Mexican red-knee tarantulas are preyed upon by birds, moths, lizards, and other insectivores. When threatened by large predators, Mexican red-knee tarantulas can flick or drop hairs off of their abdomen. These "urticating" hairs are barbed and dig into the skin, causing irritation or a painful rash. If the hairs penetrate an organism's eyes, they can cause blindness.
Known Predators:
Mexican red-knee tarantulas are large, dark spiders that range from 12.7 to 14 cm in length. They have a black abdomen that is covered in brown hairs. Their legs have orange to dark red-orange joints, giving them their name. Their carapace is creamy beige in color and has a distinctive black square. The cephalothorax has four pairs of legs, a pair of pedipalps, and hollow fanged chelicerae connected to venom glands. They hold and catch prey with the first 2 legs and walk with the other legs. There are 2 pairs of spinnerets on the posterior side of their abdomen. Adult males have special copulatory organs located on their pedipalps. Females are generally larger than males.
Range length: 12.7 to 14 cm.
Other Physical Features: ectothermic ; heterothermic ; bilateral symmetry ; venomous
Sexual Dimorphism: female larger
Female Mexican red-knee tarantulas typically live 25 to 30 years while males rarely live more than 10 years.
Typical lifespan
Status: wild: male 10 years; female 30 (high) years.
Mexican red-knee tarantulas reside in dry areas with little vegetation, usually in scrubland, deserts, dry thorn forests, or tropical deciduous forests. They live in burrows in rocky areas at the base of thorny vegetation like cacti. Burrows usually have one entrance that is a little wider than the tarantula itself. A web carpet extends from the burrow out of the opening but is usually covered or coated in the substrate of the area. When the burrow is in use, silk can be found near the entrance. During the reproductive season, extra silk is present in the burrows of mature females.
Habitat Regions: tropical ; terrestrial
Terrestrial Biomes: rainforest ; scrub forest
Mexican red-knee tarantulas have eight eyes located around their head so they can see both forward and backward. However, their vision is relatively poor. Hairs on their legs are used to sense vibrations, and the palps on the end of their legs allow them to smell, taste, and feel. Each foot has two claws, enabling the spider to climb slippery surfaces.
Communication Channels: visual ; tactile
Other Communication Modes: vibrations
Perception Channels: visual ; vibrations ; chemical
Mexican red-knee spiders are considered "near threatened" by the IUCN and are on Apendex II of CITES, which limits trade of individuals between countries. It is illegal to catch and sell wild individuals. Mexican red-knee spiders are at risk because of the pet trade and habitat destruction.
US Federal List: no special status
CITES: appendix ii
IUCN Red List of Threatened Species: lower risk - near threatened
Mexican red-knee tarantulas, like many tarantulas, grow slowly. Females wrap fertilized eggs in silk and carry the egg-sac between her fangs. After 1 to 3 months, the eggs hatch. Spiderlings molt every 2 weeks for the first 4 months, and less frequently after that. Males do not molt after reaching sexual maturity at 4 to 5 years of age. Females, though infrequently, continue to molt after reaching sexual maturity at 6 to 7 years of age. Molting removes any external parasites or fungus and provides new undamaged sensory and protective hairs.
Mexican red-knee tarantulas are generally docile and do not harm humans. However, when threatened, they can shoot their urticating hairs for defense, which can cause irritation. Their bite, while venomous, is not fatal and can cause pain equivalent to a bee or wasp sting. Some individuals are allergic to spider venom and have more severe reactions.
Negative Impacts: injures humans (bites or stings, venomous )
Because they are docile and colorful, Mexican red-knee tarantulas are popular in the pet trade, generating considerable income. They are also kept in many zoological institutions. Mexican red-knee tarantulas are commonly used in Hollywood films, as well.
Positive Impacts: pet trade
As generalists, Mexican red-knee tarantulas do not control species of prey. As a whole, however, tarantulas help stabilize or regulate insect populations, as tarantulas are one of the biggest families of insectivores and exhibit a wide variety of lifestyles and foraging strategies. Spiders are also important prey for birds, moths, lizards, and other insectivores. Spiders are primary food sources for bark-gathering birds. Birds also use the silk of spiders to build nest, as the protein fibers of their silk adds stability.
Mexican red-knee tarantulas are parasitized by pepsis wasps, which use their body as a nest. Pepsis wasps seek tarantula burrows and vibrate their body, mimicking prey. When a tarantula emerges from its burrow, the wasp stings it and lays eggs in its paralyzed body. When the larvae hatch, they feed upon the tarantula.
Ecosystem Impact: keystone species
Commensal/Parasitic Species:
Mexican red-knee tarantulas prey on large insects, frogs and mice. Mexican red-knee tarantulas remain in their burrow, waiting to ambush prey that walk across their web. Prey are detected using palps on the end of each leg, which are sensitive to smell, taste, and vibrations. Once they detect their prey, Mexican red-knee tarantulas rush out to bite prey and return to the burrow. They hold down their pray with their front legs and inject their venom to paralyze and liquefy their victims. They consume the juices of their prey, leaving behind undigested body parts. These are typically wrapped up in a web and transported to another area of the burrow.
Animal Foods: mammals; amphibians; body fluids; insects
Primary Diet: carnivore (Eats terrestrial vertebrates, Eats body fluids, Insectivore )
Mexican red-knee tarantulas, Brachypelma smithi, are primarily found along the central Pacific coast of Mexico.
Biogeographic Regions: nearctic (Native ); neotropical (Native )
Mexican red-knee tarantulas mate shortly after the male's maturing molt. Before copulation, males weave a special web on which he deposits sperm. Mating occurs near the female's burrow. The male and female face each other, and the female opens her jaws wide. The male uses a special pair of spurs on his front legs to lock her jaws open. They then push each other into a reared-back position. With second set of legs, the male holds the female down and bends her backwards. The male then collects his sperm with his pedipalps and transfers it to the female's opithosoma, a small opening on the underside of the abdomen. The male releases one of the female's fangs, positioning hims legs for retreat. After mating, males generally flee, as females are known to be aggressive to males after mating. Some females may try to kill and eat the male, although this has not been observed in the wild. Mexican red-knee tarantulas are polygynandrous.
Mating System: polygynandrous (promiscuous)
Mexican red-knee tarantulas mate soon after the male's maturing molt, which usually happens between July and October during the rainy season. Females store the sperm and eggs in her body until the spring. Females make a silk mat, on which she lays 200 to 400 eggs, which she covers with a sticky liquid containing the sperm. Fertilization occurs in minutes. The eggs are wrapped in silk and collected into a ball or egg-sac. Females carry the egg-sac between their fangs. Eggs hatch in 1 to 3 months, though spiderlings remain in the egg-sac for another 3 weeks after hatching. After leaving the egg-sac, spiderlings spend another 2 weeks in their burrow before they disperse. They reach independence at this point, usually at 12 to 16 days of age. Males reach sexual maturity at approximately the 20th instar (the stage between molts that comes at about 4 years of age). Females mature 2 to 3 years later than males, at 6 to 7 years of age. In captivity, Mexican red-knee tarantulas mature more quickly than in the wild.
Breeding season: Mexican red-knee tarantulas typically mate between July and October, usually in the rainy season.
Range number of offspring: 200 to 400.
Average gestation period: 9 weeks.
Range time to independence: 12 to 16 days.
Range age at sexual or reproductive maturity (female): 6 to 7 years.
Average age at sexual or reproductive maturity (male): 4 years.
Key Reproductive Features: seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization (Internal ); oviparous
Female Mexican red-knee tarantulas wrap their eggs in a silk egg-sac and carry them between their fangs. Egg-sacs may also be placed in hollows between or beneath rocks or natural debris. A female guards her egg-sac, turns it, and moves it around to ensure appropriate humidity and temperature are maintained. Eggs hatch in approximately 9 weeks, though spiderlings remain in the egg-sac for another 3 weeks. After emerging from the egg-sac, they remain in the burrow with their mother for an additional 2 weeks. Mothers guard their offspring until they disperse around 12 to 16 days of age.
Parental Investment: precocial ; female parental care ; pre-hatching/birth (Protecting: Female); pre-independence (Protecting: Female)
Brachypelma smithi is a species of spider in the family Theraphosidae (tarantulas) native to Mexico.[3] It has been confused with Brachypelma hamorii; both have been called Mexican redknee tarantulas.[4] Mexican redknee tarantulas are a popular choice as pets among tarantula keepers. Many earlier sources referring to B. smithi either relate to B. hamorii or do not distinguish between the two species. B. smithi is a terrestrial tarantula native to Pacific coast of the Mexican state of Guerrero.[4]
Brachypelma smithi is a large spider. A sample of seven females had a total body length (excluding chelicerae and spinnerets) in the range 52–59 mm (2.0–2.3 in). A sample of eight males were slightly smaller, with a total body length in the range 44–49 mm (1.7–1.9 in). Although males have slightly shorter bodies, they have longer legs. The fourth leg is the longest, measuring 70 mm (2.8 in) in the type male and 66 mm (2.6 in) in a female. The legs and palps are bluish black with three distinctly colored rings: dark reddish orange on the part of the patellae closest to the body with light yellowish pink further away, pale yellowish pink on the lower part of the tibiae, and pinkish white at the end of the metatarsi. Adult males have a yellowish brown carapace; the upper surface of the abdomen is black. Adult females vary more in carapace color and pattern. The carapace may be mainly bluish black with a light brown border, or the dark area may be broken up into a "starburst" pattern or almost reduced to two dark patches in the eye area.[4]
The species was first described by Frederick Pickard-Cambridge in 1897 as Eurypelma smithi.[3] It was collected at Dos Arroyos, Guerrero, Mexico, by H. H. Smith.[5] It was transferred to the genus Brachypelma by Reginald Pocock in 1903.[3] Pickard-Cambridge identified the type specimen as a female, but in 1968 it was noticed that it was actually an immature male. In 1994, A. M. Smith confirmed that the holotype was an immature male, and redescribed the species using two different specimens: an adult male and an adult female. The specimens he used cannot now be found, but his description makes it clear that they actually belonged to a different species, B. hamorii. Even prior to Smith's description, B. hamorii had been misidentified as B. smithi.[4]
The two species have very similar colour patterns. When viewed from above, the chelicerae of B. hamorii have two brownish pink bands on a greyish background, not visible on all individuals. B. smithi lacks these bands. Mature males of the two species can be distinguished by the shape of the palpal bulb. That of B. smithi is straighter with a broad spoon shape when viewed retrolaterally and a wider keel at the apex. In mature females of B. smithi the baseplate of the spermatheca is divided and subtriangular, rather than elliptical as in B. hamorii; also the ventral face of the spermatheca is striated rather than smooth.[4]
Brachypelma annitha was described as a separate species in 1997, but is now considered to be conspecific with B. smithi.[3][4]
DNA barcoding has been applied to some Mexican species of Brachypelma. In this approach, a portion of about 650 base pairs of the mitochondrial gene cytochrome oxidase I (COI) is used, primarily to identify existing species, but also sometimes to support a separation between species. In 2017, Mendoza and Francke showed that although B. smithi and B. hamorii are similar in superficial external appearance, they are clearly distinguished both by some finer aspects of morphology and by their DNA barcodes, although the supposed species B. annitha is nested within B. smithii.[4]
Brachypelma smithi and the very similar B. hamorii are found along the Pacific coast of Mexico on opposite sides of the Balsas River basin as it opens onto the Pacific. B. smithi is found to the south, in the state of Guerrero. The natural habitat of the species is in hilly deciduous tropical forests. It constructs or extends burrows under rocks and tree roots, among dense thickets and deciduous forests.[4]
The burrows were described in 1999 by a source which did not distinguish between Brachypelma hamorii and B. smithi. The deep burrows keep them protected from predators, like the white-nosed coati, and enable them to ambush passing prey, such as large insects, frogs and mice.[6] The females spend the majority of their lives in their burrows. The burrows are typically located in or not far from vegetation and consist of a single entrance with a tunnel leading to one or two chambers. The entrance is just slightly larger than the body size of the spider. The tunnel, usually about three times the tarantula's leg span in length, leads to a chamber which is large enough for the spider to safely molt. Further down the burrow, via a shorter tunnel, a larger chamber is located where the spider rests and eats its prey. When the tarantula needs privacy, e.g. when molting or laying eggs, the entrance is sealed with silk, sometimes supplemented with soil and leaves.[7]
In 1985, B. smithi (then not distinguished from B. hamorii) was placed on CITES Appendix II, and in 1994, all remaining Brachypelma species were added.[8] Large numbers of Mexican redknee tarantulas caught in the wild continue to be smuggled out of Mexico. It is reported that at least 3,000 specimens of Mexican tarantulas were sent to the United States or Europe a few years prior to 2017, most of which were Mexican redknee tarantulas.[4]
Brachypelma smithi is a species of spider in the family Theraphosidae (tarantulas) native to Mexico. It has been confused with Brachypelma hamorii; both have been called Mexican redknee tarantulas. Mexican redknee tarantulas are a popular choice as pets among tarantula keepers. Many earlier sources referring to B. smithi either relate to B. hamorii or do not distinguish between the two species. B. smithi is a terrestrial tarantula native to Pacific coast of the Mexican state of Guerrero.
