Brachypelma smithi

Geographic Range

Mexican red-knee tarantulas, Brachypelma smithi , are primarily found along the central Pacific coast of Mexico.

• Biogeographic Regions
• nearctic nearctic
  • native native
• neotropical neotropical
  • native native

Habitat

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 tropical
• terrestrial terrestrial

• Terrestrial Biomes
• rainforest rainforest
• scrub forest scrub forest

Physical Description

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.

• Other Physical Features
• ectothermic ectothermic
• heterothermic heterothermic
• bilateral symmetry bilateral symmetry
• venomous venomous

• Sexual Dimorphism
• female larger

Development

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.

Reproduction

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) 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.

• Key Reproductive Features
• seasonal breeding seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• fertilization fertilization
  • internal internal
• oviparous 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 precocial
• female parental care female parental care
• pre-hatching/birth
  • protecting
    • female
• pre-independence
  • protecting
    • female

Lifespan/Longevity

Female Mexican red-knee tarantulas typically live 25 to 30 years while males rarely live more than 10 years.

Behavior

Mexican red-knee tarantulas are generally docile. When threatened, they rear up to display their fangs. They can also flip barbed hairs off of their abdomen as a defense. Mexican red-knee tarantulas are often aggressive toward rogue spiders, which may be in response to competition.

• Key Behaviors
• fossorial fossorial
• diurnal diurnal
• motile motile
• sedentary sedentary
• solitary solitary
• territorial territorial

Home Range

Little information is available regarding the home range of Mexican red-knee tarantulas.

Communication and Perception

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 visual
• tactile tactile

• Other Communication Modes
• vibrations vibrations

• Perception Channels
• visual visual
• vibrations vibrations
• chemical chemical

Food Habits

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.

• Primary Diet
• carnivore carnivore
  • eats terrestrial vertebrates
  • eats body fluids
  • insectivore insectivore

• Animal Foods
• mammals
• amphibians
• body fluids
• insects

Predation

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.

Ecosystem Roles

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 keystone species

Economic Importance for Humans: Positive

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 pet trade

Economic Importance for Humans: Negative

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 venomous

Conservation Status

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.

Additional Links

Encyclopedia of Life

Contributors

Amanda Giesler (author), Rutgers University, David Zaitz (author), Rutgers University, David V. Howe (editor), Rutgers University, Gail McCormick (editor), Animal Diversity Web Staff.

References

Cites, 2009. "Cites Species Database" (On-line). Cites Species Database. Accessed November 10, 2009 at http://www.cites.org/eng/resources/species.html .

Hansel, M. 1993. Secondhand silk. Natural History , 10: 40-46.

IUCN, 2009. "Euathlus smithi (Red Kneed Tarantula)" (On-line). The IUCN Red List of Endangered Species. Accessed November 10, 2009 at http://redlist.org/apps/redlist/details/8152/0 .

Locht, A., M. Yanez, I. Vasquez. 1999. Distribution and natural history of Mexican species of Brachypelma and Brachypelmides (Theraphosidae, Theraphosinae) with morphological evidence to support their synonymy. The Journal of Arachnology , 27(1): 196-200.

Moya-Larano, J., J. Pascual, . Wise. 2003. Mating patterns in late-maturing female Mediterranean tarantulas may reflect the costs and benefits of sexual cannibalism. Animal Behaviour , 66(3): 469-476. Accessed November 11, 2009 at http://www.uic.edu/depts/ovcr/iesp/Publications/Faculty%20Publications/Wise/Moya-Larano%20J%20et%20al%202003%20Anim%20Behav_Mating%20Patterns.pdf .

Nyffeler, M., W. Sterling, D. Dean. 1994. How spiders make a living. Entomological Society of America , 23(6): 1357-1367.

Orkin, Inc., 2009. "The Mexican Red Knee Tarantula’s Predators" (On-line). Orkin, Inc.. Accessed November 10, 2009 at http://www.orkin.com/other/spiders/the-mexican-redknee-tarantulas-predators .

Peterson, A., D. Osborne, D. Taylor. 1989. Tree trunk arthropod faunas as food resources for birds. Ohio Journal of Science , 89(1): 23-25.

Riechert, S., T. Lockley. 1984. Spiders as biological control agents. Annual Review of Entomology , 29: 299-320.

Skerl, K. 1997. "Spider Conservation in the United States" (On-line). University of Michigan. Accessed November 11, 2009 at http://www.umich.edu/~esupdate/library/97.03-04/skerl.html .

West, R. 2009. "Mexican Red Kneed Tarantula" (On-line). Arkive. Accessed November 10, 2009 at http://www.arkive.org/mexican-redknee-tarantula/brachypelma-smithi/info.html .

Jacksonville Zoo & Gardens. 2008. "Bio Facts: Red Kneed Tarantula" (On-line). Jacksonville Zoo. Accessed November 10, 2009 at http://www.jaxzoo.org/animals/biofacts/RedkneedTarantula.asp .

Nashville Zoo at Grassmere. 2009. "Mexican Red Knee Tarantula" (On-line). Nashville Zoo at Grassmere. Accessed November 10, 2009 at http://www.nashvillezoo.org/animals_detail.asp?animalID=45 .

Oakland Zoo. 2008. "Mexican Red Knee Tarantula" (On-line). Oakland Zoo. Accessed November 10, 2009 at http://www.oaklandzoo.org/animals/arthropods/mexican-red-knee-tarantula .

Sea Studios Foundation. 2002. "Phylum Arhropoda" (On-line). The Shape of Life. Accessed November 11, 2009 at http://www.pbs.org/kcet/shapeoflife/animals/arthropods.html .