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From Wikipedia, the free encyclopedia
True tarantulas are spiders belonging to the family Theraphosidae (Greek for thera "wild animal, beast" + phos "light"). These spiders may also be known as bird spiders, monkey spiders, baboon spiders or rain spiders. They are characterized by having tarsi (feet) with two claws and claw tufts, called scopulae. Related families include the funnel-web spiders and the trap door spiders, which sometimes also get called tarantulas. The family Theraphosidae includes over 800 different species of tarantulas, divided over 12 subfamilies (formerly 13) and 11 genera.
This article primarily discusses the true tarantulas; however the history of the name "tarantula", as well as other spiders referred to by the term, are discussed below.
This article refers to true tarantulas of the family Theraphosidae.
Tarantulas are long-legged, long-living spiders, whose entire body is covered with short glittery hairs called setae. Tarantulas inhabit tropical to temperate regions in South America and Central America, Mexico, and the southwestern United States, Asia, Southern Europe, Africa and Australia. In South Africa they are sometimes referred to as Baboon Spiders.
The body of the tarantula pictured to the left is approximately 2.5 inches (6.2 cm) long. Despite their often scary appearance and reputation, none of the true tarantulas are included in the list of deadly spiders (spiders having a strong toxin, dangerous to humans), and this particular kind of tarantula is regarded as especially docile. Some people claim that there exist deadly varieties of tarantulas somewhere in South America, a theory which provides the basis of the story in the American film Arachnophobia. This claim is often made without identifying a particular spider although the "banana tarantula" is sometimes named. The dangerous Brazilian wandering spider (Phoneutria nigriventer) is probably the spider in question as it is sometimes found hiding in clusters of bananas and is one of several spiders called the "banana spider." It is not a tarantula but it is fairly large (about an inch long), somewhat hairy, and is regarded as aggressive. However, the Sydney funnel-web spider (Atrax robustus), is perhaps the most aggressive, highly venomous, and likely to bite repeatedly and envenomate enthusiastically. It is a species of the venomous funnel-web tarantulas, a member of the same suborder as the true tarantulas but not one of the Theraphosidae.
Size, Color and Type
Tarantulas are not all large. Depending on the species, their body length may vary from 1-4 inches (2.5 - 10 cm), with 3 to 12 inch (8-30 cm) leg spans (their size when including their legs). Size is measured by measuring from the tip of the back leg to the tip of the front leg on the same side. The largest species of tarantulas can weigh over 3 ounces (90 grams). The Goliath birdeater (Theraphosa blondi) from Venezuela and Brazil is generally regarded to be the largest species, however some breeders and hobbyists believe otherwise. The Pinkfoot goliath tarantula (Theraphosa apophysis) was described 187 years after the goliath birdeater; therefore it is not as well-known. However legspans of up to 13 inches have been reported. In general the males of most species are slimmer and longer legged than the females.
The majority of tarantulas are brown or black, however some species have more extensive coloration patterns, ranging from cobalt blue (cobalt blue tarantula, Haplopelma lividum), black with white stripes (pink zebra beauty or Eupalaestrus campestratus and Brazilian giant white knee tarantula or Acanthoscurria geniculata) to metallic blue legs with vibrant orange abdomen (greenbottle blue tarantula, Chromatopelma cyaneopubescens). Their natural habitats include savanna, grasslands such as the pampas, rainforests, deserts, scrubland, mountains and cloud forests. They are generally divided into terrestrial types (that frequently make burrows) and arboreal types.
Many tarantula species exhibit pronounced sexual dimorphism. Males tend to be smaller (especially the abdomen) and may be quite colourful, as in the very large Bolivian and Peruvian species Pamphobeteus antinous, in which the female is dark brown and the male shiny iridescent purple. Males also tend to have shorter lifespans. For these reasons, most tarantulas kept as pets are female.
Besides the normal hairs covering the body of tarantulas, some also have a dense covering of irritating hairs (about 10,000 per mm² ), called urticating hairs, on the opisthosoma, that they sometimes use as a protection against enemies. These hairs are only present on some New World species of the subfamilies of Ischnocolinae, Aviculariinae, Grammostolinae and Theraphosinae ) and are absent on specimens of the Old World. They help in phylogenetic studies of Theraphosinae .
Hairy Chaetopelma sp.These fine hairs are barbed, and designed to urticate, but do not contain venom. They count . Some species can 'kick off' these hairs: the hairs are launched into the air at a target. Tarantulas also use these hairs for other means. They mark their territories with these hairs, using them to mark territory or to line the web or nest (the latter such practice may discourage flies from feeding on the spiderlings).
To predators and other kinds of enemies, these hairs can range from being lethal to simply being a deterrent. With humans, they can cause irritation to eyes, nose, and skin, and more dangerously, the lungs and airways, if inhaled. The symptoms range from species to species, from person to person, from a burning itch to a minor rash. Tarantula hair has been used as the main ingredient in the novelty item "itching powder." Some tarantula enthusiasts have had to give up their spiders because of allergic reactions to these hairs (skin rashes, problems with breathing, and swelling of the affected area).
Habitat and Behavior
Tarantulas are nocturnal predators, killing their prey by injecting venom through their fangs. The hungry tarantula typically waits partially hidden at the entrance to its retreat to ambush passing prey. It has sensitive hairs that enable it to detect the size and location of potential victims from the vibrations caused by their movements. Some species also use their silk fiber to detect motion (when a prey trigger a line). Like many other spiders, it cannot see much more than light, darkness, and movement (see spiders for more about their eyesight), and uses its sense of touch to perceive the world around it. That being said, they are anything but sloppy or imprecise about the way they capture their prey. They generally seem to choose prey on the basis of how dangerous they are perceived to be, the general size of the potential prey animal, etc. Some tarantulas succeed in occasionally capturing small birds, small mammals such as mice, and even small fish, but their ordinary prey consists of insects such as crickets (for ground dwellers) and moths (for arboreal species).
Tarantulas live in a variety of nests. Burrowing tarantulas live underground, in burrows. These burrows are either dug by the spider itself, or else they reuse burrows abandoned by rodents or other small creatures, or they find ready-made crevices. The tunnels are lined with silk and a webbed rim is formed at the entrance so as to conceal it. Other tarantulas make their homes under rocks or tree trunks or under the loose bark of trees. Still others build silken nests on trees, cliff faces, the walls of buildings or in plants such as bananas and pineapples. Tarantulas are well suited for climbing. Even heavy-bodied terrestrial tarantulas such as Grammostola rosea can climb vertical sheets of glass, but climbing very high presents a serious danger to them since any substantial fall can rupture their abdomens. The arboreal species are lighter of body and more able to withstand substantial falls.
Growth, Life, and Mating
Like other spiders, tarantulas have to shed their exoskeleton periodically in order to grow, a process called molting. Young tarantulas may do this several times a year, while full grown specimens will only molt once every year or so, or sooner in order to replace lost limbs or lost urticating hairs.
Tarantulas may live for many years--most species taking 2 to 5 years to reach adulthood, but some species may take up to 10 years to reach full maturity. Upon reaching adulthood, males have typically have but a 1 to 1.5 year period left to live and will immediately go in search of a female with which to mate. It is rare that upon reaching adulthood the male tarantula will molt again.
The habit of male spiders wandering in search of mates makes them especially visible. In late summer and early autumn (September and October in the northern hemisphere), the males will leave their hiding places and walk about, hoping to encounter the hiding place of a female with which to mate. They are willing to cross roads and trails in this quest, and that is when they are most likely to be observed.
When the mature male encounters the burrow of a female, he will draw the female out and signal his intentions to mate by vibrating his body and tapping his front legs. If the female is receptive to mating, she will also vibrate and tap her legs. After mating, the male must get away quickly, or it is possible that he will be eaten. A female tarantula who is unreceptive to mating may also eat the male if he attempts to mate. This result, however, is less common among tarantulas than other spiders. Certain species of tarantulas have been known to mate multiple times over the course of several weeks.
Since females will continue to molt after reaching maturity, they are able to regenerate lost limbs and increase their lifespan. Female specimens have been known to reach 30 years of age and even 40 years, and have survived on water alone for up to 2.5 years. If well cared for, females can expect to live 20-30 years and males 10-12 years, depending on the species.
As with other spiders, the mechanics of intercourse are quite different from those of mammals. Once they reach maturity and become motivated to mate, male spiders will weave a web mat on a flat surface. They then rub their abdomens on the surface of this mat and so doing causes them to release a quantity of semen onto the mat. They then insert their pedipalps (the short leg-like appendages between their chelicerae and their front legs) into the pool of semen. The pedipalps absorb the semen and maintain it in viable condition for sufficient time for the male spider to find a suitable female spider with whom to mate. When a male spider detects the presence of a female he must first exchange signals with her to establish the fact that they are members of the same species and to lull the female into a receptive state. Then the male approaches the female and inserts his pedipalps into the appropriate opening in the lower surface of her abdomen. After the semen has been transferred to the receptive female's body, the male will generally be well advised to leave the scene before the female recovers her appetite.
The females deposit 50 to 2000 eggs, depending on the species, in a silken egg sac and guard it for 6 to 7 weeks. The young spiderlings remain in the nest for some time after hatching and then disperse by crawling in all directions.
Tarantulas usually live in solitude and will attack others of their own kind. There are however exceptions, such as the pinktoe tarantula (Avicularia avicularia), which can be kept communally. Keep in mind ALL tarantulas are cannibalistic; it is always possible one tarantula will eat another. Avicularia Spp. are simply more tolerant of each other. If the vivarium is big enough, has enough hiding spots, and the specimens are about the same size and well fed, there should be little or no cannibalism. Keeping tarantulas communally is not recommended and should not be attempted except by experienced keepers.
Bites and Treatment
There are no substantiated reports of tarantula bites proving fatal to a human, though there have been reports that a Chinese bird spider may have killed a small child in southern China. In general, though, the effects of the bites of all kinds of tarantulas are not well known. While the bites of many species are known to be no worse than a wasp sting, accounts of bites by some species are reported to be very painful. There might indeed be deadly tarantulas of some kind, but no human has yet provoked one of them sufficiently to get a fully envenomated bite. Because other proteins are included when a toxin is injected, some individuals may suffer severe symptoms due to an allergic reaction rather than to the venom. For both those reasons, and because any deep puncture wound can become infected, care should be taken not to provoke any tarantula into biting. Tarantulas are known to have highly individualistic responses. Some members of species generally regarded as aggressive can be rather easy to get along with, and sometimes a spider of a species generally regarded as docile can be provoked. Anecdotal reports indicate that it is especially important not to surprise a tarantula.
New world tarantulas (those found in North and South America) are equipped with urticating hairs on their abdomen, and will almost always use these as a first line of defense. These hairs will irritate sensitive areas of the body and especially seem to target curious animals who may sniff these hairs into the mucous membranes of the nose. These hairs generally do not irritate the hands or other tough areas of skin. Some species have more effective urticating hairs than others. The goliath birdeater is one species known for its particularly irritating urticating hairs. Old world tarantulas (from Asia) have no urticating hairs, and are more likely to attack when disturbed. Old world tarantulas often have more potent, medically significant venom.
Before biting, tarantulas may signal their intention to attack by rearing up into a "threat posture", which may involve raising their prosoma and lifting their front legs into the air, spreading and extending their fangs, and (in certain species) making a loud hissing noise called Stridulating. Their next step, short of biting, may be to slap down on the intruder with their raised front legs. If that response fails to deter the attacker they may next turn away and flick urticating hairs toward the pursuing predator. Their next response may be to leave the scene entirely, but, especially if there is no line of retreat, their next response may also be to whirl suddenly and bite. Tarantulas can be very deceptive in regard to their speed because many of them move very slowly, creating the impression that they could not possibly move as rapidly as they actually can.
First Aid for Bites
Encourage bleeding to wash out the puncture wounds from within. Then clean the bite site with soap and water and protect it against infection. As with other puncture wounds, antiseptics may be of limited use since they may not penetrate to the full depth of a septic wound, so wounds should be monitored for heat, redness, or other signs of infection. Skin exposures to the urticating hairs can be treated by applying and then pulling off some sticky tape such as duct tape, which carries the hairs off with it. If any breathing difficulty or chest pain occurs, go to a hospital as this may indicate an anaphylactic reaction. As with bee stings, the allergic reaction may be many times more dangerous than the toxic effects of the venom.
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