For other uses, see: Tarantula (disambiguation)
Grammostola species tarantula
Tarantulas are spiders belonging to the family Theraphosidae. They are characterized by having tarsi (feet) with two claws and claw tufts, called scopulae.
The word tarantula applies to two very different kinds of spider. The spider that originally got this name is neither particularly large, particularly hairy, nor particularly venomous. Its scientific name is Lycosa tarentula, which makes it one of the wolf spiders. Its name comes from that of Taranto (or Tarentum in Latin), a town in Southern Italy. The bite of this spider was once believed to cause a fatal condition called tarantism. The cure for the disease was believed to involve wild dancing of a kind that has come to be called the tarantella. Actually, the bite of this kind of spider is not even particularly painful, let alone life-threatening. There appears to have been an entirely different kind of spider in the fields around Taranto that caused fairly severe bites (one candidate being the malmignatte or Mediterranean black widow, one of several species in the genus Latrodectus), but the tarantulas, being wolf spiders, were fairly large, out in the open, and were frequently seen running around, which drew attention to them, and so they got the blame. Join that factor with the belief in tarantism and the supposed need for wild dancing to prevent sure death, and the fearsome world-wide reputation of the tarantula was guaranteed.
When people who knew about the tarantulas emigrated to the Americas and discovered fearsomely large and hairy spiders in the New World, they bestowed the name "tarantula" on them. Those spiders belong to the Suborder Mygalomorphae, the Family Theraphosidae ( Greek for thera "wild animal, beast" + phos "light") and the Family Dipluridae. They can be quite large.
Tarantulas can be kept as house pets. A terrarium with an inch or two of damp vermiculite or a mixture of soil and sphagnum moss (but not with cedar shavings as they are toxic to many spiders) on bottom provides an ideal habitat. (Burrowing tarantulas will require a much deeper layer.) Tarantulas can be fed a variety of living animals (insects, small mice, small fish in the water bowl, and reptiles are on their menu).
The true tarantula
The true tarantulas are all spiders of the family Theraphosidae, sometimes called bird spiders, monkey spiders, baboon spiders and rain spiders. 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 111 genera. Tarantulas are excellent climbers.
Tarantulas are long-legged, long-living spiders, whose entire body is covered with short 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, Australia and the Middle East. 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 make 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 are deadly varieties of tarantulas somewhere in South America. 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 spider in the world that is the most highly 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, colour and type
Depending on the species, their body length may vary from 1-3 inches (2.5 - 7.5 cm), with 3 to 5 inch (8-12 cm) leg spans (their size when including their legs). Some species are said to be even larger and to have 10-inch leg spans. On the average, tarantulas weigh from 2 to 3 ounces (60-90 grams). The Goliath birdeater (Theraphosa blondi) 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.
The majority of tarantulas are brown or black, however some species have more extensive colour schemes, 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 more drably colored. 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 stinging hairs, called urticating hairs, on the abdomen, opisthosoma, that they use as a protection against enemies. These hairs are only present on some New World specimens (only the subfamilies of Ischnocolinae, Aviculariinae and Theraphoseae) and are absent on specimens of the Old World.
These fine hairs are barbed and contain a mild venom. 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. Some arboreal species coat their webs with these hairs. Some species do the same thing with their egg cocoons.
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. The symptoms range from species to species, from person to person, from a burning itch to a minor rash. 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).
Tarantulas live in a variety of nests. Burrowing tarantulas live under the ground, in burrows. These burrows are either dug by the spider itself, reused burrows abandoned by rodents or other small creatures, or 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 bark of trees. Still others build silken nests on trees, cliff faces, the walls of buildings or in plants such as bananas and pineapples.
Growth, life, and mating
To grow, tarantulas, like other spiders, have to shed their exoskeleton periodically. This process is 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 take 2 to 5 years to mature into adults, but some species take up to 10 years to reach maturity. Upon reaching adulthood, males have only a short time remaining in their lives, about one year to a year and a half - they will immediately go in search of a female to mate with. Once the male is a mature adult, it will most likely never moult again before dying.
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 vibrate and tap her legs also. 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.
Females will continue to molt after reaching maturity and because of this are able to regenerate lost limbs and have a longer life. Female specimens have been known to reach 30 years of age or even 40 years, and have survived on water alone for up to 2.5 years. On the average, females live 20-30 years and males 10-12 years, depending on species, if well cared for.
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 guards 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.
A nocturnal predator
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. 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.
Bites and treatment
There are no substantiated reports of tarantula bites proving fatal to a human. However, 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. If there are indeed deadly tarantulas of some kind, it may simply be the case that 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. 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 abdomen into the air, lifting their front legs into the air, spreading and retracting their fangs, and making a loud hissing noise by rubbing their fangs together. 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: 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.
Turning the tables
On one of their TV specials, National Geographic illustrated the methods used by some Amazonian peoples to hunt and cook tarantulas. A tarantula was captured by holding it down with a stick and its legs were then bent upward and bound. The hapless creature was then roasted alive in a folded leaf. Being a cousin to shellfish, the taste of its meat is said to resemble that of shrimp. The Goliath birdeater tarantula (Theraphosa Blondi) is considered a delicacy by the indigenous Piaroa of Venezuela.