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The underside and head of a female spider. Spiders, unlike insects, have only two main body parts ( tagmata) instead of three: a fused head and thorax (called a cephalothorax or prosoma) and an abdomen (also called an opisthosoma ). The exception to this rule are the assassin spiders in the family Archaeidae, whose cephalothorax is divided into ...
Spider vision. Hogna wolf spider (family Lycosidae) showing the enlarged posterior median eyes typical of the family. The eyes of spiders vary significantly in their structure, arrangement, and function. They usually have eight, each being a simple eye with a single lens rather than multiple units as in the compound eyes of insects.
The retina (from Latin rete 'net'; pl. retinae or retinas) is the innermost, light-sensitive layer of tissue of the eye of most vertebrates and some molluscs.The optics of the eye create a focused two-dimensional image of the visual world on the retina, which then processes that image within the retina and sends nerve impulses along the optic nerve to the visual cortex to create visual perception.
The tapetum lucidum ( Latin for 'bright tapestry, coverlet'; / təˈpiːtəm ˈluːsɪdəm / tə-PEE-təm LOO-sih-dəm; pl.: tapeta lucida) [ 1] is a layer of tissue in the eye of many vertebrates and some other animals. Lying immediately behind the retina, it is a retroreflector. It reflects visible light back through the retina, increasing ...
Anatomy of the avian eye. The main structures of the bird eye are similar to those of other vertebrates.The outer layer of the eye consists of the transparent cornea at the front, and two layers of sclera — a tough white collagen fibre layer which surrounds the rest of the eye and supports and protects the eye as a whole.
The scleral ring is a hardened ring of plates, often derived from bone, that is found in the eyes of many animals in several groups of vertebrates. Some species of mammals, amphibians, and crocodilians lack scleral rings. [ 1] The ring is in the fibrous outer layer of the eye, called the sclera. The structure is commonly referred to as the ...
Most birds have approximately 175 different muscles, mainly controlling the wings, skin, and legs. Overall, the muscle mass of birds is concentrated ventrally. The largest muscles in the bird are the pectorals, or the pectoralis major, which control the wings and make up about 15–25% of a flighted bird's body weight.
Argiope aurantia is a species of spider, commonly known as the yellow garden spider, [2] [3] black and yellow garden spider, [4] golden garden spider, [5] writing spider, zigzag spider, zipper spider, black and yellow argiope, corn spider, Steeler spider, or McKinley spider. [6] The species was first described by Hippolyte Lucas in 1833.