Eyes and Functions
Most copepods have a single compound eye in the middle of their head, but this copepod, of the family Corycaeus, possesses two large cuticular lenses paired to form a telescope. Like most spiders, this wolf spider has eight simple eyes, two main eyes at the front and six smaller secondary eyes. The main eyes form images. The secondary eyes detect peripheral movement, and have a reflective tapetum lucidum which improves night vision. Holochroal eye of an Early Devonian trilobite Paralejurus sp. Schizochroal eye of a Devonian trilobite from the family Calmoniidae Horseshoe crabs have two primary compound eyes and seven secondary simple eyes. Two of the secondary eyes are on the underside.Most arthropods have at least one of two types of eye: lateral compound eyes, and smaller median ocelli, which are simple eyes. When both are present, the two eye types are used in concert because each has its own advantage. Flying insects can remain level with either type of eye surgically removed, but the two types combine to give better performance. Ocelli can detect lower light levels, and have a faster response time, while compound eyes are better at detecting edges and are capable of forming images.
Further information: Compound eye Further information: OcellusRead more about this topic: Arthropod Eye
Famous quotes containing the words eyes and, eyes and/or functions:
“When I am on a stage, I am the focus of thousands of eyes and it gives me strength. I feel that something, some energy, is flowing from the audience into me. I actually feel stronger because of these waves. Now when the play’s done, the eyes taken away, I feel just as if a circuit’s been broken. The power is switched off. I feel all gone and empty inside of me—like a balloon that’s been pricked and the air’s let out.”
—Lynn Fontanne (1887–1983)
“The big blue eyes are shut which saw wrong clothing
And favourite fields and coverts from a horse;”
—Sir John Betjeman (1906–1984)
“Nobody is so constituted as to be able to live everywhere and anywhere; and he who has great duties to perform, which lay claim to all his strength, has, in this respect, a very limited choice. The influence of climate upon the bodily functions ... extends so far, that a blunder in the choice of locality and climate is able not only to alienate a man from his actual duty, but also to withhold it from him altogether, so that he never even comes face to face with it.”
—Friedrich Nietzsche (1844–1900)