Spiders live all over the planet, in all countries. The spider brain occupies an average of a quarter of the volume of the body. Arachnophobia is one of the most common phobias in humans. Since spiders do not have ears, they hear sounds with the help of hairs growing on their legs. They smell in the same way - with sensitive hairs. The spider web can withstand stretching up to four hundred percent of its original length. Among some species of spiders, cannibalism is common.