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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, intertidal zones, and even mountains. Euophrys omnisuperstes is a species reported to have been collected at the highest elevation, on the slopes of Mt. Everest (Wanless, 1975). Certain species of Salticidae are quite common in Europe, such as the Zebra Jumping Spider Salticus scenicus, which is commonly found resting on sun-warmed stone or brick walls.
Jumping spiders are generally recognized by their eye pattern. They typically have eight eyes arranged in two or three 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 75-80 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 inquisitive as it is seemingly interested in whatever approaches it.
The four front eyes of an adult male Platycryptus undatus jumping spider (there are eight eyes total).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.
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