Tarantulas, belonging to the family Theraphosidae, are large spiders recognized by their size and dense covering of hair. These arachnids are found across many habitats, from deserts to rainforests. A common point of confusion is understanding how these spiders perceive the world, as their visual system is a collection of simpler visual organs rather than complex camera-like eyes.
The Standard Number of Tarantula Eyes
Tarantulas, like most spider species, possess a total of eight eyes. The eight eyes are a standard feature across the over 1,000 identified species of tarantulas, though the arrangement varies among different spider families. These visual sensors are located on the prosoma, the fused head and thorax section of the spider’s body. The collective arrangement provides an expansive field of view, which is more important for survival than forming sharp, detailed images.
How the Eyes Are Grouped
The eight eyes are clustered together on a small, raised structure on the carapace called the ocular tubercle. The eyes are organized into two distinct rows across this tubercle and are divided symmetrically into four pairs. The four central eyes are the anterior median eyes (AME) and posterior median eyes (PME), forming the main visual unit. Flanking these are the four lateral eyes (ALE and PLE), creating a wide-angle setup that provides nearly 360-degree coverage.
What Tarantula Vision Is Used For
Despite having eight eyes, tarantulas are quite nearsighted and lack sharp, detailed vision. Their eyes are simple ocelli, which are single lenses that lack the elaborate retinas found in vertebrates. This simple structure limits their ability to process fine visual information or form clear images. The primary function of the visual system is to detect changes in light intensity and sense motion. The eyes are effective at distinguishing between light and shadow, which triggers defensive or hunting behavior when detecting a predator or prey.
Tarantulas rely far more heavily on other sensory organs, especially the thousands of specialized hairs, or setae, covering their legs and bodies. These hairs are mechanoreceptors that detect subtle air currents and ground vibrations, providing detailed environmental information. A tarantula uses these vibrations to determine the size and location of potential prey. The eyes act as a supplemental detection system, while the highly sensitive hairs allow them to precisely locate and identify objects.