| Jumping spiders Temporal range: Eocene[1] - Present |
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| An adult female Phidippus mystaceus jumping spider | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| Class: | Arachnida |
| Order: | Araneae |
| Section: | Entelegynae |
| Family: | Salticidae Blackwall, 1842 |
| Subfamilies | |
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Aelurillinae |
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| Diversity | |
| 553 genera, 5025 species | |
| The jumping spider family (Salticidae) contains more than 500 described genera and about 5,000 described species,[2] making it the largest family of spiders with about 13% of all species.[3] Jumping spiders have some of the best vision among invertebrates and use it in courtship, hunting and navigation. Though they normally move quietly and fairly slowly, most species are capable of very agile jumps, notably when hunting, but sometimes in response to sudden threats. Both their book lungs and the tracheal system are well-developed, and they use both systems (bimodal breathing). Jumping spiders are generally recognized by their eye pattern. All jumping spiders have four pairs of eyes with very large anterior median eyes. |
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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 Mount Everest.[4]
Jumping spiders have very good vision centered in their anterior median eyes (AME). These 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 ultraviolet 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, anterior median, eyes have high resolution (11 min. visual angle),[5] but the field of vision is narrow, from 2 to 5 degrees. However, the retina at the back of the tube-shaped anterior median eye can move to inspect objects off the direct axis of vision. This dynamic adjustment is a means of compensation for the narrowness of the static field of vision. It is analogous to the way most primates move their eyes to focus images of interest onto the fovea centralis. Such movements within the jumping spider's eyes are visible from outside when the attention of the spider is directed to various targets.[6] It is not clear whether they use their lateral eyes for anything but reaction to threats, but they certainly do react to movement well to either side, and apparently out of view of the anterior median eyes.
Jumping spiders are generally diurnal, active hunters. Their well-developed internal hydraulic system extends their limbs by altering the pressure of body fluid (hemolymph) within them. This enables the spiders to jump without having large muscular legs like a grasshopper. Most jumping spiders can jump several 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 (or dragline) to whatever it is standing on. Should it fall for one reason or another, for example if the prey shakes it off, it climbs back up the silk tether. Some species, such as Portia will actually let themselves down to attack prey such as a web spider apparently secure in the middle of its web. Like many other spiders that leave a practically continuous silk trail, jumping spiders impregnate the silk line with pheromones that play a role in social and reproductive communication, and possibly in navigation.
Jumping spiders can learn, recognize, and remember colors.[7]
Jumping spiders are generally active hunters, which means that they do not as a rule rely on a web to catch their prey. Instead, these spiders usually stalk their prey, though some species, in particular some in the genus Portia do spin functional prey capture webs, though not structures as impressive as say, the typical orb webs of the Araneidae. They use their superior eyesight to distinguish and track their intended meals, often for several inches. Then they pounce and administer a venomous bite. The venom acts very quickly, giving the insect little time to react before succumbing.[8] They can use the silk tether in hunting, to enable them to attack prey that otherwise would be inaccessible. For example, by advancing towards the prey to less than the jumping distance then retreating and leaping in a arc at the end of the tether line, many species can leap onto prey on vertical or even on inverted surfaces, which of course in a gravitational field would not be possible without such a tether.
Some species, particularly in the genus Portia exhibit both varied innate hunting behavior and adaptive behavior to match the circumstances, and can stalk prey by devious routes that take them out of sight of the prey for considerable distances, to a degree surprising to observe in such small-brained invertebrates.
Although jumping spiders are generally carnivorous, many species have been known to include nectar in their diet,[9] and one species, Bagheera kiplingi, feeds primarily on plant matter.[10] None is known to feed on seeds, nor fruit. Plants such as the partridge pea offer the jumping spiders nectar through extrafloral nectaries, and in return the spiders help to protect the plant by killing and eating pests.
Jumping spiders use their vision in complex visual courtship displays. Males are often quite different in appearance from females, and may have plumose hairs, colored or iridescent hairs, front leg fringes, structures on other legs, and other, often bizarre, modifications. These are used in visual courtship in which the colored or iridescent parts of the body are displayed and complex sideling, vibrational, or zigzag movements are performed in a courtship "dance". If the female is receptive to the male she will assume a passive, crouching position. In some species, the female may also vibrate her palps or abdomen. The male will then extend his front legs towards the female to touch her. If the female remains receptive, the male will climb on the female's back and inseminate her with his palps.[11]
A 2008 study of the species Phintella vittatain in Current Biology suggests that female spiders react to the male reflecting ultraviolet B light before mating, a finding that challenges the previously held assumption that animals did not register ultraviolet B light.[12] 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.[13]
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Jumping spider classification
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The monophyly of the family Salticidae is well established through both phylogenetic and morphological analyses. There is, however, no consensus on what other group of spiders are most closely related to the jumping spiders. Suggested sister groups have included the oxyopids (lynx spiders), thomisids (crab spiders), clubionoids (sac spiders), and web building spiders.[14]
Jumping spiders can be divided into three major lineages: the lyssomanines (subfamily Lyssomaninae), the spartaeines (subfamily Spartaeinae), and the salticoids (unranked clade Salticoida).[14] Of these, Salticoida accounts for over 90% of all jumping spider species. Salticoida can be further divided into numerous groups including Amycoida, Astioida, Aelurilloida, Euophryinae, Heliophaninae, Marpissoida, and Plexippoida.[14]
Very few jumping spider fossils have been found. Of those that are known, all are from Cenozoic era amber. The oldest fossils are from Baltic amber dating to the Eocene epoch, specifically, 54 to 42 Ma (million years ago). Other fossil jumping spiders have been found in Chiapas amber and Dominican amber.[1]