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
Bird feet and legs the rear like the propeller on a motorboat. Grebes and many other waterfowl have shorter femur and a more or less narrow pelvis, too, which gives the impression that their legs are attached to the rear as in loons. Because avian forelimbs are wings, many forelimb functions are performed by the bill and hindlimbs. It has been proposed that the hindlimbs are important in flight as accelerators when taking-off. Some leg and foot functions, including conventional ones and those specific to birds, are: Typical toe arrangements in birds are: The most common arrangement is the anisodactyl foot, and second among