Tarantula & Scorpion WebQuest



Scorpions are eight-legged arthropods. A member of the Arachnida class and belonging to the order Scorpiones, there are about 2000 species of scorpions. They are found widely distributed south of 49° N, except New Zealand and Antarctica. The northern-most part of the world where scorpions live in the wild is Sheerness on the Isle of Sheppey in the UK, where a small colony of Euscorpius flavicaudis has been resident since the 1860s.


The cuticle makes a tough armor around the body. In some places it is covered with hairs that act like balance organs. An outer layer that makes them fluorescent green under ultraviolet light is called the hyaline layer. Newly molted scorpions do not glow until after their cuticle has hardened. The fluoresent hyaline layer can be intact in fossil rocks that are hundreds of millions of years old.

The body of a scorpion is divided into two segments: the cephalothorax (also called the prosoma) and the abdomen/opisthosoma. The abdomen consists of the mesosoma and the metasoma.

  A.   Cephalothorax

The cephalothorax, also called prosoma, is the scorpion's “head”, comprising the carapace, eyes, chelicerae (mouth parts), pedipalps (claw) and four pairs of walking legs.

  B.   Mesosoma

The mesosoma, the abdomen's front half, is made up of six segments. The first segment contains the sexual organs as well as a pair of vestigial and modified appendages forming a structure called the genital operculum. The second segment bears a pair of featherlike sensory organs known as the pectines; the final four segments each contain a pair of book lungs. The mesosoma is armored with chitinous plates, known as tergites on the upper surface and sternites on the lower surface.

  C.   Metasoma

The metasoma, the scorpion's tail, comprising six segments (the first tail segment looks like a last mesosoman segment), the last containing the scorpion's anus and bearing the telson (the sting). The telson, in turn, consists of the vesicle, which holds a pair of venom glands and the hypodermic aculeus, the venom-injecting barb.

On rare occasions, scorpions can be born with two metasomata (tails). Two-tailed scorpions are not a different species, but rather a genetic abnormality.




Most scorpions reproduce sexually and most species have male and female individuals. While the majority of scorpion species reproduce sexually, some, such as Hottentotta hottentotta, Liocheles australasiae, Tityus columbianus, Tityus metuendus, Tityus serrulatus, Tityus stigmurus, Tityus trivittatus, and Tityus urugayensis, all reproduce through parthenogenesis, a process in which unfertilized eggs develop into living embryos. Parthenogenic reproduction starts following the scorpion's final moult to maturity and continues thereafter. Sexual reproduction is accomplished by the transfer of a spermatophore from the male to the female; scorpions possess a complex courtship and mating ritual to effect this transfer. Mating starts with the male and female locating and identifying each other using a mixture of pheromones and vibrational communication; once they have satisfied each other that they are of opposite sex and of the correct species, mating can commence.

The courtship starts with the male grasping the female’s pedipalps with his own; the pair then performs a "dance" called the "promenade à deux". In reality this is the male leading the female around searching for a suitable place to deposit his spermatophore. The courtship ritual can involve several other behaviours such as juddering and a cheliceral kiss, in which the male's chelicerae--clawlike mouthparts--grasp the female's in a smaller more intimate version of the male's grasping the female's pedipalps and in some cases injecting a small amount of his venom into her pedipalp or on the edge of her cephalothorax, probably as a means of pacifying the female.

When he has identified a suitable location, he deposits the spermatophore and then guides the female over it. This allows the spermatophore to enter her genital opercula, which triggers release of the sperm, thus fertilizing the female. The mating process can take from 1 to 25+ hours and depends on the ability of the male to find a suitable place to deposit his spermatophore. If mating goes on for too long, the female may eventually break off the process.

Once the mating is complete, the male and female quickly separate. The male will generally retreat quickly, most likely to avoid being cannibalized by the female, although sexual cannibalism is infrequent with scorpions.

Birth and development

Compsobuthus werneri female with young

Compsobuthus werneri female with young



Unlike the majority of Arachnida species, scorpions are viviparous. The young are born one by one, and the brood is carried about on its mother's back until the young have undergone at least one moult. Before the first moult, scorplings cannot survive naturally without the mother, depending on her for protection and to regulate their moisture levels. Especially in species which display more advanced sociability (e.g Pandinus spp.), the young/mother association can continue for an extended period of time. The size of the litter depends on the species and environmental factors, and can range from two to over a hundred scorplings.


The young generally resemble their parents. Growth is accomplished by periodic shedding of the exoskeleton (ecdysis). A scorpion's developmental progress is measured in instars (how many moults it has undergone). Scorpions typically require between five and seven moults to reach maturity. Moulting is effected by means of a split in the old exoskeleton which takes place just below the edge of the carapace (at the front of the prosoma). The scorpion then emerges from this split; the pedipalps and legs are first removed from the old exoskeleton, followed eventually by the metasoma. When it emerges, the scorpion’s new exoskeleton is soft, making the scorpion highly vulnerable to attack. The scorpion must constantly stretch while the new exoskeleton hardens to ensure that it can move when the hardening is complete. The process of hardening is called sclerotization. The new exoskeleton does not fluoresce; as sclerotization occurs, the fluorescence gradually returns.

Life and habits

Scorpions have quite variable lifespans and the actual lifespan of most species is not known. The age range appears to be approximately 4-25 years (25 years being the maximum reported life span in the species H. arizonensis).Lifespan of Hadogenes species in wild is estimated to 25-30 years.

Scorpions prefer to live in areas where the temperatures range from 20°C to 37°C (68°F to 99°F), but may survive from freezing temperatures to the desert heat.

Scorpions of genus Scorpiops living in hight Asian mounties,Bothriuridae scorpions from Patagonia and smal Euscorpius scorpions from middle Europe in Winter survives temperatures about -25°C.

They are nocturnal and fossorial, finding shelter during the day in the relative cool of underground holes or undersides of rocks and coming out at night to hunt and feed. Scorpions exhibit photophobic behavior, primarily to evade destruction by their predators such as birds, centipedes, lizards, mice, possums, and rats.


Scorpions are opportunistic predators of small arthropods and insects. They use their chela (pincers) to catch the prey initially. Depending on the toxicity of their venom and size of their claws, they will then either crush the prey or inject it with neurotoxic venom. This will kill or paralyze the prey so the scorpion can eat it. Scorpions have a relatively unique style of eating using chelicerae, small claw-like structures that protrude from the mouth that are found only in a handful of invertebrates, including spiders and vinegaroons. The chelicerae, which are very sharp, are used to pull small amounts of food off the prey item for digestion. Scorpions can only digest food in a liquid form; any solid matter (fur, exoskeleton, etc) is disposed of by the scorpion.


All scorpion species possess venom. In general, scorpion venom is described as neurotoxic in nature. One exception to this however is Hemiscorpius lepturus which possesses cytotoxic venom. The neurotoxins consist of a variety of small proteins as well as sodium and potassium cations, which serve to interfere with neurotransmission in the victim which causes paralysis without damage to the tissues. Scorpions use their venom to kill or paralyze their prey so that it can be eaten; in general it is fast acting, allowing for effective prey capture. The effects of the sting can be severe.

Scorpion venoms are optimized for action upon other arthropods and therefore most scorpions are relatively harmless to humans; stings produce only local effects (such as pain, numbness or swelling). A few scorpion species, however, mostly in the family Buthidae, can be dangerous to humans. Among the most dangerous are Leiurus quinquestriatus, otherwise dubiously known as the deathstalker, which has the most potent venom in the family, and members of the genera Parabuthus, Tityus, Centruroides, and especially Androctonus, which also have powerful venom. The scorpion which is responsible for the most human deaths is Androctonus australis, or the yellow fat-tailed scorpion of North Africa. The toxicity of A. australis's venom is roughly half that of L. quinquestriatus, but despite the common misconception A. australis does not inject noticeably more venom into its prey. The higher death count is simply due to its being found more commonly, especially near humans. Human deaths normally occur in the young, elderly, or infirm; scorpions are generally unable to deliver enough venom to kill healthy adults. Some people, however, may be allergic to the venom of some species. Depending on the severity of the allergy, the scorpion's sting may cause anaphylaxis and death. A primary symptom of a scorpion sting is numbing at the injection site, sometimes lasting for several days. Scorpions are generally harmless and timid, and only voluntarily use their sting for killing prey, defending themselves or in territorial disputes with other scorpions. Generally, they will run from danger or remain still.

It should be noted that the family Buthidae, while containing perhaps the highest number of dangerous species, also contains many species that are not thought to be medically significant.

Scorpions are able to regulate how much venom is injected with each sting using striated muscles in the stinger, the usual amount being between 0.1 and 0.6 mg. There is also evidence to suggest that scorpions restrict the use of their venom using it only to subdue large prey, or prey that struggles. It has been found that scorpions have two types of venom: a translucent, weaker venom designed to stun only, and an opaque, more potent venom designed to kill heavier threats. This is likely because it is expensive in terms of energy for a scorpion to produce venom, and because it may take several days for a scorpion to replenish its venom supply once it has been exhausted.

There is currently no equivalent of the Schmidt Sting Pain Index because nobody has yet classified the levels of pain inflicted by different scorpion stings. This is probably because of the risk involved with some species, such as Androctonus australis or Leiurus quinquestriatus. However, envenomation by a mildly venomous species like Pandinus imperator is similar to a bee sting in terms of the pain and swelling that results. A sting on the thumb from a relatively non-dangerous scorpion often feels like the victim has accidentally struck their thumb with a hammer whilst driving in a nail. A sting on the thumb from a truly dangerous scorpion can feel much worse, as though the victim had hammered a nail right through their thumb. It should be noted that the physical effects of a sting from a medically significant scorpion are not limited to the pain inflicted: there can be bradycardia, tachycardia or in severe cases pulmonary edema.

The stings of North American scorpions are rarely serious and usually result in pain, minimal swelling, tenderness, and warmth at the sting site. However, the Arizona bark scorpion (Centruroides exilicauda or sculpturatus), which is found in Arizona and New Mexico and on the California side of the Colorado River, has a much more toxic sting. The sting is painful, sometimes causing numbness or tingling in the area around the sting. Serious symptoms are more common in children and include abnormal head, eye, and neck movements; increased saliva production; sweating; and restlessness. Some people develop severe involuntary twitching and jerking of muscles. Breathing difficulties may occur. The stings of most North American scorpions require no special treatment. Placing an ice cube on the wound reduces pain, as does an ointment containing a combination of an antihistamine, an analgesic, and a corticosteroid. Centruroides stings that result in serious symptoms may require the use of sedatives, such as midazolam, given intravenously. Centruroides antivenom rapidly relieves symptoms, but it may cause a serious allergic reaction or serum sickness. The antivenom is available only in Arizona . In Trinidad the leaf juice of Eclipta prostrata is used for scorpion stings. Any effect of plants that are used against scorpion stings may be due to symptomatic relief – analgesic, antiinflammatory, antipruritic effects, in addition to other biological activities. Some compounds from plants used for general inflammation also inhibit enzymes (like phospholipase A2) from snake and scorpion venom. Some of these plant compounds are hypolaetin-8-glucoside and related flavanoids.

Professor Moshe Gueron was the first to investigate the Cardiovascular Manifestations Affect of Severe Scorpion Sting.  Thousands of stung patients were reviewed. Thirty-four patients with severe scorpion sting were reviewed and pertinent data related to the cardiovascular system such as hypertension, peripheral vascular collapse, congestive heart failure or pulmonary edema were analyzed. The electrocardiograms of 28 patients were reviewed; 14 patients showed "early myocardial infarction-like" pattern. The urinary catecholamine metabolites were investigated in 12 patients with scorpion sting. Vanylmandelic acid was elevated in seven patients and the total free epinephrine and norepinephrine in eight. Six of these 12 patients displayed the electrocardiographic "myocardial infarction-like" pattern. Nine patients died and the pathologic lesions of the myocardium were reviewed in seven. Also, Gueron reported five cases of Severe Myocardial damage and heart failure in Scorpion sting from Beer-Sheba, Israel. He described hypertension, pulmonary oedema with hypertension, hypotension, pulmonary oedema with hypotension and rhythm disturbances as five different syndromes that may dominate the clinical picture in scorpion sting victim. He suggested that all patients with cardiac symptoms should be admitted to an intensive cardiac unit. A few years later, at 1990, he was reported poor contractility with low ejection fraction, decreased systolic left ventricular performance, lowered fractional percentage shortening observed in echocardiographic and radionuclide angiographic study. Gueron was questioned regarding the value of giving antivenom, and he replied that although is freely available, all cases of scorpion sting are treated without it, and there had not been a single fatality in 1989.

Fossil record

Scorpions have been found in many fossil records, including coal deposits from the Carboniferous Period and in marine Silurian deposits. They are thought to have existed in some form since about 425–450 million years ago. They are believed to have an oceanic origin, with gills and a claw-like appendage that enabled them to hold onto rocky shores or seaweed.

The eurypterids, marine creatures which lived during the Paleozoic era, share several physical traits with scorpions and are closely related to them. Various species of Eurypterida could grow to be anywhere from 10 cm (4 in) to 3 m (9.75 ft) in length. However, they exhibit anatomical differences marking them off as a group distinct from their Carboniferous and recent descendants. Despite this, some refer to them as "sea scorpions." Their legs are thought to have been short, thick, tapering and to have ended in a single strong claw; it appears that they were well-adapted for maintaining a secure hold upon rocks or seaweed against the wash of waves, like the legs of shore-crab.

Geographical distribution

Hadrurus spadix - Caraboctonidae, Hadrurinae

Hadrurus spadix - Caraboctonidae, Hadrurinae

Scorpions are almost universally distributed south of 49° N, and their geographical distribution shows in many particulars a close and interesting correspondence with that of the mammals, including their entire absence from New Zealand. The facts of their distribution are in keeping with the hypothesis that the order originated in the northern hemisphere and migrated southwards into the southern continent at various epochs, their absence from the countries to the north of the above-mentioned latitudes being due, no doubt, to the comparatively recent glaciation of those areas. When they reached Africa, Madagascar was part of that continent; but their arrival in Australia was subsequent to the separation of New Zealand from the Austro-Malayan area to the north of it.

In the United States , scorpions are most common in southern
Arizona and in a swath of land extending through central Texas and central Oklahoma. The common striped scorpion, Centruroides vittatus, reaches from northwest Mexico to southern Colorado, Kansas, southern Missouri, and Mississippi and Louisiana. Species of the genus Vaejovis are found from Florida north to Maryland, the Carolinas, and Tennessee, and as far west as Oregon and California. Paruroctonus boreus is found through the Northwest U.S. and into Canada (Southern Saskatchewan, Southern Alberta and the Okanagan Valley of British Columbia). Scorpions can be found in 31 different states in the U.S. , including Hawaii (Isometrus maculatus).

Five colonies of scorpions (Euscorpius flavicaudis) have established themselves in southern England having probably arrived with imported fruit from Africa, but the number of colonies could be lower now because of the destruction of their habitats. This scorpion species is small and completely harmless to humans.

Suicide misconception

The belief that scorpions commit suicide by stinging themselves to death when surrounded by fire is of considerable antiquity and is often prevalent where these animals exist. It is nevertheless untrue since the venom has no effect on the scorpion itself, nor on any member of the same species (unless the venom is injected directly into the scorpion's nerve ganglion—quite an unlikely event outside of the laboratory). The misconception may derive from the fact that scorpions are poikilotherms (cold-blooded): when exposed to intense heat their metabolic processes malfunction. This causes the scorpion to spasm wildly and this spasming may appear as if the scorpion is stinging itself. It is also untrue that alcohol will cause scorpions to sting themselves to death.

Ultraviolet light

A scorpion under a blacklight.  In normal lighting this scorpion appears black.

A scorpion under a blacklight. In normal lighting this scorpion appears black.

Scorpions are also known to glow when exposed to certain wavelengths of ultraviolet light such as that produced by a blacklight.






Tarantula is the common name for a group of "hairy" and often very large spiders belonging to the familyTheraphosidae, of which approximately 900 species have been identified. Tarantulas hunt prey in both trees and on the ground. All tarantulas can emit silk, whether they be arboreal or terrestrial species. Arboreal species will typically reside in a silken "tube web", and terrestrial species will line their burrows or lairs with web to catch wandering prey. They mainly eat insects and other arthropods, using ambush as their primary method. The biggest tarantulas can kill animals as large as lizards, mice, or birds. Most tarantulas are harmless to humans, and some species are popular in the exotic pet trade while others are eaten as food. These spiders are found in tropical and desert regions around the world.

The name tarantula comes from the town of Taranto in Southern Italy and was originally used for an unrelated species of either European wolf spider (See Lycosa tarantula for more information about this spider the appearance of which resembles that of that tarantula family) or the Mediterranean black widow (the effects of whose bite more closely resemble that described in Taranto). In Africa , Theraphosids are frequently referred to as "baboon spiders". Asian forms are known as "earth tigers" or "bird spiders". Australians refer to their species as "barking spiders", "whistling spiders," or "bird spiders". People in other parts of the world also apply the general name "mygales" to Theraphosid spiders.

There are other species also referred to as tarantulas outside this family; the evolution of the name Tarantula is discussed below. This article primarily concerns the Theraphosids.


Like all arthropods, the tarantula is an invertebrate that relies on an exoskeleton for muscular support. A tarantula’s body consists of two main parts, the prosoma or the cephalothorax (the former is most often used because there is no analogous "head") and the abdomen or opisthosoma. The prosoma and opisthosoma are connected by the pedicle or what is often called the pregenital somite. This waist-like connecting piece is actually part of the prosoma and allows the opisthosoma to move in a wide range of motion relative to that of the prosom.

Depending on the species, the body length of tarantulas range from 2.5 - 10 cm (1-4 inches), with 8-30 cm (3 to 12 inch) leg spans (their size when including their legs). Legspan is determined by measuring from the tip of the back leg to the tip of the front leg on the same side, although some people measure from the tip of the first leg to the tip of the fourth leg on the other side. The largest species of tarantulas can weigh over 9 grams (0.3 ounces). One candidate for the title of the largest of all species, the Theraphosa blondi (goliath birdeater) from Venezuela and Brazil has been reported to have a weight of 3 ounces and a leg span of up to 13 inches (33 cm). The males have the long length, and the females have lots of girth.

Theraphosa apophysis (the pinkfoot goliath) was described 187 years after the Goliath birdeater; therefore its characteristics are not as well attested. However, legspans of up to 33 cm (13 inches) have been reported for that species. T. blondi is generally thought to be the heaviest tarantula, and T. apophysis the largest legspan. Two other species, Lasiodora parahybana and Lasiodora klugi, (the Brazilian salmon birdeater) gets very large and rivals the size of both Theraphosa blondi and Theraphosa apophysis, and some have even made claims to same size and even bigger sizes than the two Theraphosa species.

The majority of North American tarantulas are brown. Many species have more extensive coloration patterns, ranging from cobalt blue (Haplopelma lividum), black with white stripes (Eupalaestrus campestratus or Aphonopelma seemanni), to metallic blue legs with vibrant orange abdomen (Chromatopelma cyaneopubescens, green bottle blue). 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 that build tented shelters well off the ground.


Sub-adult Female Poecilotheria regalis

Sub-adult Female Poecilotheria regalis

The eight legs, the two chelicerae with their fangs, and the pedipalps are attached to the prosoma. The chelicerae are two single segment appendages that are located just below the eyes and directly forward of the mouth. The chelicerae contain the venom glands that vent through the fangs. The fangs are hollow extensions of the chelicerae that inject venom into prey or animals that the tarantula bites in defense, and they are also used to masticate. These fangs are articulated so that they can extend downward and outward in preparation to bite or can fold back toward the chelicerae as a butchers knife blade folds back into its handle. The chelicerae of tarantulas completely contain the venom glands and the muscles that surround them and can cause the venom to be forcefully injected into prey.

The pedipalps are two six–segment appendages connected to the thorax near the mouth and protruding on either side of both chelicerae. In most species of tarantula, the pedipalps contain sharp jagged plates used to cut and crush food often called the coxae or maxillae.  As with other spiders, the terminal portion of the pedipalps of males function as part of its reproductive system. Male spiders spin a silken platform (sperm web) on the ground onto which they release semen from glands in their opistoma. Then they insert their pedipalps into the semen, absorb the semen into the pedipalps, and later insert the pedipalps (one at a time) into the reproductive organ of the female, which is located in her abdomen. The terminal segments of the pedipalps of male tarantulas are larger in circumference than those of a female tarantula.

A tarantula has 4 pairs of legs but 8 pairs of total appendages. Each leg has seven segments which from the prosoma out are: coxa, trochanter, femur, patella, tibia, tarsus and pretarsus, and claw. Two or three retractable claws are at the end of each leg. These claws are used to grip surfaces for climbing. Also on the end of each leg, surrounding the claws, is a group of hairs. These hairs, called the scopula, help the tarantula to grip better when climbing surfaces like glass. The fifth pair are the pedipalps which aid in feeling, gripping prey, and mating for a mature male. The sixth pair of appendages are the fangs.

The seventh and eighth pairs of appendages are the four spinnerettes, which also are hypothesized by some to have been leglike appendages. When walking, a tarantula's first and third leg on one side move at the same time as the second and fourth legs on the other side of his body. The muscles in a tarantula's legs cause the legs to bend at the joints, but to extend a leg, the tarantula increases the pressure of blood entering the leg.

Tarantulas, like almost all other spiders, have their spinnerets at the end of the opisthosoma. Unlike spiders that on average have six, tarantulas have two or four spinnerets. Spinnerets are flexible tubelike structures from which the spider exudes its silk. The tip of each spinneret is called the spinning field. Each spinning field is covered by as many as one hundred spinning tubes through which silk is produced. This silk hardens on contact with the air to become a thread like substance.

Digestive system

The tarantula’s mouth is located under its chelicerae on the lower front part of its prosoma. The mouth is a short straw-shaped opening which can only suck, meaning that anything taken into it must be in liquid form. Prey with large amounts of solid parts such as mice must be crushed and ground up or predigested, which is accomplished by spraying the prey with digestive juices that are excreted from openings in the chelicerae.

The tarantula’s digestive organ (stomach) is a tube that runs the length of its body. In the prosoma, this tube is wider and forms the sucking stomach. When the sucking stomach's powerful muscles contract, the stomach is increased in cross-section, creating a strong sucking action that permits the tarantula to suck its liquified prey up through the mouth and into the intestines. Once the liquified food enters the intestines, it is broken down into particles small enough to pass through the intestine walls into the haemolymph (blood stream) where it is distributed throughout the body.

Nervous system

closeup of a tarantula's eye

C loseup of a tarantula's eye

A tarantula's central nervous system (brain) is located in the bottom of the inner prosoma. The central nervous system controls all of the body's activities. A tarantula maintains awareness of its surroundings by using its sensory organs, setae. Although it has eyes, a tarantula’s sense of touch is its keenest sense and it often uses vibrations given off by its prey's movements to hunt. A tarantula's setae are very sensitive organs and are used to sense chemical signatures, vibration, wind direction and possibly even sound. Tarantulas are also very responsive to the presence of certain chemicals such as pheromones.

The eyes are located above the chelicerae on the forward part of the prosoma. They are small and usually set in two rows of four. Most tarantulas are not able to see much more than light, darkness, and motion. Arboreal tarantulas see better than terrestrial tarantulas.

Respiratory system

In all types of tarantulas there are two book lungs (breathing organs). The book lungs are located in a cavity inside the lower front part of the abdomen near where the abdomen connects to the cephalothorax. Air enters the cavity through a tiny slit on each side of and near the front of the abdomen. Each lung consists of 15 or more thin sheets of folded tissue arranged like the pages of a book. These sheets of tissue are supplied by blood vessels. As air enters each lung, oxygen is taken into the blood stream through the blood vessels in the lungs. Needed moisture may also be absorbed from humid air by these organs.

Circulatory system

A tarantula’s blood is unique; an oxygen-transporting protein is present (the copper-based hemocyanin) but not enclosed in blood cells like the erythrocytes of mammals. A tarantula’s blood is not true blood but rather a liquid called haemolymph, or hemolymphy. There are at least four types of hemocytes, or hemolymph cells. The tarantula’s heart is a long slender tube that is located along the top of the opisthosoma. The heart is neurogenic as opposed to myogenic, so nerve cells instead of muscle cells initiate and coordinate the heart. The heart pumps hemolymph to all parts of the body through open passages often referred to as sinuses, and not through a circular system of blood vessels. If the exoskeleton were to be breached, loss of hemolymph could kill the tarantula unless the wound were small enough that the hemolymph could dry and close the wound.

Thermal image of a cold-blooded tarantula on a warm-blooded human hand

Thermal image of a cold-blooded tarantula on a warm-blooded human hand


Besides the normal "hairs" covering the body of tarantulas, some also have a dense covering of irritating hairs called urticating hairs, on the opisthosoma, that they sometimes use as a protection against enemies.  These hairs are only present on New World species and are absent on specimens of the Old World.

These fine hairs are barbed and designed to irritate. They can be lethal to small animals such as rodents. Some people are extremely sensitive to these hairs, and develop serious itching and rashes at the site. Exposure to urticating hairs should be strictly avoided. Species with urticating hairs can kick off these hairs: they are flicked into the air at a target using their back pairs of legs. Tarantulas also use these hairs for other means; using them to mark territory or to line the web or nest (the latter such practice may discourage flies from feeding on the spiderlings). Urticating hairs do not grow back, but are replaced with each molt. The intensity, amount, and flotation of the hairs depends on the species of Tarantula. Many owners of Goliath Bird Eating Spiders (Theraphosa Blondi) claim that Theraphosa's have the worst urticating hairs.

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. In some cases, tarantula hairs have caused permanent damage to human eyes.   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).

Some setae are used to stridulate which makes a hissing sound. These hairs are usually found on the chelicerae. Stridulation seems to be more common in Old World species.


Venomous Bites

Despite their often scary appearance and reputation, none of the true tarantulas are known to have a bite which is deadly to humans. In general 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. 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. 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 (or first) response may also be to whirl suddenly and bite. Tarantulas can be very deceptive in regard to their speed because they habitually move very slowly, but are able to deliver an alarmingly rapid bite when sufficiently motivated.

There are, however, dangerous spiders which are not true tarantulas but which are frequently confused with them. It is a popular urban legend that there exist 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. A likely candidate is the dangerous Brazilian wandering spider (Phoneutria nigriventer), 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 (4-5 inches long), somewhat hairy, highly venomous to humans, and is regarded as aggressive. Another dangerous type of spider confused with tarantulas are the venomous funnel-web tarantulas, which despite their name are not theraphosids. The best known of these is the Sydney funnel-web spider (Atrax robustus), a spider which is aggressive, highly venomous, and prior to the development of antivenom in the 1980s, was responsible for numerous deaths in Australia . These spiders are members of the same suborder as the true tarantulas, but are not found in family Theraphosidae.

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. If this occurs an EpiPen (an autoinjector of epinephrine, also known as adrenaline) should be administered as soon as possible, as complete airway blockage can occur within 20 minutes of exposure to the allergen.

Sexual dimorphism

Some tarantula species exhibit pronounced sexual dimorphism. Males tend to be smaller (especially the abdomen, which can appear quite narrow) and may be quite dull when compared to their female counter parts, as in the species Haplopelma lividum. Mature male tarantulas also have tibial hooks on their front legs, which are used to restrain the female's fangs during copulation.

A juvenile male's sex can be determined by looking at a cast exuvium for exiandrous fusillae or spermathecae. Ventral sexing is less reliable but if done correctly, it can be relatively reliable. Males have much shorter lifespans than females because they die relatively soon after maturing. Few live long enough for a post-ultimate molt. It is unlikely that it happens much in natural habitat because they are vulnerable, but it has happened in captivity rarely. Most males do not live through this molt as they tend to get their emboli, mature male sexual organs on pedipalps, stuck in the molt. Most tarantulas kept as pets are desired to be female. Wild caught tarantulas are often mature males because they wander out in the open and are more likely to be caught while females remain in burrows. A stressed tarantula huddles up in the corner with its legs tucked close to it, does not react, or reacts slowly to touch. A dying tarantula will curl its legs like a clutched hand under it. Its movement is hydraulically motivated and an extended leg takes more energy than a curled one. Tarantulas do not die on their backs unless there is trouble molting.

Excessive dryness can kill tarantulas, especially tropical tarantulas. Although higher humidity helps with molting, it appears that for many tarantulas, humidity does not highly affect molting as much as the actual hydration of the tarantula prior to molting. Most notably though, Theraphosa species must be high in humidity to molt.

Life cycle

the molting process

The molting process

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 as a part of their maturation process, while full grown specimens will only molt once every year or so, or sooner in order to replace lost limbs or lost urticating hairs. A tarantula is obviously going to molt (or "shed, as some call it) when the exoskeleton takes on a darker shade. If a tarantula previously used its urticating hairs, the bald patch will turn from a peach color to deep blue.

Tarantulas may live for 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 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 oldest spider, according to Guinness World Records, lived to be 49 years old

Females will continue to molt after reaching maturity. Female specimens have been known to reach 30 to 40 years of age, and have survived on water alone for up to 2.5 years. Grammostola rosea spiders are renowned for going for long periods without eating.




As with other spiders, the mechanics of intercourse are quite different from those of mammals. Once a male spider reaches maturity and becomes motivated to mate, it will weave a web mat on a flat surface. The spider will then rub its abdomen on the surface of this mat and in so doing release a quantity of semen. It may then insert its pedipalps (short leg-like appendages between the chelicerae and front legs) into the pool of semen. The pedipalps absorb the semen and keep it viable until a mate can be found. When a male spider detects the presence of a female, the two exchange signals to establish that they are of the same species. These signals may also lull the female into a receptive state. If the female is receptive then the male approaches her and inserts his pedipalps into an opening in the lower surface of her abdomen, called the Opithosoma. After the semen has been transferred to the receptive female's body, the male will swiftly leave the scene before the female recovers her appetite. Although females may show some aggression after mating, the male rarely becomes a meal.

Females deposit 50 to 2000 eggs, depending on the species, in a silken egg sac and guard it for 6 to 7 weeks. During this time, the female will stay very close to the eggsac and become more aggressive. The female turns the eggsac often, which is called brooding. This keeps the eggs from deforming due to sitting too long. The young spiderlings remain in the nest for some time after hatching where they live off the remains of their yolk sac before dispersing.

Tarantulas as Pets

Adult Mexican redknee

adult Mexican Redknee

Chilean Rose tarantula

Chilean Rosehair


Tarantulas can be kept as pets and are considered good "apartment pets" by many, being quiet animals, requiring surprisingly little maintenance or cleaning, since unlike snakes and lizards they have no detectable odor. Because of their docile behavior, the species most commonly kept as pets are the Chilean rosehair tarantula (Grammostola rosea), for their price and the Mexican redknee tarantula (Brachypelma smithi), for their beauty. These two species are also some of the easier to care for and are usually easy to handle, while other species (Including most Asian species, such as the cobalt blue tarantula) are more aggressive and shouldn't be handled. Some of the more docile types seem to have a habit of relaxing in people's hands, perhaps attracted by the warmth.

Tarantulas make quite inexpensive pets. Most species can be purchased as juveniles for $20-$50 USD. Adults can be quite expensive as they approach breeding age, and adults of many species can easily reach the several hundred US dollar range. Housing for most species can cost another 40 USD.

A terrarium with an inch or two of damp ground coconut fiber, 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.) Harder substances such as gravel and sand are not suitable for a thriving tarantula; If a tarantula falls too far into a hard surface it can easily injure itself. Sand doesn't hold moisture well and tarantulas are generally prone to dehydration. Ambient temperature and humidity vary by species, with most thriving between 75 degrees and 80°F (24 to 27°C) and between 40% and 80% humidity.

Tarantulas can be fed living animals such as insects, small mice or Pinky Mice, and small fish in the water bowl. A tropical roach colony is a good way to maintain a food supply for a number of tarantulas. The discoid cockroach and death's head cockroach in particular are very easy to care for and will not infest the home if they escape. The death's head cockroaches can be kept in an aquarium with no lid since they cannot climb glass and don't fly. Maintaining a colony of death's head cockroaches only requires keeping them in the dark, feeding them a handful of dog food every couple of weeks and misting them with water every day or two.


Other tarantulas that may make interesting pets are the Brazilian whiteknee tarantula, Chaco golden knee, and Brazilian salmon pink birdeater. These are three of the larger species, each growing over 8 inches with the Brazilian birdeater sometimes reaching 10 inches and considered by many to be the largest species that is docile enough to handle. The foregoing are terrestrial tarantulas, i.e., they generally live in burrows or natural shelters near the ground. Arboreal tarantulas require different housing since, when adult, they make webbed shelters well above ground. Those include Avicularia avicularia and Avicularia metallica, which are generally quite calm and rarely bite. (Any spider will bite if it is being hurt or put in fear for its life.) The arboreal spiders can have large legspans, but their bodies are much less massive than the typical terrestrial tarantulas.

Avicularia metallica, immature female

Avicularia metallica, immature female


The Goliath birdeater tarantula (Theraphosa Blondi) is considered a delicacy by the indigenous Piaroa of Venezuela. Another appearance of the tarantula as food was made on Anthony Bourdain's A Cook's Tour.

 Fried tarantulas are also considered a delicacy in Cambodia.



The word tarantula applies to several very different kinds of spider. The spider originally bearing that name is one of the wolf spiders, Lycosa tarantula, found in the region surrounding the city of Taranto (or Tarentum in Latin), a town in Southern Italy. Compared to true tarantulas, wolf spiders are not particularly large or hairy.

The bite of L. tarantula was once believed to cause a fatal condition called tarantism, whose cure was believed to involve wild dancing of a kind that has come to be identified with the tarantella. However, modern research has shown that the bite of L. tarantula is not dangerous to human beings. There appears to have existed a different species of spider in the fields around Taranto responsible for fairly severe bites. The likely candidate (and the only spider found in the area which is dangerous to man) is the malmignatte or Mediterranean black widow. This spider, which belongs in the genus Latrodectus, is a close relative of the black widow and red-back spiders, and has a bite which is medically significant. However, the so-called tarantulas were fairly large, frequently visible (as is typical of wolf spiders), and thus drew more attention, taking the blame from its relative. These factors, combined with the belief in the fatality of tarantism, assured the other kind of spiders generally called tarantulas a fearsome reputation.

When theraphosidae were encountered by European explorers in the Americas, they were named "tarantulas". Nevertheless, these spiders belong to the suborder Mygalomorphae, and are not at all closely related to wolf spiders.

The name "tarantula" is also applied to other large-bodied spiders, including the purseweb spiders or atypical tarantulas, the funnel-web tarantulas (Dipluridae and Hexathelidae), and the dwarf tarantulas. These spiders are related to true tarantulas (all being mygalomorphs), but are classified in different families. Huntsman spiders of the family Sparassidae are also informally referred to as "tarantulas" because of their large size. They are not related, belonging to the suborder Araneomorphae.