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Spiders (order Araneae) are air-breathing arthropods that have eight legs and chelicerae with fangs that inject venom. They are the largest order of arachnids and rank seventh in total species diversity among all other groups of organisms.^1] Spiders are found worldwide on every continent except for Antarctica, and have become established in nearly every habitat with the exception of air and sea colonization. As of 2008, approximately 40,000 spider species, and 109 families have been recorded by taxonomists;^[2] however, there has been confusion within the scientific community as to how all these families should be classified, as evidenced by the over 20 different classifications that have been proposed since 1900.^[3]

A natomically, spiders differ from other arthropods in that the usual body segments are fused into two tagmata, the cephalothorax and abdomen, and joined by a small, cylindrical pedicel. Unlike insects, spiders do not have antennae. In all except the most primitive group, the Mesothelae, spiders have the most centralized nervous systems of all arthropods, as all their ganglia are fused into one mass in the cephalothorax. Unlike most arthropods, spiders have no extensor muscles in their limbs and instead extend them by hydraulic pressure.

Their abdomens bear appendages that have been modified into spinnerets that extrude silk from up to six types of silk glands within their abdomen. Spider webs vary widely in size, shape and the amount of sticky thread used. It now appears that the spiral orb web may be one of the earliest forms, and spiders that produce tangled cobwebs are more abundant and diverse than orb-web spiders. Spider-like arachnids with silk-producing spigots appear in the Devonian period about 386 million years ago, but these animals apparently lacked spinnerets. True spiders have been found in Carboniferous rocks from 318 to 299 million years ago, and are very similar to the most primitive surviving order, the Mesothelae. The main groups of modern spiders, Mygalomorphae and Araneomorphae, first appear in the Triassic period, before 200 million years ago.

A herbivorous species, Bagheera kiplingi, was described in 2008,^[4] but all other known species are predators, mostly preying on insects and on other spiders, although a few large species also take birds and lizards. Spiders use a wide range of strategies to capture prey: trapping it in sticky webs, lassoing it with sticky bolas, mimicking the prey to avoid detection, or running it down. Most detect prey mainly by sensing vibrations, but the active hunters have acute vision, and hunters of the genus Portia show sign s of intelligence in their choice of tactics and ability to develop new ones. Spiders' guts are too narrow to take solids, and they liquidize their food by flooding it with digestive enzymes and grinding it with the bases of their pedipalps, as they do not have true jaws.

Male spiders identify themselves by a variety of complex courtship rituals to avoid being eaten by the females. Males of most species survive a few matings, limited mainly by their short life spans. Females weave silk egg-cases, each of which may contain hundreds of eggs. Females of many species care for their young, for example by carrying them around or by sharing food with them. A minority of species are social, building communal webs that may house anywhere from a few to 50,000 individuals. Social behavior ranges from precarious toleration, as in the aggressive widow spiders, to co-operative hunting and food-sharing. Although most spiders live for at most two years, tarantulas and other mygalomorph spiders can live up to 25 ye ars in captivity.

While the venom of a few species is dangerous to humans, scientists are now researching the use of spider venom in medicine and as non-polluting pesticides. Spider silk provides a combination of lightness, strength and elasticity that is superior to that of synthetic materials, and spider silk genes have been inserted into mammals and plants to see if these can be used as silk factories. As a result of their wide range of behaviors, spiders have become common symbols in art and mythology symbolizing various combinations of patience, cruelty and creative powers.

Description

Body plan

Spiders are chelicerates and therefore arthropods.[6] As arthropods they have: segmented bodies with jointed limbs, all covered in a cuticle made of chitin and proteins; heads that are composed of several segments that fuse during the development of the embryo.^[5] Being chelicerates, their bodies consist of two tagmata, sets of segments that serve similar functions: the foremost one, called the cephalothorax or prosoma, is a complete fusion of the segments that in an insect would form two separate tagmata, the head and thorax; the rear tagma is called the abdomen or opisthosoma.^[6] In spiders the cephalothorax and abdomen are connected by a small cylindrical section, the pedicel.^[7] The pattern of segment fusion that forms chelicerates' heads is unique among arthropods, and what would normally be the first head segment disappears at an early stage of development, so that chelicerates lack the antennae typical of most arthropods. In fact chelicerates' only appendages ahead of the mouth are a pair of chelicerae, and they lack anything that would function directly as "jaws".^[5][8] The first appendages behind the mouth are called pedipalps, and serve different functions within different groups of chelicerates.^[6]

Spiders and scorpions are members of one chelicerate group, the arachnids.^[8] Scorpions' chelicerae have three sections and are used in feeding.^[9] Spiders' chelicerae have two sections and terminate in fangs that are generally venomous, and fold away behind the upper sections while not in use. The upper sections generally have thick "beards" that filter solid lumps out of their food, as spiders can take only liquid food.^[7] Scorpions' pedipalps generally form large claws for capturing prey,^[9] while those of spiders are fairly small appendages whose bases also act as an extension of the mouth; in addition those of male spiders have enlarged last sections used for sperm transfer.^[7]

In spiders the cephalothorax and abdomen are joined by a small, cylindrical pedicel, which enables the abdomen to move independently when producing silk. The upper surface of the cephalothorax is covered by a single, convex carapace while the underside is covered by two rather flat plates. The abdomen is soft and egg-shaped. It shows no sign of segmentation, except that the primitive Mesothelae, whose living members are the Liphistiidae, have segmented plates on the upper surface.^[7]

Circulation and respiration

Like other arthropods, spiders are coelomates in which the coelom is reduced to small areas round the reproductive and excretory systems. Its place is largely taken by a hemocoel, a cavity that runs most of the length of the body and through which blood flows. The heart is a tube in the upper part of the body, with a few ostia that act as non-return valves allowing blood to enter the heart from the hemocoel but prevent it from leaving before it reaches the front end.^[11] However, in spiders it occupies only the upper part of the abdomen, and blood is discharged into the hemocoel by one artery that opens at the rear end of the abdomen and by branching arteries that pass through the pedicle and open into several parts of the cephalothorax. Hence spiders have open circulatory systems.^[7] The blood of many spiders that have book lungs contains the respiratory pigment hemocyanin to make oxygen transport more efficient.^[8]

Spiders have developed several different respiratory anatomies, based on book lungs, a tracheal system, or both. Mygalomorph and Mesothelae spiders have two pairs of book lungs filled with haemolymph, where openings on the ventral surface of the abdomen allow air to enter and diffuse oxygen. This is also the case for some basal araneomorph spiders like the family Hypochilidae, but the remaining members of this group have just the anterior pair of book lungs intact while the posterior pair of breathing organs are partly or fully modified into tracheae, through which oxygen is diffused into the haemolymph or directly to the tissue and organs.^[7] The trachea system has most likely evolved in small ancestors to help resist desiccation.^[8] The trachea were originally connected to the surroundings through a pair of openings called spiracles, but in the majority of spiders this pair of spiracles has fused into a single one in the middle, and moved backwards close to the spinnerets.^[7] Spiders that have tracheae generally have higher metabolic rates and better water conservation.^[12]

Feeding, digestion and excretion

Uniquely among chelicerates, the final sections of spiders' chelicerae are fangs, and the great majority of spiders can use them to inject venom into prey from venom glands in the roots of the chelicerae.^[7] The family Uloboridae has lost its poison glands, and is killing the prey with silk instead. Like most arachnids including scorpions,^[8] spiders have a narrow gu t that can only cope with liquid food and spiders have two sets of filters to keep solids out.^[7] They use one of two different systems of external digestion. Some pump digestive enzymes from the midgut into the prey and then suck the liquified tissues of the prey into the gut, eventually leaving behind the empty husk of the prey. Others grind the prey to pulp using the chelicerae and the bases of the pedipalps, while flooding it with enzymes; in these species the chelicerae and the bases of the pedipalps form a preoral cavity that holds the food they are processing.^[7]

The stomach in the cephalothorax acts as a pump that sends the food deeper into the digestive system. The mid gut bears many digestive ceca, compartments with no other exit, that ex tract nutrients from the food; most are in the abdomen, which is dominated by the digestive system, but a few are found in the cephalothorax.^[7]

Most spiders convert nitrogenous waste products into uric acid, which can be excreted as a dry material. Malphigian tubules ("little tubes") extract these wastes from the blood in the hemocoel and dump them into the cloacal chamber, from which they are expelled through the anus.^[7] Production of uric acid and its removal via Malphigian tubules are a water-conserving feature that has evolved independently in several arthropod lineages that can live far away from water,^[13] for example the tubules of insects and arachnids develop from completely different parts of the embryo.^[8] However a few primitive spiders, the sub-order Mesothelae and infra-order Mygalomorphae, retain the ancestral arthropod nephridia ("little kidneys"),^[7] which use large amounts of water to excrete nitrogenous waste products as ammonia.^[13]

Central nervous system

The basic arthropod central nervous system consists of a pair of nerve cords running below the gut, with paired ganglia as local control centers in all segments; a brain formed by fusion of the ganglia for the head segments ahead o f and behind the mouth, so that the esophagus is encircled by this conglomeration of ganglia.^[14] Except for the primitive Mesothelae, of which the Liphistiidae are the sole surviving family, spiders have the much more centralized nervous system that is typical of arachnids: all the ganglia of all segments behind the esophagus are fused, so that the cephalothorax is largely filled with nervous tissue and there are no ganglia in the abdomen;^[7][8][14] in the Mesothelae, the ganglia of the abdomen and the rear part of the cephalothorax remain unfused.^[12]

Sense organs

Eyes

Most spiders have four pairs of eyes on the top-front area of the cephalothorax, arranged in patterns that vary from one family to another.^[7] The pair at the front are of the type called pigment-cup ocelli ("little eyes"), which in most arthropods are only capable of detecting the direction from which light is coming, using the shadow cast by the walls of the cup. However the main eyes at the front of spiders' heads are pigment-cup ocelli that are capable of forming images.^[15][16] The other eyes are thought to be derived from the compound eyes of the ancestral chelicerates, but no longer have the separate facets typical of compound eyes. Unlike the main eyes, in many spiders these secondary eyes detect light reflected from a reflective tapetum lucidum, and wolf spiders can be spotted by torch light reflected from the tapeta. On the other hand ju mping spiders' secondary eyes have no tapeta.^[7] Jumping spiders' visual acuity exceeds by a factor of ten that of dragonflies, which have by far the best vision among insects; in fact the human eye is only about five times sharper than a jumping spider's. They achieve this by a telephoto-like series of lenses, a four-layer retina and the ability to swivel their eyes and integrate images from different stages in the scan. The downside is that the scanning and integrating processes are relatively slow.^[17]

Other senses

As with other arthropods, spiders' cuticles would block out information about the outside world, except that they are penetrated by many sensors or connections from sensors to the nervous system. In fact spider s and other arthropods have modified their cuticles into elaborate arrays of sensors. Various touch sensors, mostly bristles called setae, respond to different levels of force, from strong contact to very weak air currents. Chemical sensors provide equivalents of taste and smell, often by means of setae.^[15] Spiders also have in the joints of their limbs slit sensillae that detect forces and vibrations. In web-building spiders all these mechanical and chemical sensors are more important than the eyes, while the eyes are most important to spiders that hunt actively.^[7]

Like most arthropods, spiders lack balance and acceleration sensors and rely on their eyes to tell them which way is up. Arthropods' proprioceptors, sensors that report the for ce exerted by muscles and the degree of bending in the body and joints, are well understood. On the other hand little is known about what other internal sensors spiders or other arthropods may have.^[15]

Locomotion

Although all arthropods use muscles attached to the inside of the exoskeleton to flex their limbs, spiders and a few other groups still use hydraulic pressure to extend them, a system inherited from their pre-arthropod ancestors.^[18] As a result a spider with a punctured cephalothorax cannot extend its legs, and the legs of dead spiders curl up.^[7] Spiders can generate pressures up to eight times their resting level to extend their legs,^[19] and jumping spiders can jump up to 50 times their own length by suddenly increasing the blood pressure in the third or fourth pair of legs.^[7]

Most spiders that hunt actively, rather than relying on webs, have dense tufts of fine hairs between the paired claws at the tips of their legs. These tufts, known as scopulae, consist of bristles whose ends are split into as many as 1,000 branches, and enable spiders with scopulae to walk up vertical glass and upside down on ceilings. It appears that scopulae get their grip from contact with extremely thin layers of water on surfaces.^[7] Spiders, like most other arachnids, keep at least four legs on the surface while walking or running.^[20]

Silk production

The abdomen has no appendages except those that have been modified to form one to four (usually three) pairs of short, movable spinnerets, which emit silk. Each spinneret has many spigots, each of which is connected to one silk gland. There are at least six types of silk gland, each producing a different type of silk.^[7]

Silk is mainly composed of a protein very similar to that used in insect silk. It is initially a liquid, and hardens not by exposure to air but as a result of being drawn out, which changes the internal structure of the protein.^[21] It is similar in tensile strength to nylon and biological materials such as chitin, collagen and cellulose, but is much more elastic, in other words it can stretch much further before breaking or losing shape.^[7]

Some spiders have a cribellum, a modified spinneret with up to 40,000 spigots, each of which produces a single very fine fiber. The fibers are pulled out by the calamistrum, a comb-like set of bristles on the jointed tip of the cribellum, and combined into a composite woolly thread that is very effective in snagging the bristles of insects. The earliest spiders had crib ella, which produced the first silk capable of capturing insects, before spiders developed silk coated with sticky droplets. However most modern groups of spiders have lost the cribellum.^[7]

Tarantulas also have silk glands in their feet.^[22]

Even species that do not build webs to catch prey use silk in several ways: as wrappers for sperm and for fertilized eggs; as a "safety rope"; for nest-building; and as "parachutes" by the young of some species.^[7]

Reproduction and life cycle

Spiders reproduce sexually and fertilization is internal but indirect, in other words the sperm is not inserted into the female's body by the male's genitals but by an intermediate stage. Unlike many land-living arthropods,^[23] male spiders do not produce ready-made spermatophores (packages of sperm) but spin small sperm webs on to which they ejaculate and then transfer the sperm to syringe-like structures on the tips of their pedipalps. When a male detects signs of a female nearby he checks whether she is of the same species and whether she is rea dy to mate; for example in species that produce webs or "safety ropes", the male can identify the species and sex of these objects by "smell".^[7]

Spiders generally use elaborate courtship rituals to prevent the large females from eating the small males before fertilization, except where the male is so much smaller that he is not worth eating. In web-weaving species precise patterns of vibrations in the web are a major part of the rituals, while patterns of touches on the female's body are important in many spiders that hunt actively, and may "hypnotize" the female. Gestures and dances by the male are important for jumping spiders, which have excellent eyesight. If courtship is successful, the male injects his sperm from the pedipalps into the female's genital opening, known as the epigyne, on the underside of her abdomen. Female's reproductive tracts vary from simple tubes to systems that include seminal receptacles in which females store sperm and release it when they are ready.^[7]

Males of the genus Tidarren amputate one of their palps before maturation and enter adult life with one palp only. The palps are 20% of male's body mass in this species, and detaching one of the two improves mobility. In the Yemeni species Tidarren argo, the remaining palp is then torn off by the female. The separated palp remains attached to the female's epigynum for about four hours and apparently continues to function independently. In the meantime the female feeds on the palpless male.^[24] In over 60% of cases the female of the Australian redback spider kills and eats the male after it inserts its second palp into the female's genital opening; in fact the males co-operate by trying to impale themselves on the females' fangs. Observation shows that most male redbacks never get an opportunity to mate, and the "lucky" ones increase the likely number of offspring by ensuring that the females are well-fed.^[25] However males of most species survive a few matings, limited mainly by their short life spans. Some even live for a while in their mates' webs.^[26]

Females lay up to 3,000 eggs in one or more silk egg sacs,^[7] which maintain a fairly constant humidity level.^[26] In some species the females die afterwards, but females of other species protect the sacs by attaching them to their webs, hiding them in nests, carrying them in the chelicerae or attaching them to the spinnerets and dragging them along.^[7]

Baby spiders pass all their larval stages inside the egg and hatch as spiderlings, very small and sexually immature but similar in shape to adults. Some spiders care for their young, for example a wolf spider's brood cling to rough bristles on the mother's back,^[7] and females of some species respond to the "begging" behaviour of their young by giving them their prey, provided it is no longer struggling, or even regurgitate food.^[26]

Like other arthropods, spiders have to molt to grow as their cuticle ("skin") cannot stretch.^[27] In some species males mate with newly molted females, which are too weak to be dangerous to the males.^[26] Most spiders live for only one to two years, although some tarantulas can live in captivity for over 20 years.^[7][28]

Size

Spiders occur in a large range of sizes. The smallest, Patu digua from Colombia, are less than 0.37 mm (0.015 in) in body length. The largest and heaviest spiders occur among tarantulas, which can have body lengths up to 90 mm (3.5 in) and leg spans up to 250 mm (10 in).^[29]

Coloration

Only three classes of pigment (ommochromes, bilins and guanine) have been identified in spiders, although other pigments have been detected but not yet characterized. Melanins, carotenoids and pterins, very common in other animals, are apparently absent. In some species the exocuticle of the legs and prosoma is modified by a tanning process, resulting in brown coloration.^[30] Bilins are found, for examp le, in Micrommata virescens, resulting in its green color. Guanine is responsible for the white markings of the European garden spider Araneus diadematus. It is in many species accumulated in specialized cells called guanocytes. In genera such as Tetragnatha, Leucauge, Argyrodes or Theridiosoma, guanine creates their silvery appearance. While guanine is originally an end-product of protein metabolism, its excretion can be blocked in spiders, leading to an increase in its storage.^[30] Structural colors occur in some species, which are the result of the diffraction, scattering or interference of light, for example by modified setae or scales. The white prosoma of Argiope results from hairs reflecting the light, Lycosa and Josa both have areas of modified cuticle that act as light reflectors.^[30]

Ecology and behavior

Non-predatory feeding

Although spiders are generally regarded as predatory, the jumping spider Bagheera kiplingi gets over 90% of its food from fairly solid plant material produced by acacias as part of a mutually beneficial relationship with a species of ant.^[31]

Juveniles of some spiders in the families Anyphaenidae, Corinnidae, Clubionidae, Thomisidae and Salticidae feed on plant nectar. Laboratory studies show that they do so deliberately and over extended periods, and periodically clean themselves while feeding. These spiders also prefer sugar solutions to plain water, which indicates that they are seeking nutrients. Since many spiders are nocturnal , the extent of nectar consumption by spiders may have been under-estimated. Nectar contains amino acids, lipids, vitamins and minerals in addition to sugars, and studies have shown that other spider species live longer when nectar is available. Feeding on nectar avoids the risks of struggles with prey, and the costs of producing venom and digestive enzymes.^[32]

Various species are known to feed on dead arthropods (scavenging), web silk, and their own shed exoskeletons. Pollen caught in webs may also be eaten, and studies have shown that young spiders have a better chance of survival if they have the opportunity to eat pollen. In captivity, several spider species are also known to feed on bananas, marmalade, milk, egg yolk and sausages.^[32]

Methods of capturing prey

The best-known method of prey capture is by means of sticky webs. Varying placement of webs allows different species of spider to trap different insects in the same area, for example flat horizontal webs trap insects that fly up from vegetation underneath while flat vertical webs trap insects in horizontal flight. Web-building spiders have poor vision, but are extremely sensitive to vibrations.^[7]

Females of the water spider < i>Argyroneta aquatica build underwater "diving bell" webs which they fill with air and use for digesting prey, molting, mating and raising offspring. They live almost entirely within the bells, darting out to catch prey animals that touch the bell or the threads that anchor it.^[33] A few spiders use the surfaces of lakes and ponds as "webs", detecting trapped insects by the vibrations that these cause while struggling.^[7]

Net-casting spiders weave only small webs but then manipulate them to trap prey. Those of the genus Hyptiotes and the family Theridiosomatidae stretch their webs and then release them when prey strike them, but do not actively move their webs. Those of the family Deinopidae weave even smaller webs, hold them outstretched between their first two pairs of legs, and lunge and push the webs as much as twice their own body length to trap prey, and this move may increase the webs' area by a factor of up to ten. Experiments have shown that Deinopis spinosus has two different techniques for trapping prey: backwards strikes to catch flying insects, whose vibrations it detects; and forward strikes to catch ground-walking prey that it sees. These two techniques have also been observed in other deinopids. Walking insects form most of the prey of most deinopids, but one population of Deinopis subrufa appears to live mainly on tipulid flies that they catch with the backwards strike.^[34]

Mature female bolas spiders of the genus Mastophora build "webs" that consist of only a single "trapeze line", which they patrol. They also construct a bolas made of a single thread, tipped with a large ball of very wet sticky silk. They emit chemicals that resemble the pheromones of moths, and then swing the bolas at the moths. Although they miss on about 50% of strikes, they catch about the same weight of insects per night as web-weaving spiders of similar size. The spiders eat the bolas if they have not made a kill in about 30 minutes, rest for a while, and then make new bolas.^[35][36] Juveniles and adult males are much smaller and do not make bolas. Instead they release different pheromones that attract moth flies, and catch them with their front pairs of legs.^[37]

The primitive Liphistiidae, the "trapdoor spiders" (family Ctenizidae) and many tarantulas are ambush predators that lurk in burrows, often closed by trapdoors and often surrounded by networks of silk threads that alert these spiders to the presence of prey.^[12] Other ambush predators do without such aids, including many crab spiders,^[7] and a few species that prey on bees, which see ultraviolet, can adjust their ultraviolet reflectance to match the flowers in which they are lurking.^[30] Wolf spiders, jumping spiders, fishing spiders and some crab spiders capture prey by chasing it, an d rely mainly on vision to locate prey.^[7]

Some jumping spiders of the genus Portia hunt other spiders in ways that seem intelligent,^[17] outflanking their victims or luring them from their webs. Laboratory studies show that Portia's instinctive tactics are only starting points for a trial-and-error approach from which these spiders learn very quickly how to overcome new prey species.^[38] However they seem to be relatively slow "thinkers", which is not surprising, as their brains are vastly smaller than those of mammalian predators.^[17]

Ant-mimi cking spiders face several challenges: they generally develop slimmer abdomens and false "waists" in the cephalothorax to mimic the three distinct regions (tagmata) of an ant's body; they wave the first pair of legs in form to their heads to mimic antennae, which spiders lack, and to conceal the fact that they have eight legs rather than six; they develop large color patches round one pair of eyes to disguise the fact that they generally have eight simple eyes, while ants have two compound eyes; they cover their bodies with reflective hairs to resemble the shiny bodies of ants. In some spider species, males and females mimic different ant species, as female spiders are usually much larger than males. Ant-mimicking spiders also modify their behavior to resemble that of the target species of ant; for example, many adopt a zig-zag pattern of movement, ant-mimicking jumping spiders avoid jumping, and spiders of the genus Synemosyna walk on the outer edges of leaves in the same way as Pseudomyrmex. A nt-mimicry in many spiders and other arthropods may be for protection from predators that hunt by sight, including birds, lizards and spiders. However, several ant-mimicking spiders prey either on ants or on the ants' "livestock", such as aphids. When at rest, the ant-mimicking crab spider Amyciaea does not closely resemble Oecophylla, but while hunting it imitates the behavior of a dying ant to attract worker ants. After a kill, some ant-mimicking spiders hold their victims between themselves and large groups of ants to avoid being attacked.^[39]

Defense

There is str ong evidence that spiders' coloration is camouflage that helps them to evade their major predators, birds and parasitic wasps, both of which have good color vision. Many spider species are colored so as to merge with their most common backgrounds, and some have disruptive coloration, stripes and blotches that break up their outlines. In a few species, such as the Hawaiian happy-face spider, Theridion grallator, several coloration schemes are present in a ratio that appears to remain constant, and this may make it more difficult for predators to recognize the species. Most spiders are insufficiently dangerous or unpleasant-tasting for warning coloration to offer much benefit. However a few species with powerful venoms, large jaws or irritant hairs have patches of warning colors, and some actively display these colors when threatened.^[30][40]

Many of the family Theraphosidae, which includes tarantulas and baboon spiders, have urticating hairs on their abdomens and use their legs to flick them at attackers. These hairs are fine setae (bristles) with fragile bases and a row of barbs on the tip. The barbs cause intense irritation but there is no evidence that they carry any kind of venom.^[41] A few defend themselves against wasps by including networks of very robust threads in their webs, giving the spider time to flee while the wasps are struggling with the obstacles.^[42] The golden wheeling spider, Carparachne aureoflava, of the Namibian desert escapes parasitic wasps by flipping onto its side and cartwheeling down sand dunes.^[43]

Social spiders

A few species of spiders that build webs live together in large colonies and show social behavior, although not as complex as in social insects. Anelosimus eximius (in the family Theridiidae) can form colonies of up to 50,000 individuals.^[44] The genus Anelosimus has a strong tendency towards sociality: all known American species are social, and species in Madagascar are at least somewhat social.^[45] Members of other species in the same family but several different genera have independently developed social behavior. For example, although Theridion nigroannulatum belongs to a genus with no other social species, T. nigroannulatum build colonies that may contain several thousand individuals that co-operate in prey capture and share food.^[46] Other communal spiders include several Philoponella species (family Uloboridae), Agelena consociata (family Agelenidae) and Mallos gregalis (family Dictynidae).^[47] Social predatory spiders need to defend their prey against kleptoparasites ("thieves"), and larger colonies are more successful in this.^[48] The herbivorous spider Bagheera kiplingi lives in small colonies which help to protect eggs and spiderlings.^[31] Even widow spiders (genus Latrodectus), which are notoriously aggressive and cannibalistic, have formed small colonies in captivity, sharing webs and feeding together.^[49]

Web types

There is no consistent relationship between the classification of spiders and the types of web they build: species in the same genera may build very similar or significantly different webs. Nor is there much correspondence between spiders' classification and the chemical composition of their silks. Convergent evolution in web construction, in other words use of similar techniques by remotely related species, is rampant. Non-orb web designs and the spinning behaviors that produce the m have received very little attention from arachnologists, despite the fact that the majority of spiders build non-orb webs. The basic radial-then-spiral sequence visible in orb webs and the sense of direction required to build them may have been inherited from the common ancestors of most spider groups.^[50] It used to be thought that the sticky orb web was an evolutionary innovation resulting in the diversification of the Orbiculariae. Now, however, it appears that non-orb spiders are a sub-group that evolved from orb-web spiders, and non-orb spiders have over 40% more species and are four times as abundant as orb-web spiders. Their greater success may be because sphecid wasps, which are often the dominant predators on spiders, much prefer to attack spiders that have flat webs.^[51]

Orb webs

About half the potential prey that hit orb webs escape. A web has to perform three functions: intercepting the prey (intersection); absorbing its momentum without breaking (stopping); and trapping the prey by entangling it or sticking to it (retention). No single design is best for all prey. For example: wider spacing of lines will increase the web's area and hence its ability to intercept prey, but reduce its stopping power and retention; closer spacing, larger sticky droplets and thicker lines would improve retention, but would ma ke it easier for potential prey to see and avoid the web, at least during the day. However there are no consistent differences between orb webs built for use during the day and those built for use at night. In fact there is no simple relationship between orb web design features and the prey they capture, as each orb-weaving species takes a wide range of prey.^[50]

The hubs of orb webs, where the spiders lurk, are usually above the center as the spiders can move downwards faster than upwards. If there is an obvious direction in which the spider can retreat to avoid its own predators, the hub is usually offset towards that direction.^[50]

Horizontal orb webs are fairly common , despite being less effective at intercepting and retaining prey and more vulnerable to damage by rain and falling debris. Various researchers have suggested that horizontal webs offer compensating advantages, such as: reduced vulnerability to wind damage; reduced visibility to prey flying upwards, because of the back-lighting from the sky; enabling oscillations to catch insects in slow horizontal flight. However there is no single explanation for the common use of horizontal orb webs.^[50]

Spiders often attach highly visible silk bands called decorations or stabilimenta to their webs. Field research suggests that webs with more decorative bands captured more prey per hour.^[52] However a laboratory study showed that spiders reduce the building of these decorations if they sense the presence of predators.^[53]

There are several unusual variants of orb web, many of them convergently evolved, including: attachment of lines to the surface of water, possibly to trap insects in or on the surface; webs with twigs through their centers, possibly to hide the spiders from predators; "ladder-like" webs that appear most effective in catching moths. However the significance of many variations is unclear.^[50]

In 1973, Skylab 3 took two orb-web spiders into space to test their web-spinning capabilities in zero gravity. At first both produced rather sloppy webs, but they adapted quickly.^[54]

Tangleweb spiders (cobweb spiders)

Members of the family Theridiidae weave irregular, tangled, three-dimensional webs, popularly known as cobwebs.There seems to be an evolutionary trend towards a reduction in the amount of sticky silk used, leading to its total absence in some species. The construction of cobwebs is less stereotyped than that of orb-webs, and may take several days.^[51]

Other types of webs

The Linyphiidae generally make horizontal but uneven sheets, with tangles of stopping threads above. Insects that hit the stopping threads fall on to the sheet or are shaken on to it by the spider, and are held by sticky threads on the sheet until the spider can attack from below.^[55]

Evolution

Fossil record

Although the fossil record of spiders is considered poor,^[56] almost 1000 species have been described from fossils.^[57] Because spid ers' bodies are quite soft, the vast majority of fossil spiders have been found preserved in amber.^[57] The oldest known amber that contains fossil arthropods dates from 130 million years ago in the Early Cretaceous period. In addition to preserving spiders' anatomy in very fine detail, pieces of amber show spiders mating, killing prey, producing silk and possibly caring for their young. In a few cases amber has preserved spiders' egg sacs and webs, occasionally with prey attached;^[58] the oldest fossil web found so far is 100 million years old.^[59] Earlier spider fossils come from a few lagerst?tten, places where conditions were exceptionally suited to preserving fairly soft tissues.^[58]

The oldest known arachnid is the trigonotarbid Palaeotarbus jerami, from about 420 million years ago in the Silurian period, and had a triangular cephalothorax and segmented abdomen, as well as eight legs and a pair of pedipalps.^[60] Attercopus fimbriunguis, from 386 million years ago in the Devonian period, bears the earliest known silk-producing spigots, and was therefore hailed as a spider.^[61] However these spigots may have been mounted on the underside of the abdomen rather than on spinnerets, which are modified appendages and whose mobility is important in the building of webs. Hence Attercopus and the similar Permian arachnid Permarachne may not have been true spiders, and probably used silk for lining nests or producing egg-cases rather than for building webs.^[62] The largest known fossil spider as of 2011 is the araneid Nephila jurassica, from about 165 million years ago, recorded from Daohuogo, Inner Mongolia in China.^[63]

Several Carboniferous spiders were members of the Mesothelae, a primitive group now represented only by the Liphistiida e.^[61] The mesothelid Paleothele montceauensis, from the Late Carboniferous over 299 million years ago, had five spinnerets.^[64] Although the Permian period 299 to 251 million years ago saw rapid diversification of flying insects, there are very few fossil spiders from this period.^[61]

The main groups of modern spiders, Mygalomorphae and Araneomorphae, first appear in the Triassic well before 200 million years ago. Some Triassic mygalomorphs appear to be members of the family Hexathelidae, whose modern members include the notorious Sydney funnel-web spider, and their s pinnerets appear adapted for building funnel-shaped webs to catch jumping insects. Araneomorphae account for the great majority of modern spiders, including those that weave the familiar orb-shaped webs. The Jurassic and Cretaceous periods provide a large number of fossil spiders, including representatives of many modern families.^[61]

Family tree

It is now agreed that spiders (Araneae) are monophyletic (i.e., members of a group of organisms which form a clade, consisting of a last common ancestor and all of its descendants).^[66] There has been debate about what their closest evolutionary relatives are, and how all of these evolved from the ancestral chelicerates, which were marine animals. The cladogram on the right is based on J.W. Shultz' analysis (2007). Other views include proposals that: scorpions are more closely related to the extinct marine scorpion-like eurypterids than to spiders; spiders and Amblypygi are a monophyletic group. The appearance of several multi-way branchings in the tree on the right shows that there are still uncertainties about relationships between the groups involved.^[66]

Arachnids lack some features of other chelicerates, including backward-pointing mouths and gnathobases ("jaw bas es") at the bases of their legs;^[66] both of these features are part of the ancestral arthropod feeding system.^[67] Instead they have mouths that point forwards and downwards, and all have some means of breathing air.^[66] Spiders (Araneae) are distinguished from other arachnid groups by several characteristics, including spinnerets and, in males, pedipalps that are specially adapted for sperm transfer.^[68]

Taxonomy

Spiders are divided into two sub-orders, Mesothelae and Opisthothelae, of which the latter contains two infra-orders, Mygalomorphae and Araneomorphae. Over 40,000 living species of spiders (order Araneae) have been identified and are currently grouped into about 110 families and about 3,700 genera by arachnologists.^[2][68]

Mesothelae

The only living members of the primitive Mesothelae are the family Liphistiidae, found only in Southeast Asia, China, and Japan.^[68] Most of the Liphistiidae construct silk-lined burrows with thin trapdoors, although some species of the genus Liphistius build camouflaged silk tubes with a second trapdoor as an emergency exit. Members of the genus Liphistius run silk "tripwires" outwards from their tunnels to help them detect approaching prey, while those of genus Heptathela do not and instead rely on their built-in vibration sensors.^[71] Spiders of the genus Heptathela have no venom glands al though they do have venom gland outlets on the fang tip.^[72]

The extinct families Arthrolycosidae, found in Carboniferous and Permian rocks, and Arthromygalidae, so far found only in Carboniferous rocks, have been classified as members of the Mesothelae.^[73]

Mygalomorphae

Taxonomy

The Order Araneae is further organized into finer groupings including:

• Suborder (3): Labidognatha · Mesothelae · Opisthothelae
• Infraorder (2): Araneomorphae · Mygalomorphae
• Family (113): Actinopodidae · Agelenidae · Amaurobiidae · Ammoxenidae · Amphinectidae · Anapidae · Antrodiaetidae · Anyphaenidae · Araneidae · Archaeidae · Asauridae · Atypidae · Austrochilidae · Barychelidae · Caponiidae · Chummidae · Cithaeronidae · Clubionidae · Corinnidae · Cryptothelidae · Ctenidae &m iddot; Ctenizidae · Cyatholipidae · Cybaeidae · Cycloctenidae · Cyrtaucheniidae · Deinopidae · Desidae · Dictynidae · Diguetidae · Dipluridae · Drymusidae · Dysderidae · Eresidae · Filistatidae · Gallieniellidae · Gnaphosidae · Gradungulidae · Hahniidae · Halidae · Hersiliidae · Hexathelidae · Holarchaeidae · Homalonychidae · Huttoniidae · Hypochilidae · Idiopidae · Juraraneidae · Lamponidae · Leptonetidae · Linyphiidae · Liocranidae · Liphistiidae · Lycosidae · Malkaridae · Mecicobothriidae · Mecysmaucheniidae · Micropholcommatidae · Microstigmatidae · Migidae · Mimetidae · Miturgidae · Mysmenidae · Nemesiidae · Neolanidae · Nephilidae · Nesticidae · Nicodamidae · Ochyroceratidae · Oecobiidae · Oonopidae · Orsolobidae · Oxyopidae · Palpimanidae · Pararchaeidae · Paratropididae · Periegopidae · Philodromidae · Pholcidae · Phyxelididae · Pimoidae · Pisauridae · Plectreuridae · Prodidomidae · Psechridae · Salticidae · Scytodidae · Segestriidae · Selenopidae · Senoculidae · Sicariidae · Sparassidae · Stenochilidae · Stiphidiidae · Symphytognathidae · Synaphridae · Synotaxidae · Telemidae · Tengellidae · Tetrablemmidae · Tetragnathidae · Theraphosidae · Theridiidae · Theridiosomatidae · Thomisidae &mi ddot; Titanoecidae · Trechaleidae · Trochanteriidae · Uloboridae · Zodariidae · Zoridae · Zorocratidae · Zoropsidae
• Species: ZipcodeZoo has pages for 56,431 species and subspecies in the Order Araneae.

Families

Actinopodidae

The spider family Actinopodidae is a family of mygalomorph spiders found in Australia, South America, and Central America. It includes the Australian genus Missulena, known as the mouse spiders, which are quite venomous. [more]

Agelenidae

The araneomorph funnel-web spiders of the family Agelenidae include the common grass spiders of the genus Agelenopsis, as well as the purportedly venomous European hobo spider, Tegenaria agrestis, which has been introduced into the Pacific Northwest of the United States. Note: The araneomorph funnel-web spider should not to be confused with the funnel-web tarantula and the venomous funnel-web tarantula, both of which are members of the suborder Mygalomorphae. The venomous funnel-web tarantulas include the infamous Sydney funnel-web spider. [more]

Amaurobiidae

The Amaurobiidae are three-clawed cribellate or ecribellate spiders found in most parts of the world and difficult to distinguish from related spiders in other families, especially Agelenidae, Desidae and Amphinectidae. Their intra- and interfamilial relationships are contentious. In Spider Families of the World 2007 they were represented by 69 genera and about 640 species in 5 subfamilies. [more]

Ammoxenidae

The Ammoxenidae are a small spider family with 18 species in four genera. [more]

Amphinectidae

The Amphinectidae are a spider family with about 180 described species in 35 genera. [more]

Anapidae

The Anapidae are a family of rather small spiders with 145 described species in 35 genera. Most species are less than 2 mm long. [more]

Antrodiaetidae

The folding trapdoor spiders (Antrodiaetidae) are a small spider family with about 30 species in three genera. They are related to the Atypidae (atypical tarantulas). [more]

Anyphaenidae

The anyphaenid sac spiders (family Anyphaenidae) are distinguished from the sac spiders and other spiders by having the abdominal spiracle placed one third to one half of the way anterior to the spinnerets toward the epigastric furrow on the underside of the abdomen. In most spiders the spiracle is just anterior to the spinnerets. Like clubionids, anyphaenids have eight eyes arranged in two rows, conical anterior spinnerets and are wandering predators that built silken retreats, or sacs, usually on plant terminals, between leaves, under bark or under rocks. There are more than 500 species in over 50 genera worldwide. [more]

Araneidae

The "typical" orb-weaver spiders (family Araneidae) are the most common group of builders of spiral wheel-shaped webs often found in gardens, fields and forests. Their common name is taken from the round shape of this typical web, and the taxon was formerly also referred to as the Orbiculariae. [more]

Archaeidae

The Archaeidae are a spider family with 25 described species in three genera. [more]

Asauridae

[more]

Atypidae

The atypical tarantulas or purseweb spiders (family Atypidae) consist of only three genera. Purseweb spiders are accomplished ambush predators that spend most of their time in a sock-like, silken retreat on the ground from where they kill their prey. [more]

Austrochilidae

The Austrochilidae are a small spider family with nine species in three genera. [more]

Barychelidae

The Brushed trapdoor spiders (family Barychelidae) are a spider family with about 300 species in 44 general. This family is the only family in superfamily Barycheloidea. [more]

Caponiidae

Spiders of the ecribellate haplogyne family Caponiidae are unusual in that most species have only two eyes, which is unheard of in other spiders. Other species have four, six or eight eyes. Even in a single species, sometimes the number of eyes changes from spiderling to adult. [more]

Chummidae

The Chummidae are a tiny spider family with only two described species in one genus. Both were first described in 2001. Both species are known from males and females. [more]

Cithaeronidae

The Cithaeronidae are a small spider family with only six species in two genera. [more]

Clubionidae

The sac spiders of the family Clubionidae have a very confusing taxonomic history. Once this family was a large catch-all taxon for a disparate collection of spiders, similar only in that they had eight eyes arranged in two rows, conical anterior spinnerets that touched and were wandering predators that built silken retreats, or sacs, usually on plant terminals, between leaves, under bark or under rocks. These are now recognized to include several families, some of which are more closely related to the three-clawed spiders, like lynx and wolf spiders, than to true "clubionoids." [more]

Corinnidae

The corinnid sac spiders (family Corinnidae), like the other clubionoid families, have a very confusing taxonomic history. Once this family was a part of the large catch-all taxon Clubionidae, now a shadow of its former self. The clubionoids are apparently similar only in that they have eight eyes arranged in two rows, conical anterior spinnerets that touch and are generally wandering predators that build silken retreats, or sacs, usually on plant terminals, between leaves, under bark or under rocks. [more]

Cryptothelidae

[more]

Ctenidae

The wandering spiders is a term used to refer to the spider family Ctenidae. Previously, the term referred only to the genus Phoneutria but now usually refers to the entire family Ctenidae. The members of the genus Phoneutria are highly aggressive and venomous nocturnal hunters, and are the only wandering spiders known to pose a serious danger to humans. However, the venom of some other members of this family is very poorly known, meaning that all larger Ctenids should be treated with caution. Ctenids have a distinctive longitudinal groove on the top-rear of their oval carapace (some other spiders have a similar groove; e.g., Amaurobiidae). Venom from wandering spider injected in human body can lead to death within 2-12 hours. The venom induces release of nitric oxide which acts as a dilating agent and arteries and veins are dilated, it is then followed by increased blood flow in penis and results in a long duration penal erection. Finally the victim dies by a heart stroke. [more]

Ctenizidae

Trapdoor spiders (superfamily Ctenizoidea, family Ctenizidae) are medium-sized mygalomorph spiders that construct burrows with a cork-like trapdoor made of soil, vegetation and silk. Some similar species are also called trapdoor spiders, such as the Liphistiidae, Barychelidae, Cyrtaucheniidae and some Idiopidae and Nemesiidae. Some Conothele species do not build a burrow, but construct a silken tube with trap-door in bark crevices. [more]

Cyatholipidae

The Cyatholipidae are a spider family with 58 described species in 23 genera. [more]

Cybaeidae

Cybaeidae is a family of spiders comprising twelve genera. [more]

Cycloctenidae

Cycloctenidae is a spider family with 36 described species in 5 genera. The genera (5 spp.), Toxopsiella (12 spp.) and Uzakia (1 sp.) are all endemic to New Zealand, Cycloctenus is found in both Australia (7 spp.) and New Zealand (10 spp.), while Galliena (1 sp.) is endemic to Java. The placements of Galliena, Plectophanes and Uzakia in Cycloctenidae are tentative only. [more]

Cyrtaucheniidae

The wafer trapdoor spiders (superfamily Cyrtauchenioidea, family Cyrtaucheniidae) are a widespread family of spiders that lack the thorn-like spines on tarsi and metatarsi I and II (the two outermost leg segments) found in true trapdoor spiders (Ctenizidae).
[more]

Deinopidae

The spider family Deinopidae consists of stick-like elongate spiders that build unusual webs that they suspend between the front legs. When prey approaches, the spider will stretch the net to two or three times its relaxed size and propel itself onto the prey, entangling it in the web. Because of this, they are also called net-casting spiders. Their excellent night-vision adapted anterior median eyes allow them to cast this net over potential prey items. These eyes are so large in comparison to the other six eyes that the spider seems to have only two eyes. [more]

Desidae

The intertidal spiders (family Desidae) live in a very unusual location ? between the tides. Once thought to be limited to the Southern Hemisphere, members of this family in the genus were discovered in northern Sonora and the Florida Keys during the last half of the 20th Century. The family has been reevaluated in recent years and now includes inland genera and species as well. Members of the genus Paratheuma commonly live in barnacle shells, which they seal up with silk. This allows them to maintain an air bubble during high tide. These intertidal spiders feed on various small arthropods that live in the intertidal zone. [more]

Dictynidae

Dictynidae is a family of cribellate (hackled band-producing) spiders. Most spiders in this family build irregular webs close to or directly on the ground. Typically they create a tangle of silken fibers among several branches or stems of one plant. [more]

Diguetidae

The coneweb spiders of the family Diguetidae are six-eyed haplogyne (lacking hardened female genitalia, or epigyne) spiders that live in tangled space webs. They fashion a cone-like central retreat in which they hide and lay eggs. The family is small (three genera and only 15 species) and is confined to the New World, where it is usually found in deserts. Members of the genus Diguetia usually build their webs in shrubs or between cactus pads. Although they have the same eye arrangement as the venomous recluse spiders (family Sicariidae), none of these genera are known to be harmful to humans. [more]

Dipluridae

Funnel-web tarantulas (super-family Dipluroidea, family Dipluridae), are a group of spiders in the infraorder Mygalomorphae, that have two pairs of booklungs, and chelicerae (fangs) that move up and down in a stabbing motion. A number of genera, including the Sydney funnel-web spider (Atrax robustus), used to be classified in this family but have now been moved to Hexathelidae. [more]

Drymusidae

The Drymusidae are a small spider family with ten species in one genus. They are also called false violin spiders or leaf-litter spiders. They resemble the violin spider or recluse spider (genus Loxosceles, Sicariidae), but other than these build a web[1]. Also unlike Loxosceles, which are highly venomous to man, spiders in Drymusidae are not believed to be harmful to humans. [more]

Dysderidae

The family Dysderidae (woodlouse hunters, sowbug-eating spiders or cell spiders) are araneomorph spiders found primarily in Eurasia, although extending into North Africa, with very few species occurring in South America, and one (Dysdera crocata) introduced into many regions of the world. [more]

Eresidae

The velvet spiders (family Eresidae) are a small group (about 100 species in 10 genera) of almost totally Old World spiders (exception: a few species are known from Brazil). The characteristics of this family of spiders are that they are entelegyne (have a genital plate in the female), eight-eyed araneomorph spiders that build unkempt webs. With the exception of Wajane, they are cribellate (use wooly silk). Some species are nearly eusocial, lacking only a specialized caste system and a queen. They cooperate in brood rearing, unlike almost most other spiders except for some African agelenid spiders in the genus Agelena and a few others. [more]

Filistatidae

The crevice weaver spiders (super-family Filistatoidea, family Filistatidae) contain primitive cribellate. They are haplogyne weavers of funnel or tube webs. The family contains 17 genera and more than hundred described species worldwide. One of the most abundant members of this family in the Americas is the Southern house spider (Kukulcania hibernalis). Named after the fierce Meso-American god Kukulkan, the females are large (up to nearly 20 mm) dark-colored spiders and males are light brown, smaller (about 10 mm.), but more long-legged and with palpi that are held together in front of their carapaces like the horn of a unicorn. The males also have a darker streak on the center of the dorsal carapace that causes them to be often mistaken for brown recluse spiders. The tiny members of the genus Filistatinella are like miniature versions of Kukulcania. The nominate genus Filistata is Afro-Eurasian in distribution. In many older books the species from the Americas now placed in the genus Kukulcania are placed in Filistata. [more]

Gallieniellidae

The Gallieniellidae are a spider family with 48 species in ten genera. [more]

Gnaphosidae

Ground spiders (family Gnaphosidae) include nearly 2,000 described species in over 100 genera, distributed worldwide. This makes the family the seventh largest known. New species are still being discovered. They are closely related to Clubionidae. [more]

Gradungulidae

The Gradungulidae are a small spider family of Australia and New Zealand with 16 species in seven genera. They are medium to large three-clawed haplogyne spiders with two pairs of book-lungs (like Mygalomorphae). [more]

Hahniidae

The dwarf sheet spiders (family Hahniidae) are small spiders, their bodies are about 2 mm in length. They build extremely delicate webs in the form of a sheet, and unlike many spiders the web does not lead to a retreat. The silk used in these webs is so fine that they are difficult to spot unless they are coated with dew. They greatly favor locations near water or near moss, and are often found in leaf litter and detritus or on the leaves of shrubs and trees. [more]

Halidae

The Halidae are a tiny spider family with only three described species in two genera. As of 2006, this family is no longer considered valid; the two genera are instead grouped in the family Pisauridae. [more]

Hersiliidae

The tree trunk spiders are members of the tropical and semi-tropical Family Hersiliidae. There are about 150 species in this family. These spiders have two very prominent spinnerets that are almost as long as their abdomen. So they are also sometimes known as "two-tailed spiders." They range in size from about 10 mm (0.4 inch) to 18 mm (0.7 inch) long. Being very well camouflaged for life on the varicolored trunks of trees, they have an interesting way of capturing prey. Rather than making a web that captures prey directly, they lay a light coating of threads over an area of tree bark and wait hidden in plain sight for an insect to stray onto that patch. Once that occurs, they direct their spinnerets toward their prey and circle it; all the while casting silk on it. When the hapless insect has been thoroughly immobilized, they can bite it through its new shroud. [more]

Hexathelidae

The spider family Hexathelidae, the only family in the super-family Hexatheloidea, is one of two families (along with Dipluridae) of spiders known as funnel-webs. This order is sometimes incorrectly referred to (in unknown references) as the venomous funnel-web tarantulas, due to the inclusion of the Australian funnel-web spiders, including the Sydney funnel-web spider (Atrax robustus). Most specimens in Hexathelidae are not dangerous to humans. [more]

Holarchaeidae

The Holarchaeidae are a spider family with only two described species in one genus. [more]

Homalonychidae

The Homalonychidae are a very small spider family with three described species in one genus. [more]

Huttoniidae

Huttonia palpimanoides is a spider in its own family, Huttoniidae. [more]

Hypochilidae

The Lampshade spiders of the family Hypochilidae are among the most primitive of araneomorph spiders. There are two genera and twelve species currently recognized. Like mygalomorphs, hypochilids have two pairs of book lungs, but like araneomorphs they have intersecting fangs. These long-legged spiders build typical "lampshade" style webs under overhangs and in caves. In the United States the fauna is primarily associated with the Appalachian, Rocky and California Mountains. Ten of the known species are found in these ranges, all in the genus Hypochilus. The genus Ectatosticta is found in China. [more]

Idiopidae

Idiopidae (superfamily Idiopoidea are a mygalomorph spider family. They have a large body that often looks rather like a tarantula. [more]

Juraraneidae

[more]

Lamponidae

The Lamponidae are a spider family with about 200 described species in 23 genera. [more]

Leptonetidae

Leptonetidae is a family of relatively primitive haplogyne (lacking hardened external female genitalia) spiders, which includes 15 genera and nearly 200 species. The family is poorly known to anybody but specialists. Leptonetids are generally tiny, have six eyes arranged in a semicircle of four in front and two behind. Many live in caves or in leaf litter. They are found around the Mediterranean, and in Eurasia, Japan and the New World^[]. [more]

Linyphiidae

Linyphiidae is a family of spiders, including more than 4,300 described species in 578 genera worldwide. This makes Linyphiidae the second largest family of spiders after the Salticidae. New species are still being discovered throughout the world, and the family is poorly known. Because of the difficulty in identifying such tiny spiders, there are regular changes in taxonomy as species are combined or divided. [more]

Liocranidae

Liocranid sac spiders consist of about 160 species of wandering spiders in 30 or so genera. The best known are those in the Holarctic genus Agroeca. Various genera of rather obscure spiders are included in the family, which still lacks a diagnosis. Two species in the North American genus Neoanagraphis are found in often hyperarid conditions in the Mojave, Sonoran and Chihuahuan Deserts. The females apparently live in animal burrows and the males wander and are often caught in pitfall traps. [more]

Liphistiidae

The spider family Liphistiidae comprises 5 genera and 85 species from Southeast Asia, China, and Japan. They are among the most basal living spiders, belonging to the suborder Mesothelae. In Japan, the Kimura-gumo (Heptathela kimurai) is rather well-known. [more]

Lycosidae

Wolf spiders are members of the family Lycosidae, from the Ancient Greek word "" meaning "wolf". They are robust and agile hunters with good eyesight. They live mostly solitary lives and hunt alone. Some are opportunistic hunters pouncing upon prey as they find it or even chasing it over short distances. Some will wait for passing prey in or near the mouth of a burrow. [more]

Malkaridae

The Malkaridae are a small spider family with ten species in four genera. [more]

Mecicobothriidae

Dwarf tarantulas, also known as sheet funnel-web spiders are a type of spider from the family Mecicobothriidae. Dwarf tarantulas are one of several families of the sub-order Mygalomorphae; this larger group also includes the true tarantulas. [more]

Mecysmaucheniidae

The Mecysmaucheniidae are a spider family with 25 described species in seven genera. [more]

Micropholcommatidae

The Micropholcommatidae are a spider family with 33 described species in eight genera. Micropholcommatids are extremely small, with body lengths typically between 0.5 and 2 mm. They are usually found among leaf litter or moss. [more]

Microstigmatidae

The Microstigmatidae are a small spider family with fifteen described species in seven genera. They are small ground-dwelling and free-living spiders that make little use of silk. [more]

Migidae

The tree trapdoor spiders (Migidae) are a spider family with about 90 species in 10 genera. [more]

Mimetidae

The family Mimetidae, commonly called pirate spiders, are spiders which typically feed on other spiders. [more]

Miturgidae

The long-legged sac spiders (family Miturgidae) include nearly 400 species in about 30 genera worldwide. [more]

Mysmenidae

The Mysmenidae are a spider family with almost 100 described species in more than twenty genera. [more]

Nemesiidae

The Nemesiidae are a spider family of the infraorder Mygalomorphae, and the only member of the superfamily Nemesioidea. They were formerly considered part of the Dipluridae family. [more]

Neolanidae

The Amphinectidae are a spider family with about 180 described species in 35 genera. [more]

Nephilidae

[more]

Nesticidae

The scaffold web spiders of the family Nesticidae, are closely allied with the Theridiidae, or tangle web spiders. Like the Theridiidae these spiders have a comb of serrated bristles on the hind tarsi that are used to pull silk bands from the spinnerets. It contains nine genera and a little over 200 species, many of which are associated with caves or overhangs. The genus Nesticus is the type for the family and is found throughout the world. The related Eidmannella has speciated considerably in Texas caves and includes some extremely localized species that are considered threatened. One species, Eidmannella pallida, is found in caves and under overhangs, but also in agricultural fields and other habitats away from such restricted areas. The genus Carpathonesticus is found in central Eurasia. [more]

Nicodamidae

The Nicodamidae are a spider family with 29 species in nine genera. [more]

Ochyroceratidae

The Ochyroceratidae are a six-eyed spider family in the Leptonetoidea superfamily, with 154 described species in 14 genera. [more]

Oecobiidae

The spider family Oecobiidae (also called Disc web spiders) consists of about 100 species. [more]

Oonopidae

The spider family Oonopidae (Goblin spiders) includes about 459 species in about 65 genera worldwide. The type genus of the family is Oonops Keyserling, 1835. They are generally tiny (1-3 mm) haplogyne araneomorph spiders. Some have hardened plates (scuta) on their abdomens. Oonopids usually have six eyes, the anterior median eyes having been lost. However, four-eyed (Opopaea viamao), two-eyed (e.g. Coxapopha, Diblemma) and even completely eyeless species (e.g. Cousinea, the cave-dwelling Blanioonops) are also known. The family is permeated with unusual morphological traits, many of which are limited to males. Examples include heavily modified mouthparts (e.g. Coxapopha, Xyccarph), sternal pouches (sometimes alternatively called holsters; e.g. Grymeus) and extensions of the carapace (e.g. Ferchestina, Unicorn). The male pedipalps are also often highly modified. The genus Opopaea, for example, exhibits an expanded palpal patella while male Ischnothyreus are characterized by completely sclerotized, pitch-black pedipalps. Members of the genus Orchestina are believed to be able to jump, as both sexes have greatly enlarged femora on the fourth leg pair. Oonopidae are seldom seen by people as they are too small to be easily noticed. Generally, oonopid spiders are found in the leaf litter layer and under rocks but they also constitute a significant component of the spider fauna living in the canopy of tropical rain forests. Three blind Afrotropical genera (Anophthalmoonops, Caecoonops, Termitoonops) are exclusively found in termite nests. A few species, such as the pantropical Heteroonops spinimanus, are thought to be parthenogenetic as no males have so far been collected. [more]

Orsolobidae

The Orsolobidae are a six-eyed spider family with about 180 described species in 28 genera. They were separated from the Dysderidae. Several genera were transferred from the Oonopidae. [more]

Oxyopidae

Lynx Spiders are the members of the family Oxyopidae. They all are hunting spiders that spend their lives on plants, flowers and shrubs. At least one species has been identified as exhibiting social behaviour. [more]

Palpimanidae

The Palp-footed spiders (Palpimanidae) are a spider family with about 130 described species in 15 genera. Instead of the normal six, Palpimanidae have only two spinnerets. Their first legs are greatly enlarged.. All species produce ecribellate silk . Palpimanidae have six eyes, a red cephalothorax, very strong first legs, which are raised while moving. At least Palpimanus gibbulus lives in leaf litter or under stones in dry soils. [more]

Pararchaeidae

The Pararchaeidae are a spider family with 34 described species in seven genera. [more]

Paratropididae

The baldlegged spiders (Paratropididae) are a small spider family with eight species. They are related to tarantulas. [more]

Periegopidae

The spider family Periegopidae consists of only one genus Periegops, with two described species. Periegops had been long considered to be members of Sicariidae or Segestriidae until Raymond Forster evelated them to the family level in 1995. [more]

Philodromidae

Philodromidae is a family of spiders commonly known as philodromid crab spiders or running crab spiders. This family is superficially similar to the "true" crab spiders in the family Thomisidae. [more]

Pholcidae

Pholcidae, commonly known as cellar spiders, are a spider family in the suborder Araneomorphae. [more]

Phyxelididae

The Phyxelididae are a spider family with 54 described species in twelve genera. They are grouped with the Titanoecidae within the Titanoecoidea superfamily. [more]

Pimoidae

The Pimoidae spider family is a rather small group of 37 species in four genera. They are monophyletic, and probably closest related to the Linyphiidae. [more]

Pisauridae

Nursery web spiders are spiders of the family Pisauridae. They resemble wolf spiders (family Lycosidae), but they carry their egg sacs by means of their jaws and pedipalps (instead of attaching them to their spinnerets). When the eggs are about to hatch, a mother spider will build a nursery "tent", put her egg sac inside, and mount guard outside. The name nursery web spider is especially given to the European species Pisaura mirabilis, but the family also includes fishing spiders and raft spiders. [more]

Plectreuridae

'Plectreuridae, often called Plectreurid spiders, are a small spider family confined to the North American deserts and the island of Cuba. Only two living genera are known - the nominate genus and Kibramoa. In the past, the family was more widespread, with the Jurassic genus Eoplectreurys known from China, the Eocene Palaeoplectreurys baltica from Baltic amber and the Miocene Plectreurys pittfieldi from Dominican amber. [more]

Prodidomidae

The Prodidomidae are a spider family with about 300 species in 31 genera. They are sometimes called Long-Spinneret Ground Spiders. [more]

Psechridae

The Psechridae are a family of spiders with about two dozen species in two living genera. [more]

Salticidae

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. [more]

Scytodidae

Spitting spiders are members of the family Scytodidae. There are several genera, of which Scytodes is the best-known. Over 150 species of scytodids have been described worldwide. This means that the Scytodes is somewhat related to the family Sicariidae commonly known as Recluse spiders being that they are part of the same superfamily. [more]

Segestriidae

The tube-dwelling spiders (family Segestriidae) consist of two large and widespread genera (Segestria and Ariadna) and one monotypic genus (Gippsicola from Australia). The family is easily recognized because its members have six eyes (most spiders have eight) arranged in a semicircle and have the first three pairs of legs arranged forward (most spiders have only the first two pairs so arranged.) The leg structure appears to be an adaptation for living in silken tubes, which unlike those of the atypical tarantulas, may branch and are often built in tree bark fissures, as well as under stones. These are haplogyne primitive araneomorphs related to the Dysderidae. Both Segestria and Ariadna are known from North America, South America, Eurasia, Africa and New Zealand, while Ariadna is also known from Australia. This wide distribution attests to the ancient origin of this family. [more]

Selenopidae

The wall crab spiders (family Selenopidae), a member of a group of families collectively called crab spiders because of their laterigrade (sideways-moving) legs. This family consists of about 175 species in four genera, of which Selenops is the best known. The family is primarily tropical with the genus Anyphops confined to Sub-Saharan Africa and the genus Hovops confined to Madagascar. The spiders are very flat and are commonly found on walls or under rocks. They are quite agile and very difficult to capture. In addition their coloring makes them often quite difficult to see. Like almost all Entelegynae, they have eight eyes. At least one species of Garcorops, G. jadis is known only from subfossil copal. [more]

Senoculidae

They belong to the superfamily Lycosoidea. "Bark Hunter" is one common name used by researchers. Another name, "Monkey Ninja Spider," was proposed in December 2011 on YouTube, but is not currently an officially accepted name [more]

Sicariidae

Sicariidae is a family of six-eyed venomous spiders known for their necrotic bites. The members of this family are haplogyne by definition (instead of the most spiders that possess eight eyes). The family consists of two genera, Loxosceles and Sicarius, and contains about 120 species. Well known spiders in this family include the brown recluse spider and the assassin spider. [more]

Sparassidae

Sparassidae (formerly Heteropodidae) are a family of spiders known as Huntsman spiders because of their speed and mode of hunting. They also are called giant crab spiders, because of their size and appearance. Larger species sometimes are referred to as wood spiders, because of their preference for woody places (forest, mine shafts, woodpiles, wooden shacks), or clock spiders. In southern Africa they are known as rain spiders and lizard-eating spiders. Commonly they also are confused with baboon spiders, which are practically unrelated, being in a different infraorder, the Mygalomorphae. [more]

Stenochilidae

The Stenochilidae are a spider family with twelve described species in two genera. All species produce ecribellate silk (Griswold et al., 1999). [more]

Stiphidiidae

The Stiphidiidae are a spider family with 94 described species in 13 genera. They are generally of medium size (Stiphidium facetum is about 8 mm long) and build a horizontal tent-like web under rocks. Most species are speckled brown with long legs. [more]

Symphytognathidae

The Symphytognathidae are a spider family with 44 described species in six genera. [more]

Synaphridae

The Synaphridae are a spider family with twelve described species in three genera. [more]

Synotaxidae

The Synotaxidae are a spider family with 68 described species in 13 genera. [more]

Telemidae

The Telemidae are a six-eyed spider family with 57 described species in seven genera, see for details [more]

Tengellidae

The tengellid spiders (family Tengellidae) include eight genera and a little over 30 species worldwide. The family is confined to the New World, with two monotypic genera occurring in Madagascar and New Zealand, respectively. Like most spiders, they have eight eyes. The characters defining the family are technical and there are still some disagreements as to its size and placement within spider classification. According to Griswold (1993), the family is polyphyletic. This is another of the families removed from the catchall family Clubionidae over the last 20 or so years. [more]

Tetrablemmidae

The Tetrablemmidae are a spider family with 126 described species in 29 genera that occur throughout the world tropics. They are sometimes called armored spiders. [more]

Tetragnathidae

The long-jawed orb weavers or long jawed spiders (family Tetragnathidae) are elongated spiders with long legs and chelicerae. [more]

Theraphosidae

Tarantulas (as the term is used in North America) comprise a group of often hairy and often very large arachnids belonging to the family Theraphosidae, of which approximately 900 species have been identified. Although some members of the same suborder may also be called "tarantulas" in the common parlance, this article only describes members of Theraphosidae. [more]

Theridiidae

Theridiidae is a large family of spiders, also known as the tangle-web spiders, cobweb spiders and comb-footed spiders. The diverse family includes over 2200 species in over 100 genera) of three-dimensional space-web-builders found throughout the world. Theridiid spiders are entelegyne (have a genital plate in the female) araneomorph ecribellate (use sticky capture silk instead of woolly silk) spiders that often build tangle space webs and have a comb of serrated bristles (setae) on the tarsus of the fourth leg. [more]

Theridiosomatidae

The ray spiders (family Theridiosomatidae) are spiders most recognizable for their construction of cone-shaped webs. As of 2008, the family consists of 75 species in 12 genera. [more]

Thomisidae

Crab spider is a common name applied loosely to many species of spiders, but most nearly consistently to members of the family Thomisidae. Among the Thomisidae it refers most often to the familiar species of "flower crab spiders", though not all members of the family are limited to ambush hunting in flowers. [more]

Titanoecidae

The titanoecid spiders (family Titanoecidae) include only five genera and a little over 46 species worldwide. The family is fairly widespread in the New World and Eurasia. Once part of the family Amaurobiidae, these are mostly dark-colored builders of wooly (cribellate) silk webs. The main genus is Titanoeca. Several species are found at relatively high altitudes in mountain ranges and may be very common in such habitats. [more]

Trechaleidae

The Trechaleidae are a spider family with 75 described species in 15 genera. [more]

Trochanteriidae

The Trochanteriidae are a spider family with 149 species in 18 genera. [more]

Uloboridae

Uloboridae, the cribellate orb weavers or hackled orb weavers, is a family of non-venomous spiders. Their lack of poison glands is a secondarily evolved trait. Instead, they kill their prey by crushing with over 140 metres of thread. [more]

Zodariidae

The Zodaraiid ground spiders or ant spiders, are a family (Zodaraiidae) of small to medium-sized eight-eyed spiders. They are found world-wide in tropical to warm temperate regions, though there are relatively few species in North America. [more]

Zoridae

The Zoridae are a spider family with more than 70 described species in 13 genera. [more]

Zorocratidae

Zorocratid spiders are uncommon, somewhat wolf spider-like, wandering spiders. The eye arrangement is not like that of wolf spiders as the posterior eyes are not enlarged and the eyes are in two rows. Little is known of their biology, but they include about 20 species in 5 genera found primarily in Africa, Madagascar, and North America. The North American species all belong to the genus Zorocrates. The genus Uduba is known only from Madagascar. The odd distribution seems to indicate a connection with continental drift and the family was apparently broken up with the final separation of Africa and the Americas. [more]

Zoropsidae

Zoropsidae is a family of uncommon, somewhat wolf spider-like, wandering, cribellate spiders. The eye arrangement is not like that of wolf spiders as the eyes are in two rows and are more equal in size. Little is known of their biology, but they include about 65 species in 12 genera found primarily in Australia and South Africa. One species, Zoropsis spinimana, was accidentally introduced to the United States. [more]

At least 95 species and subspecies belong to the Family Zoropsidae.

More info about the Family Zoropsidae may be found here.

References

• Bilger, Burkhard (5 March 2007). "Spider Woman". The New Yorker: 66–73. http://www.newyorker.com/reporting/2007/03/05/070305fa_fact_bilger. 
• W. S. Bristowe (1976). The World of Spiders. Taplinger Pub Co. ISBN 0-8008-8598-8. 
• Crompton, John (1950). The Life of the Spider. New York: Mentor. 
• Hillyard PD (1994). The book of the spider: from arachnophobia to the love of spiders< /span>. New York: Random House. ISBN 0-679-40881-9. 
• Kaston BJ, Kaston E (1953). How to know the spiders : pictured-keys for determining the more common spiders, with suggestions for collecting and studying them (1st ed.). Dubuque, : W. C. Brown Co.. 
• Main, Barbara York (1975). Spiders. London: Collins. ISBN 0-00-211443-7. 
• Paquin, Pauline; D. Ubick (2005). Spiders of North America: An Identification Manual. American Arachnological Society. ISBN 0-9771439-0-2. 
• Wise, David A. (1993). Spiders in ecological webs. Cambridge, UK: Cambridge University Press. ISBN 0-521-325 47-1. 

Footnotes

1. ^ ^{a b c} Platnick, Norman I. (2009). "The World Spider Catalog, version 9.5". American Museum of Natural History. http://research.amnh.org/entomology/spiders/catalog/COUNTS.html. Retrieved on 2009-04-25. 
2. ^ Foelix, Rainer F. (1996). Biology of Spiders. 198 Madison Ave. NY, New York, 10016: Oxford University Press. p. 3. ISBN 0-19-509593-6. 
3. ^ "Vegetarian Spider". Susan Milius. Science News. 2008-08-30. http://www.sciencenews.org/view/generic/id/35121/title/Vegetarian_spider. Retrieved on 2009-04-09. 
4. ^ Ruppert, E.E., Fox, R.S., and Barnes, R.D. (2004). Invertebrate Zoology (7 ed.). Brooks / Cole. p. 520. ISBN 0030259827. 
5. ^ ^{a b c} Ruppert, E.E., Fox, R.S., and Barnes, R.D. (2004). Invertebrate Zoology (7 ed.). Brooks / Cole. pp. 554–555. ISBN 0030259827. 
6. ^ ^{a b} Ruppert, E.E., Fox, R.S., and Barnes, R.D. (2004). Invertebrate Zoology (7 ed.). Brooks / Cole. pp. 518–522. ISBN 0030259827. 
7. ^ ^{a b c d e f g h i j k l m n o p q r s t u v w x y z aa ab ac ad ae af ag ah ai aj} Ruppert, E.E., Fox, R.S., and Barnes, R.D. (2004). Invertebrate Zoology (7 ed.). Brooks / Cole. pp. 571–584. ISBN 0030259827. 
8. ^ ^{a b c d e f g} Ruppert, E.E., Fox, R.S., and Barnes, R.D. (2004). Invertebrate Zoology (7 ed.). Brooks / Cole. pp. 559–564. ISBN 0030259827. 
9. ^ ^{a b} Ruppert, E.E., Fox, R.S., and Barnes, R.D. (2004). Invertebrate Zoology (7 ed.). Brooks / Cole. pp. 565–569. ISBN 0030259827. 
10. ^ Ruppert, E.E., Fox, R.S., and Barnes, R.D. (2004). Inve rtebrate Zoology (7 ed.). Brooks / Cole. pp. 571-584. ISBN 0030259827. 
11. ^ Ruppert, E.E., Fox, R.S., and Barnes, R.D. (2004). Invertebrate Zoology (7 ed.). Brooks / Cole. pp. 527–528. ISBN 0030259827. 
12. ^ ^{a b c} Coddington, J.A. & Levi, H.W. (1991). "Systematics and Evolution of Spiders (Araneae)". Annu. Rev. Ecol. Syst. 22: 565–592. doi:10.1146/annurev.es.22.110191.003025. 
13. ^ ^{a b} Ruppert, E.E., Fox, R.S., and Barnes, R.D. (2004). Invertebrate Zoology (7 ed.). Brooks / Cole. pp. 529–530. ISBN 0030259827. 
14. ^ ^{a b} Ruppert, E.E., Fox, R.S., and Barnes, R.D. (2004). Invertebrate Zoology (7 ed.). Brooks / Cole. pp . 531–532. ISBN 0030259827. 
15. ^ ^{a b c d} Ruppert, E.E., Fox, R.S., and Barnes, R.D. (2004). Invertebrate Zoology (7 ed.). Brooks / Cole. pp. 532–537. ISBN 0030259827. 
16. ^ Ruppert, E.E., Fox, R.S. , and Barnes, R.D. (2004). Invertebrate Zoology (7 ed.). Brooks / Cole. pp. 578–580. ISBN 0030259827. 
17. ^ ^{a b c} Harland, D.P., and Jackson, R.R. (2000). "PDF “Eight-legged cats” and how they see - a review of recent research on jumping spiders (Araneae: Salticidae)". Cimbebasia 16: 231–240. http://www.cogs.susx.ac.uk/ccnr/Papers/Downloads/Harland_Cimb2000.pdf PDF. Retrieved on 2008-10-11. 
18. ^ Barnes, R.S.K., Calow, P ., Olive, P., Golding, D., and Spicer, J. (2001). "Invertebrates with Legs: the Arthropods and Similar Groups". The Invertebrates: A Synthesis. Blackwell Publishing. p. 168. ISBN 0632047615. http://books.google.co.uk/books?id=TBMsbe9efPgC&pg=PA168&dq=arthropod+hydraulic&sig=ACfU3U2C PJ_K9DDSTNMoj97Mutbl8DFLgg. Retrieved on 2008-09-25. 
19. ^ Parry, D.A., and Brown, R.H.J. (1959). "The Hydraulic Mechanism of the Spider Leg" (PDF). Journal of Experimental Biology 36: 423–433. http://jeb.biologists.org/cgi/reprint/36/2/423.pdf. Retrieved on 2008-09-25. 
20. ^ Anderson, D.T. (2001), "The Chelicerata", in Anderson, D.T., Invertebrate Zoology (2 ed.), Oxford University Press, pp. 325–349, ISBN 0195513681 
21. ^ Vollrath, F., and Knight, D.P. (March 2001). "Liquid crystalline spinning of spider silk". Nature 410: 541–548. doi:10.1038/35069000. 
22. ^ Ruppert, E.E., Fox, R.S., and Barnes, R.D. (2004). Invertebrate Zoology (7 ed.). Brooks / Cole. pp. 537–539. ISBN 0030259827. 
23. ^ Knoflach, B. & van Harten, A. (2001). "Tidarren argo sp. nov (Araneae: Theridiidae) and its exceptional copulatory behaviour: emasculation, male palpal organ as a mating plug and sexual cannibalism". Journal of Zoology 254: 449–459. doi:10.1017/S0952836901000954 . 
24. ^ Andrade, Maydianne C.B. (2003). "Risky mate search and male self-sacrifice in redback spiders". Behavioral Ecology 14: 531–538. doi:10.1093/beheco/arg015. 
25. ^ ^{a b} < sup>c ^d Foelix, R.F. (1996). "Reproduction". Biology of Spiders. Oxford University Press US. pp. 176–212. ISBN 0195095944. http://books.google.co.uk/books?id=XUgyqxNKhyAC&dq=%22Biology+of+Spiders%22+Foelix&pg=PP1&ots=Ch4j60g2pL&sig=42rE8UvdN74f4pcxzWLAniivNaY&hl=en&sa=X&oi=book_result&resnum=4&ct=result#PPA176,M1. Retrieved on 2008-10-08. 
26. ^ Ruppert, E.E., Fox, R.S., and Barnes, R.D. (2004). Invertebrate Zoology (7 ed.). Brooks / Cole. pp. 523–524. ISBN 0030259827. 
27. ^ Spiders and their Kin, Herbert W. Levi and Lorna R. Levi, Golden Press, p. 20 and p. 44
28. ^ ^{a b c d e} Oxford, G.S. & Gillespie, R.G. (1998). Evolution and Ecology of Spider Coloration. Annual Review of Entomology 43:619-643. doi:10.1146/annurev.ento.43.1.619
29. ^ ^{a b c} Meehan, C,J. Olson, E.J. and Curry, R.L. (21 August 2008), Exploitation of the Pseudomyrmex–Acacia mutualism by a predominantly vegetarian jumping spider (Bagheera kiplingi), http://eco.confex.com/eco/2008/techprogram/P12401.HTM, retrieved on 2008-10-10 
30. ^ ^{a b} Jackson, R.R. et al. (2001). "Jumping spiders (Araneae: Salticidae) that feed on nectar" (PDF). J. Zool. Lond. 255: 25–29. doi:10.1017/S095283690100108X. http://xnelson.googlepages.com/Jacksonetal2001.pdf. 
31. ^ Schütz, D., and Taborsky, M. (2003). "Adaptations to an aquatic life may be responsible for the reversed sexual size dimorphism in the water spider, Argyroneta aquatica" (PDF). Evolutionary Ecology Research 5 (1): 105–117. http://www.zoology.unibe.ch/behav/pdf_files/Schuetz_EvolEcolRes03.pdf. Retrieved on 2008-10-11. 
32. ^ Coddington, J., and Sobrevila, C. (1987). "Web manipulation and two stereotyped attack behaviors i n the ogre-faced spider Deinopis spinosus Marx (Araneae, Deinopidae)." (PDF). Journal of Arachnology 15: 213–225. http://www.americanarachnology.org/JoA_free/JoA_v15_n2/JoA_v15_p213.pdf. Retrieved on 2008-10-11. 
33. ^ Eberhard, W.G. (December 1977). "Aggressive Chemical Mimicry by a Bolas Spider" (PDF). Science 198 (4322): 1173–1175. doi:10.1126/science.198.4322.1173. PMID 17818935. http://striweb.si.edu/publications/PDFs/Eberhard_Agreessive%20chemical%20mimicry.Science.1977.pdf. Retrieved on 2008-10-10. 
34. ^ Eberhard, W.G. (1980). "The Natural History and Behavior of the Bolas Spider, Mastophora dizzydeani sp. n. (Araneae)". Psyche 87: 143–170. doi:10.1155/1980/81062. http://psyche.entclub.org/87/87-143.html. Retrieved on 2008-10-10. 
35. ^ Yeargan, K.V., and Quate, L.W. (1997). "Adult male bolas spiders retain juvenile hunting tactics". Oecologia 112 (4): 572–576. doi:10.1007/s004420050347. 
36. ^ ^{a b} Wilcox, S. and Jackson, R. (2002). "Jumping Spider Tricksters". in Bekoff, M., Allen, C., and Burghardt, G.M.. The Cognitive Animal: Empirical and Theoretical Perspectives on Animal Cognition. MIT Press. pp. 27–34. ISBN 0262523221. 
37. ^ Mclver, J.D. and Stonedahl, G. (January 1993). "Myrmecomorphy: Morphological and Behavioral Mimicry of Ants". Annual Review of Entomology 38: 351–377. doi:10.1146/annurev.en.38.010193.002031. 
38. ^ "Different smiles, single species". University of California Museum of Paleontology. http://evolution.berkeley.edu/evolibrary/article/_0_0/happyface_03. Retrieved on 2008-10-10. 
39. ^ Cooke, J.A.L., Roth, V.D., and Miller, F.H.. "The urticating hairs of theraphosid sp iders". American Museum novitates (American Museum of Natural History) (2498). http://digitallibrary.amnh.org/dspace/handle/2246/2705. Retrieved on 2008-10-11. 
40. ^ Blackledge, T.A., and Wenzel, J.W. (2001). "Silk Mediated Defense by an Orb Web Spider against Predatory Mud-dauber Wasps". Behaviour 138 (2): 155–171. doi:10.1163/15685390151074357. 
41. < a href="#cite_ref-40">^ Armstrong, S. (14 July 1990). "Fog, wind and heat - life in the Namib desert". New Scientist. http://www.newscientist.com/article/mg12717253.800-fog-wind-and-heat--life-in-the-namib-desert-researchersworking-in-one-of-the-worlds-most-hostile-environments-are-discoveringhowscores-of-species-manage-to-survive-but-will-the-research-station-itselfsurvive-as-namibia-gains-its-independence-.html. Retrieved on 2008-10-11. 
42. ^ Vollrath, F. (1986). "Eusociality and extraordinary sex ratios in the spi der Anelosimus eximius (Araneae: Theridiidae)". Behavioral Ecology and Sociobiology, 18 (4): 283–287. doi:10.1007/BF00300005. 
43. ^ Agnarsson, I., and Kuntner, M. (April 2005). "Madagascar: an unexpected hotspot of social Anelosimus spider diversity (Araneae: Theridiidae)". Systematic Entomology 30 (4): 575–592. doi:10.1111/j.1365-3113.2 005.00289.x. 
44. ^ Avilés, L., Maddison, W.P. and Agnarsson, I. (August 2006). "A New Independently Derived Social Spider with Explosive Colony Proliferation and a Female Size Dimorphism". Biotropica 38 (6): 743–753. doi:10.1111/j.1744-7429.2006.00202.x. 
45. ^ Matsumoto, T. (1998). "Cooperative prey capture in the communal web spider, Philoponella raffray (Araneae, Uloboridae)" (PDF). Journal of Arachnology 26: 392–396. http://www.americanarachnology.org/JoA_free/JoA_v26_n3/JoA_v26_p392.pdf. Retrieved on 2008-10-11. 
46. ^ Cangialosi, K.R. (July 1990). "Social spider defense against kleptoparasitism". Behavioral Ecology and Sociobiology 27 (1). doi:10.1007/BF00183313. 
47. ^ Bertani, R., Fukushima, C.S., and Martins, R. (May 2008). "Sociable widow spiders? Evidence of subsociality in LatrodectusWalckenaer, 1805 (Araneae, Theridiidae)". Journal of Ethology 26 (2): 299. doi:10.1007/s10164-007-0082-8. 
48. ^ ^{a b c d e} Eberhard, W.G. (1990). "Function and Phylogeny of Spider Webs" (PDF). Annual Reviews in Ecology and Systematics 21: 341–372. doi:10.1146/annurev.es.21.110190.002013. http://striweb.si.edu/publications/PDFs/Eberhard_Function%20and%20Phylogeny%20of.Annual%20Review%20of%20Ecology%20and%20Syst.1990.pdf. Retrieved on 2008-10-15. 
49. ^ ^{a b} Agnarsson, I. (2004). "Morphological phylogeny of cobweb spiders and their relatives (Araneae, Araneoidea, Theridiidae)". Zoological Journal of the Linnean Society 141 (4): 447–626. doi:10.1111/j.1096-3642.2004.00120.x. 
50. ^ Herberstein, M.E. (2). "Australian Journal of Zoology". Australian Journal of Zoology 48: 217–223. doi:10.1071/ZO00007. 
51. ^ Li, D., and Lee, W.S. (February 2004). "Predator-induced plasticity in web-building behaviour". Animal Behaviour 67 (2): 309–318. doi:10.1016/j.anbehav.2003.06.011. 
52. ^ Thomson, Peggy and Park, Edwards. "Odd Tales from the Smithsonian". http://smithsonianeducation.org/students/secrets_of_the_Smithsonian/spiders_in_space.html. Retrieved on 2008-07-21. 
53. ^ Schütt, K. (1995). "Drapetisca socialis (Araneae: Linyphiidae): Web reduction - ethological and morphological adaptations" (PDF). European Journal of Entomology 92: 553–563. http://www.eje.cz/pdfarticles/599/ eje_092_3_553_Schutt.pdf. Retrieved on 2008-10-19. 
54. ^ Schultz, J.W. (2007). "A phylogenetic analysis of the arachnid orders based on morphological characters". Zoological Journal of the Linnean Society 150: 221–265. doi:10.1111/j.1096-3642.2007.00284.x. 
55. ^ Selden, P.A., Anderson, H.M. & Anderson, J.M. 2009. A review of the fossil record of spiders (Araneae) with special reference to Africa, and description of a new specimen from the Triassic Molteno Formation of South Africa. African Invertebrates 50 (1): 105-116. Abstract PDF
56. ^ ^{a b} Penney, D., and Selden, P.A. (2007). "Spinning with the dinosaurs: the fossil record of spiders". Geology Today 23 (6): 231–237. doi:10.1111/j.1365-2451.2007.00641.x. 
57. ^ Hecht, H.. "Oldest spider web found in amber". New Scientist. http://www.newscientist.com/article/dn9389-oldest-spider-web-found-in-amber.html. Retrieved on 2008-10-15. 
58. ^ Dunlop, J.A. (September 1996). "A trigonotarbid arachnid from the Upper Silurian of Shropshire" (PDF). Palaeontology 39 (3): 605–614. http://palaeontology.palass-pubs.org/pdf/Vol%2039/Pages%20605-614.pdf. Retrieved on 2008-10-12.  The fossil was originally named Eotarbus but was renamed when it was realized that a Carboniferous arachnid had already been named Eotarbus: Dunlop, J.A.. "A replacement name for the trigonotarbid arachnid Eotarbus Dunlop". Palaeontology 42 (1): 191. 
59. ^ ^{a b c d e} Vollrath, F., and Selden, P.A. (December 2007). "The Role of Behavior in the Evolution of Spiders, Silks, and Webs" (PDF). Annual Review of Ecology, Evolution, and Systematics 38: 819–846. doi:10.1146/annurev.ecolsys.37.091305.110221. http://homepage.mac.com/paulselden/Sites/Website/ARES.pdf. Retrieved on 2008-10-12. 
60. ^ Selden, P.A., and Shear, W.A. (July 2008). "Fossil evidence for the origin of spider spinnerets" (PDF). Nature Precedings. http://precedings.nature.com/documents/2088/version/1/files/npre20082088-1.pdf. Retrieved on 2008-10-12. 
61. ^ Selden, P.A. (February 1996). "Fossil mesothele spiders". Nature 379: 498–499. doi:10.1038/379498b0. 
62. ^ ^{a b c d} Shultz, J.W. (2007). "A phylogenetic analysis of the arachnid orders based on morphological characters". Zoolog ical Journal of the Linnean Society 150: 221–265. doi:10.1111/j.1096-3642.2007.00284.x. 
63. ^ Gould, S.J. (1990). Wonderful Life: The Burgess Shale and the Nature of History. Hutchinson Radius. p. 105. ISBN 0091742714. 
64. ^ ^{a b c d e f g} Coddington, J.A. (2005) . "Phylogeny and Classification of Spiders". in Ubick, D., Paquin, P., Cushing, P.E., and Roth, V. (PDF). Spiders of North America: an identification manual. American Arachnological Society. pp. 18–24. ISBN 0977143902. http://si-pddr.si.edu/dspace/bitstream/10088/4365/1/CoddingtonSNAPhylogeny05.pdf. Retrieved on 2008-10-12. 
65. ^ ^{a b} Leroy, J, and Leroy, A. (2003). "How spiders function". Spiders of Southern Africa. Struik. pp. 15–21. ISBN 1868729443. http://books.google.co.uk/books?id=zgxfRnYbiYcC&dq=mesothe lae+venom+spinnerets&source=gbs_summary_s&cad=0. Retrieved on 2008-10-12. 
66. ^ Ono, H. (2002). "New and Remarkable Spiders of the Families Liphistiidae, Argyronetidae, Pisauridae, Theridiidae and Araneidae (Arachnida) from Japan". Bulletin of the National Science Museum (of Japan), Series A 28 (1 pages= 51-60). 
67. ^ Coyle, F.A. (1986). "The Role of Silk in Prey Capture". in Shear, W.A.. Spiders--webs, behavior, and evolution. Stanford University Press. pp. 272–273. ISBN 0804712034. 
68. ^ Forster, R. R., and Platnick, N.I. (1984). "A review of the archaeid spiders and their relatives, with notes on the limits of the superfamily Palpimanoidea (Arachnida, Araneae)" (abstract). Bulletin of the American Museum of Natural History 178: 1–106. http://hdl.handle.net/2246/991. Retrieved on 2008-10-13.  Full text at "A review of the archaeid spiders and their relatives" (PDF). http://digitallibrary.amnh.org/dspace/bitstream/2246/991/1/B178a01.pdf. Retrieved on 2008-10-13.  (60 MB)
69. ^ Penney, D., and Selden, P.A.. Assembling the Tree of Life—Phylogeny of Spiders: a review of the strictly fossil spider families. in Deltshev, C., and Stoev, P.. "Eropean Arachnology 2005" (PDF). Acta Zoologica Bulgarica Supplement No. 1: 25–39. http://homepage.mac.com/paulselden/Sites/Website/Bulgaria.pdf. Retrieved on 2008-10-13. 
70. ^ "Natural history of Mygalomorphae". Agricultural Research Council of New Zealand. http://www.arc.agric.za/home.asp?pid=4163. Retrieved on 2008-10-13. 
71. ^ Spider Bite Symptoms and First Aid By Rod Brouhard, About.com. Updated: October 19, 2008
72. ^ "Spiders". Illinois Department of Public Health. http://www.idph.state.il.us/envhealth/pcspiders.htm. Retrieved on 2008-10-11. 
73. ^ Vetter RS, Barger DK (November 2002). "An infestation of 2,055 brown recluse spiders (Araneae: Sicariidae) and no envenomations in a Kansas home: implications for bite diagnoses in nonendemic areas". J Med Entomol. 39 (6): 948–51. PM ID 12495200. 
74. ^ Hannum, C.and Miller, D.M.. "Widow Spiders". Department of Entomology, Virginia Tech. http://www.ext.vt.edu/pubs/entomology/444-422/444-422.html. Retrieved on 2008-10-11. 
75. ^ "Funnel web spiders". Australian Venom Research Unit. http://www.avru.org/compendium/biogs/A000003b.htm. Retrieved on 2008-10-11. 
76. ^ "Pub chef bitten by deadly spider". BBC. http://news.bbc.co.uk/1/hi/england/somerset/4489033.stm. Retrieved on 2008-10-11. 
77. ^ Diaz, J.H. (01 August 2004). "The Global Epidemiology, Syndromic Classification, Management, and Prevention of Spider Bites". American Journal of Tropical Medicine and Hygiene 71 (2): 239–250. PMID 15306718. http://www.ajtmh.org/cgi/content/abstract/71/2/239. 
78. ^ Williamson, J.A., Fenner, P.J., Burnett, J.W., and Rifkin, J. (1996). Venomous and Poisonous Marine Animals: A Medical and Biological Handbook. UNSW Press. pp. 65–8. ISBN 0868402796. http://books.google.co.uk/books?id=YsZ3GryFIzEC&pg=PA75&lpg=PA75&dq=mollusc+venom+fatal&source=web&ots=tBDHW2xdlx&sig=PAvTz2z3hnwUyE4lfU8fvzwNbD4&hl=en&sa=X&oi=book_result&resnum=2&am p;ct=result#PPA57,M1. Retrieved on 2008-10-03. 
79. ^ Nishioka, S de A. (August 2001). "Misdiagnosis of brown recluse spider bite". Western Journal of Medicine 175 (2): 240. PMID 11290673. 
80. ^ Isbister GK (April 2001). "Spider mythology across the world". Western Journal of Medicine 174 (4): 86–7. doi:10.1136/ewjm.175.2.86. PMID 11483545. 
81. ^ Ray, N. (2002). Lonely Planet Cambodia. Lonely Planet Publications. p. 308. ISBN 1-74059-111-9. 
82. ^ Weil, C. (2006). Fierce Food. Plume. ISBN 0452287006. http://www.budgettravel.com/bt-dyn/content/article/2006/10/24/AR2006102400797.html. Retrieved on 2008-10-03. 
83. ^ "Spider Venom Could Yield Eco-Friendly Insecticides". National Science Foundation (USA). http://www.nsf.gov/discoveries/disc_summ.jsp?cntn_id=100676&org=NSF. Retrieved on 2008-10-11. 
84. ^ Novak, K. (2001). "Spider venom helps hearts keep their rhythm". Nature Medicine 7 (155): 155. doi:10.1038/84588. 
85. ^ Lewis, R.J., and Garcia, M.L. (October 2003). " Therapeutic potential of venom peptides" (PDF). Nature Reviews Drug Discovery 2: 790–802. doi:10.1038/nrd1197. http://imb.uq.edu.au/download/large/Venom_therapeutics.pdf. Retrieved on 2008-10-11. 
86. ^ Bogin, O. (Spring 2005). "Venom Peptides and their Mimetics as Potential Drugs" (PDF). Modulator (19). http://www.alomone.com/System/UpLoadFiles/DGallery/Docs/Venom%20Peptides%20and%20their%20Mimetics%20as%20Potential%20Drugs.pdf. Retrieved on 2008-10-11. 
87. ^ Andrade E, Villanova F, Borra P, et al (June 2008). "Penile erection induced in vivo by a purified toxin from the Brazilian spider Phoneutria nigriventer". British Journal of Urology International 102 ( 7): 835–7. doi:10.1111/j.1464-410X.2008.07762.x. 
88. ^ Hinman, M.B., Jones J.A., and Lewis, R.W. (September 2000). "Synthetic spider silk: a modular fiber" (PDF). Trends in Biotechnology 18 (9): 374–9. doi:10.1016/S0167-7799(00)01481-5. http://www.tech.plym.ac.uk/sme/FailureCases/Natural_Structures/Synthetic_spider_silk.pdf. Retrieved on 2008-10-19. 
89. ^ Menassa, R., Zhu, H., Karatzas, C.N., Lazaris, A., Richman, A., and Brandle, J. (June 2004). "Spider dragline silk proteins in transgenic tobacco leaves: accumulation and field production". Plant Biotechnology Journal 2 (5): 431–8. doi:10.1111/j.1467-7652.2004.00087.x. 
90. ^ "A Common Phobia". phobias-help.com. Archived from the original on 2009-08-02. http://www.webcitation.org/5ijWR89tc. Retrieved on 2009-08-02. "There are many common phobias, but surprisingly, the most common phobia is arachnophobia." 
91. ^ Fritscher, Lisa (2009-06-03). "Spider Fears or Arachnophobia". Phobias. About.com. Archived from the original on 2009-08-02. http://www.webcitation.org/5ijWgAjUW. Retrieved on 2009-08-02. "Arachnophobia, or fear of spiders, is one of the most common specific phobias." 
92. ^ "The 10 Most Common Phobia s - Did You Know?". 10 Most Common Phobias. Archived from the original on 2009-08-02. http://www.webcitation.org/5ijXFN004. Retrieved on 2009-08-02. "Probably the most recognized of the 10 most common phobias, arachnophobia is the fear of spiders. The statistics clearly show that more than 50% of women and 10% of men show signs of this leader on the 10 most common phobias list." 
93. ^ Friedenberg, J., and Silverman, G. (2005). Cognitive Science: An Introduction to the Study of Mind. SAGE. pp. 244–245. ISBN 1412925681. http://books.google.co.uk/books?id=wGti6_4Qn_QC&pg=PA244&dq=Arachnophobia&lr=&sig=ACfU3U2bQYuqAO7EUfWM6MCqFu-Jy-COAA#PPA244,M1. Retrieved on 2008-10-11. 
94. ^ Davey, G.C.L. (1994). "The “Disgusting” Spider: The Role of Disease and Illness in the Perpetuation of Fear of Spiders". Society and Animals 2 (1): 17–25. doi:10.1163/156853094X00045. 
95. ^ De Vos, Gail (1996). Tales, Rumors, and Gossip: Exploring Contemporary Folk Literature in Grades 7-12. Libraries Unlimited. pp. 186. ISBN 1563081903. http://books.google.com/books?id=M8bvN93y-fIC&pg=PA186&dq=spiders+folklore+and+mythology&lr=&ei=HHsNSNGgNZOKsgO2sqnHAQ&sig=rfYxr-r7pktGmHuA31vEUL99rn8. Retrieved on 2008-04-22. 
96. ^ Garai, Jana (1973). The Book of Symbols. New York: Simon & Schuster. ISBN 671-21773-9. 
97. ^ De Laguna et al, Frederica (2002). American Anthropology: Papers from the American Anthropologist. Unive rsity of Nebraska Press. pp. 455. ISBN 080328280X. http://books.google.com/books?id=XIFX-sSYURwC&pg=PA455&dq=Spider+creation+myth&sig=RI0W9BNC-E36_Le7G2bMvhbjQNw. Retrieved on 2008-04-21. 
98. ^ Benson, Elizabeth, The Mochica: A Culture of Peru. New York, NY: Praeger Press. 1972
99. ^ Berrin, Katherine & Larco Museum. The Spirit of Ancient Peru:Treasures from the Museo Arqueológico Raf ael Larco Herrera. New York: Thames and Hudson, 1997.

Further Reading

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• Bilger, Burkhard (5 March 2007). "Spider Woman". The New Yorker (A Reporter at Large (column)): 66?73. http://www.newyorker.com/reporting/2007/03/05/070305fa_fact_bilger. 
• Bristowe, W. S. (1976). The World of Spiders. Taplinger Publishing Company. ISBN 0800885988. OCLC 256272177. 
• Crompton, John (1950). The Life of the Spider. New York: Mentor. OCLC 1979220. 
• Hillyard, Paul (1994). The Book of the Spider: From Arachnophobia to the Love of Spiders. New York: Random House. ISBN 0679408819. OCLC 35231232. 
• Kaston, B. J.; Elizabeth Kaston (1953). How t o Know the Spiders; Pictured-Keys for Determining the More Common Spiders, with Suggestions for Collecting and Studying Them (1st ed.). Dubuque, Iowa: W. C. Brown Company. OCLC 628203833. 
• Main, Barbara York (1975). Spiders. Sydney: Collins. ISBN 0002114437. OCLC 123151744. 
• Wise, David A. (1993). Spiders in Ecological Webs. Cambridge studies in ecology. Cambridge, UK: Cambridge University Press. ISBN 0521325471. OCLC 25833874. 

External links

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• Spiders at the Open Directory Project
• Picture st ory about the jumping spider Aelurillus v-insignitus
• Online Videos of Jumping Spiders (Salticids) and other arachnids
• Spider at the Encyclopedia of Life
• list of field guides to spiders, from the International Field Guides database

Sources

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• The text on this page is licensed under the GNU Free Documentation License. It includes material from Wikipedia retrieved Wednesday, April 25, 2012.
• Photographs on this page are copyrighted by individual photographers, and individual copyrights apply.
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