MadSci Network: Zoology |
Black widow eyes, while more numerous than those of humans, are much simpler than the human eye. These spiders are mostly active at night and thus they need eyes much less than humans do. In fact, despite their larger number of eyes, most spiders have rather minimal vision compared to humans, most only being able to distinguish between light and dark and some degree of movement. The exceptions are the jumping spiders (Salticidae), ogre-faced spiders(Deinopidae) and wolf spiders (Lycosidae), but in these cases the major part of the vision is in one pair of eyes, not in all eight. The number of receptors even in jumping spider eyes are not anywhere as high as in human eyes, being only around 1,000. Human eyes have over 100 million individual receptor cells in the retina. Thus spiders do not need the massive visual processing brain structure that we need. References: Foelix, R. F. 1996. Biology of spiders. 2nd ed. Oxford University Press, New York. How the Eye Works. http://www.lasereye.com/howeye.html
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