Jumping Spider

The jumping spider family (Salticidae) contains more than 500 described genera and over 5,000 species, making it the largest family of spiders with about 13% of all species (Peng et al., 2002). Jumping spiders have good vision and use it for hunting and navigating. They are capable of jumping from place to place, secured by a silk tether. Both their book lungs and the tracheal system are well-developed, as they depend on both systems (bimodal breathing).

Jumping spiders live in a variety of habitats. Tropical forests harbor the most species, but they are also found in temperate forests, scrub lands, deserts, the intertidal zone (in Malaysia), even mountains (one species is reported to have been the spider collected at the highest elevation, on the slopes of Mt. Everest (Wanless, 1975).

Jumping spiders are generally recognized by their eye pattern. They typically have eight eyes arranged in three or four rows. The front, and most distinctive row is enlarged and forward facing to enable stereoscopic vision. The others are situated back on the cephalothorax.

Colors and patterns vary widely. Several species of jumping spiders appear to mimic ants, beetles, or pseudoscorpions. Others may appear to be parts of grass stems, bumps on twigs, bark, part of a rock or even part of a sand surface.

Jumping spiders are generally diurnal, active hunters. Their well developed internal hydraulic system extends their limbs by altering the pressure of body fluid (blood) within them. This enables the spiders to jump without having large muscular legs like a grasshopper. The jumping spider can therefore jump 20 to 60 or even 80 times the length of their body. When a jumping spider is moving from place to place, and especially just before it jumps, it tethers a filament of silk to whatever it is standing on. Should it fall for one reason or another, it climbs back up the silk tether.

Unlike almost all other spiders, they can quite easily climb on glass. Minute hairs and claws on their feet enable them to grip imperfections in the glass.

Jumping spiders also use their silk to weave small tent-like dwellings where females can protect their eggs, and which also serve as a shelter while moulting.

Jumping spiders are known for their curiosity. If approached by a human hand, instead of scuttling away to safety as most spiders do, the jumping spider will usually leap and turn to face the hand. Further approach may result in the spider jumping backwards while still eyeing the hand. The tiny creature will even raise its forelimbs and "hold its ground." Because of this contrast to other arachnids, the jumping spider is regarded as "curious" as it is interested in whatever approaches it.

Jumping spiders have very good vision centered in their anterior median eyes (AME). Their eyes are able to create a focused image on the retina, which has up to four layers of receptor cells in it (Harland & Jackson, 2000). Physiological experiments have shown that they may have up to four different kinds of receptor cells, with different absorption spectra, giving them the possibility of up to tetrachromatic color vision, with sensitivity extending into the ultra-violet range. It seems that all salticids, regardless of whether they have two, three or four kinds of color receptors, are highly sensitive to UV light (Peaslee & Wilson, 1989). Some species (for example, Cosmophasis umbratica) are highly dimorphic in the UV spectrum, suggesting a role in sexual signaling (Lim & Li, 2005). Color discrimination has been demonstrated in behavioral experiments.

The principal eyes have high resolution (11 min. visual angle), but the field of vision is narrow, from 2-5 degrees.

Because the retina is the darkest part of the eye and it moves around, one can sometimes look into the eye of a jumping spider and see it changing color. When it is darkest, you are looking into its retina and the spider is looking straight at you.
 

Jumping Spider Video

Jumping spiders capture their prey by jumping on it from several inches away, and they may jump from twig to twig or leaf to leaf. They can jump thirty times their body length. They can carry out complex maneuvers such as detours around obstacles in order to reach their prey. Their eyesight is much better than that of other spiders and most, if not all, insects. Most other spiders will only eat prey that they have captured live because they are unable to see dead prey (some long-legged sac spiders and anyphaenid sac spiders are exceptions as they recognize insect eggs as food) but jumping spiders will eat flies that have been killed for them. One jumping spider (Evarcha culicivora) is even known to only capture mosquitoes full of blood, using their eyesight and smell.

Even if there are no spiders that are pure herbivores, there are some jumping spiders which include nectar in their diet (Jackson et al., 2001). So far none are known to feed on pollen or seeds. When insects land on plants such as the partridge pea, which offers the spiders nectar through their extra floral nectaries, the jumping spiders help protect the plant in return by killing and eating insects that might damage the plant.

At least one species of jumping spiders, known as the Gliding Spider (Maratus volans) from Australia, has an abdomen with two wing-like flaps that can be tucked underneath it when not in use. When the spider is leaping, it can use its flaps to extend the jump and glide short distances through the air.

Some jumping spiders may bite to protect themselves if disturbed. However, jumping spiders usually escape and hide, and will only bite if provoked and cornered. While the bite of a larger jumping spider can be painful, only a few species produce any other effects. Almost all spiders (except hackled orb-weavers) have venom, but the venom of most spiders is not worse than the venom of a bee.

Jumping spiders use their vision in complex visual courtship displays. Males are often quite different in appearance than females and may have plumose hairs, colored or metallic hairs, front leg fringes, structures on other legs and other, often bizarre, modifications. These are used in visual courtship in which the colored or metallic parts of the body are displayed and complex sideling, vibration, or zigzag movements are performed in a courtship "dance." In recent years it has been discovered that many jumping spiders may have auditory signals as well, with amplified sounds produced by the males sounding like buzzes or drum rolls.