The Ecology of Humans (15-19) Jumping Spiders

 Jumping Spiders

Propelled by their back legs, jumping spiders can leap over 20 times their body length. But when pouncing on prey, they make short, accurate leaps.

Jumping spiders are most active during the day. They have excellent vision: able to hunt prey as well as recognize mates and enemies.

Physically separate sets of eyes cooperate. ~ American arachnologist Elizabeth Jakob

While hunting, jumping spiders can see in 3 ways using 3 different pairs of eyes. 1) Movement of a distant prey may be detected by side eyes or rear eyes, which give a blurry wide-angle image. 2) Once a prey is sensed, a jumping spider turns in that direction, locking on with its large, middle front eyes. These main anterior eyes can only see what is front of them. With 4 distinct layers of light-sensitive receptors, these eyes provide a clear, telephoto-focused, rich color image.

The spider tracks prey both by moving its body and by using muscles to swivel the elongated eye capsules so that the light-sensitive retina stays locked on target. 3) As the spider closes in, its side eyes judge distance. Once within 2–3 cm, the spider jumps its prey.

The principal eyes of jumping spiders have a unique retina with 4 tiered photoreceptor layers, on each of which light of different wavelengths is focused by a lens with appreciable chromatic aberration. ~ Japanese biologist Takashi Nagata et al