predators to prevent being attacked and killed by the female spider. Physiology Vision L. arenicola have eight eyes, with four eyes on the anterior side of the carapace and four on the posterior side. Based on their position, the eyes fall under the name anterior median eyes (AMEs), anterior lateral eyes (ALEs), posterior median eyes (PMEs), or the posterior lateral eyes (PLEs). AMEs are the main eyes, while the others are considered secondary eyes. AMEs are classified as principal eyes because they have a reversed retina with muscles that have control over the direction and magnitude of the receptive field, while ALEs, PMEs, and PLEs have no muscular retinal control and an inverse retina with a reflecting tapetum behind it which aids in night vision. Visual fields The visual fields of the lateral eyes (ALEs and PLEs) are elongated along a horizontal plane and overlap. This allows the spiders to have an extensive receptive field across the horizontal plane. AMEs had circular visual fields that appear to be forward looking and also overlapped, while PMEs have overlapping visual fields that integrates upper planes of sight. Together these visual fields produce a full panoramic visualization of the spider's surroundings. AMEs, PLEs, and ALEs are involved in nocturnal navigation, while PMEs are not. Role of vision in nocturnal navigation Although seismic communication via drumming and other vibrational mechanisms assist in navigation in the dark, vision is a major factor in nocturnal navigation. This differs from other spider species, in which vision does not play a significant role in nocturnal visualization. L. arenicola have visual fields that span an entire panoramic visualization of surroundings. The spider’s eight eyes assist in this ability to visualize one’s surroundings. Each eye is enabled to specialize and fine tune its function for specific visual tasks. In the case of L. arenicola, this specialization is in navigation. Eyes are composed of one photopigment that best captures light of about 550 nm. However, they have weak temporal resolution in dark conditions. In order to be able to see at night, L. arenicola use temporal summation for navigation across the dunes. Temporal summation of visual stimuli allows multiple stimuli to be integrated to capture visual information in dim lighting. The disadvantage to this adaptation is that quickly-moving object cannot be seen, since each temporal sum takes about 1 second. References External links Hallan, Joel 2006: Synopsis of the Described Araneae