Are they real?
Scientist Skye Long a doctoral student at the University of Massachusetts, Amherst, researched just that very question, in regards to spider eyes, anyway. Most spiders have lots of eyes, a total of 8 eyes all together. Long and fellow researchers wanted to find out just what purpose, if any, each pair of eyes has to a spider’s senses.
The Jumping Spider, known for its hunting abilities, doesn’t catch prey using a silk web, but just runs amuck and grabs it’s prey, like a boss. Jumper Spiders, being the top dogs of the arachnid world, have 8 eyes and were perfect candidates to be used in the research.
The study indicates that the main pair of spider eyes is for main details, while a pair on the side of its head may detect when something is moving in their direction. “We see that division of labor within that visual system,” Long told LiveScience. “That’s pretty cool if you think about it, because we only have one pair of eyes.”
Spidey Senses Tested
The two principal eyes of a spider located on the front of the spider’s head are called the anterior median eyes. This set of eyes carries the main stream of vision for a spider; complete with color vision and all. It can even detect UV light, which is much better vision than that of the human eye. The two eyes located on the outer sides of those median eyes are called the anterior lateral eyes, which seem to have a sort of “looming” response; the same response as humans when they duck after a ball comes at their face. These anterior lateral eyes were put to the test by Long and fellow researchers.
After having the jumping spider species of Phidippus Audax, in custody, researchers covered the different sets of eyes to test their functions. 16 spiders had their principal eyes covered, with green and orange colored paint, which is what would blind a spider. 14 spiders had their anterior lateral eyes covered, and 16 spiders were left paint free. These spiders where then placed in a sort of enclosure along with an iPod touch. The iPod had one black dot. When the spider was facing the screen, researchers would set the dot into motion. The dot would either shrink, as if moving away from the spider, or it would expand as if moving towards the spider.
Each group of spiders with different covered eyes exhibited different reactions. The spider control group, having no paint at all on its eyes, backed away from the iPod. The group of spiders with its principal eyes covered, leaving the anterior lateral eyes to do the seeing, also backed up when the dot was in motion. However, the group of spiders having their anterior lateral eyes covered, leaving the principal eyes exposed, didn’t detect any motion.
This makes the spider’s vision just a little more clear for us simple humans. Humans along with many other animals have just two eyes. With these two eyes multiple functions of vision must be carried out, while a spider spreads out all of those duties across all the lenses on its head.
Researcher Sky Long concludes his research by saying, “That gets us very deeply into how the spider is seeing the world. As close as it can get, really.”