the actions of spiders are purely instinctive and do not carry any signs inherent in more complex nervous activity. Indeed, the spider's brain contains from several hundred thousand to a million neurons - this is clearly not enough to talk about some kind of intelligence (the human brain, for example, contains hundreds of billions of neurons). However, the studies carried out allow us to assert that spiders have sufficiently developed mental abilities, which are found in primitive, and sometimes quite complex, chordate animals.
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It was noticed that some species of spiders, having met a certain prey for the first time, have difficulties in catching and eating it, however, for the second or subsequent times they cope with this task much more efficiently. Surprisingly, a similar situation happened not only with unnatural or accidental prey, but even with the one that is the natural food of the spider, for which it is "programmed" instinctively.
The situation with the weaving of the web was no less interesting. Spiders, whose web was torn apart by insects falling into it, weaved the next web with a smaller distance between the cells, thereby increasing its strength.
But the absolute discovery for scientists was the ability of some species of spiders to remember their "enemies" in the form of tools that annoyed them literally almost "in the face." For example, if you hit a spider once with a match, then every time it appears, the match will be attacked, even if several days have passed since their last contact. At the same time, the tweezers with which the spider is given food will always cause only a positive reaction in him.
The combination of all the factors considered: the ability to be large, the presence of the rudiments of the intellect, excellent senses and the unsurpassed skills of a predator make small spiders a rather serious enemy if suddenly something goes "wrong" in their evolution. And if a person is currently already successfully using modifications of viruses, who knows, perhaps in fifty years we will see the first results in the form of improved spiders, the size of a car wheel. A predator of this size is no longer just a "big nasty creature", but, in fact, a biological weapon.
But even without military use, such creatures are capable of doing a lot of misfortunes. Their appearance in any ecosystem will lead to a serious imbalance. In its class, it will be the dominant predator with the minimum number of enemies. And the absence of natural enemies and an abundance of food is the key to successful reproduction and prosperity.
What the appearance of giant arachnids can lead to, we can only guess. The possibility of a person having serious problems is not excluded. Of course, it will not reach our extinction, however, difficulties in life will definitely increase.