The science that studies arachnids is called arachnology. The most famous arachnologist was the French naturalist Eugène Simon, born in 1848. He died in 1924, but remains a highly respected expert. Simon described 4,000 species of spiders during his lifetime. Today, approximately 40,000 spider species are known, and new species are still being discovered. Spiders are classified into three suborders, with 144 families. The most well-known spider families are the Blakiston\’s spiders, Chrysoptera, and the step-spiders. Perhaps less well known are the species of Manga and Tegenaria.

The best known species, especially in the Czech Republic, are crustaceans, numbering about 2,600 species. As already mentioned, many crustacean spiders are found in the Czech Republic, as well as in North America and Asia. The largest species of spider is the glider, whose body size is 12 cm. The Czech Republic is also home to several species of glass spiders, which are classified as endangered. Stephnikites is a species of giant spider that lives mainly in Africa. A small number of this species also inhabits the Czech Republic and, like the glass hopper, is listed as endangered. However, arachnids do not include only spiders, as many believe. Arachnids are a large group of invertebrates, numbering 73,000 species and including, for example, mites, flagellates, and scorpions.

The largest number of species among the arachnids is in the tick order. Mites can be found in mattresses, sofas, carpets, or even in soft toys, making them a major enemy of humans, especially allergy sufferers. Mites can cause infections in both humans and animals. One of the most insidious mites is the scabies mite, which is a favorite parasite on the bodies and ears of animals. If medication is not administered in time to eliminate this mite, the animal will die. Whipworms are a type of spider found in tropical regions. The species resembles scorpions in appearance and behavior.