Do spiders have good eyesight?
Despite most having eight eyes, most spiders actually don’t have very good eyesight at all. Many are just able to detect major light intensity changes which stimulate their night-time web building and hunting activities.
Instead they focus their awareness on detecting movement and vibrations, so they can catch prey nearby. Your average garden spider lurks on flowers and spider webs and waits for a sign of movement. They have such a keen sense for vibration that they can detect prey in the surface of water, in the soil and in their silk threads. They can even detect changes in air pressure.
However, there are a few types of spiders who have specialized and developed good eyesight…
Hunting Spider Eyesight
There are three types of hunting spider who have good eyesight:
Jumping spider (Salticidae) are most active during the daytime. Their excellent eyesight enables them to hunt prey and recognize mates and enemies. Although they can leap 20 times their body length, attack jumps are small and precise. The jumping spider eyesight makes use of three different sets of eyes:
- Side eyes provide a blurry wide-angle image, triggered by the distant movement of prey.
- Middle front eyes turn in that direction and lock onto the prey, providing a clear telephoto image (probably in color).
- Front eyes judge the distance to the prey. When it comes within 2-3cm, the spider leaps and gets a feed.
Net-casting spiders (Deinopidae) can have eight eyes including two massive rear eyes. Their huge lenses face forward to give the spider a menacing appearance. Being so big, they are specialized for night vision (low light), taking in a wide field of view and gathering even the tiniest amount of light very efficiently. Indeed, net-casting spiders have better night-time eyesight than owls and cats.
Wolf spiders (Lycosidae) hunt in the moonlight, using four large posterior eyes lined with a highly reflective layer to help them see prey moving in the low light. Like cats, wolf spiders are easily spotted in direct torchlight because their reflective eyes shine right back at you.
So, do spiders have good eyesight? Generally no – but there are some arachnid families which have developed amazing vision in their own right.
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