Eyes of the spiders

1999/11/01 Elhuyar Zientzia Iturria: Elhuyar aldizkaria

• Zoologia

A group of Swedish researchers discover that one of the three walls of the European common spider (Drassodes cupreus) uses it for non-visual but reference purposes. This pair of eyes is located in the cephalothorax of the spider, at the top of the head. They are blue, have no lenses and can't form any image.

Instead, they have filters that can detect the polarization of light. The axes of these two eyes are perpendicular and illuminate alternately. The spider seems to find its way by comparing the difference of luminosity of the eyes. There may be more spiders with this capacity. Their discovery could determine the functions of the secondary eyes of spiders.