Spider Spider Spiders (order Araneae) are air-breathing arthropods that have eight legs and chelicerae with fangs able to inject venom. They are the largest order of arachnids and rank seventh in total species diversity among all other orders of organisms. Spiders are found worldwide on every continent except for Antarctica, and have become established in nearly every habitat with the exceptions of air and sea colonization. , at least 45,700 spider species, and 113 families have been recorded by taxonomists. However, there has been dissension within the scientific community as to how all these families should be classified, as evidenced by
History of Animals especially the wryneck, fishes and snakes. Book III The internal organs, including generative system, veins, sinews, bone etc. He moves on to the blood, bone marrow, milk including rennet and cheese, and semen. Book IV Animals without blood (invertebrates) – cephalopods, crustaceans, etc. In chapter 8, he describes the sense organs of animals. Chapter 10 considers sleep and whether it occurs in fish. Books V and VI Reproduction, spontaneous and sexual of marine invertebrates, birds, quadrupeds, snakes, fish, and terrestrial arthropods including ichneumon wasps, bees, ants, scorpions, spiders, and grasshoppers. Book VII Reproduction of man, including puberty, conception, pregnancy, lactation,