AT A GLANCE
- Common Name: Mexican Redknee Tarantula
- Scientific Name: Brachypelma hamorii
- Category: Invertebrates
- Subcategory: Arachnids
- Size: Diagonal leg span: 5.5–6.5 in (14–16.5 cm); Carapace length: 2.0–2.5 in (5.0–6.5 cm)
- Weight: 0.5–1.8 oz (15–50 g); Gravid mature females can reach 2.0 oz (60 g)
- Lifespan: Females: 25–30+ years; Males: 5–7 years (dying shortly after reaching sexual maturity)
- Diet: Carnivore / Nocturnal sit-and-wait predator (crickets, grasshoppers, roaches, beetles, small lizards, and tiny mice)
- Habitat: Deep underground burrows beneath large rocks, tree roots, and dry scrub hillsides
- Range: Pacific coastal dry forests and scrub of southwestern Mexico
- Conservation Status: Vulnerable (IUCN Red List / CITES Appendix II)
Overview
The Mexican Redknee Tarantula (Brachypelma hamorii, formerly classified alongside Brachypelma smithi) is a world-famous, docile, and strikingly beautiful terrestrial tarantula belonging to the family Theraphosidae, native to the Pacific coastal scrublands and dry forests of southwestern Mexico. Celebrated as the quintessential Hollywood movie spider and one of the most widely recognized arachnids on Earth, it is instantly identified by its velvety jet-black body accented by brilliant, flame-orange to scarlet-red bands on its patellae (‘knees’) and leg joints, contrasted with a creamy-gold bordered carapace.
In Mexican tropical deciduous and arid thornscrub ecosystems, Mexican redknee tarantulas occupy an important ecological niche as long-lived, solitary ground-dwelling predators. Utilizing silk-lined subterranean burrows excavated beneath rocks and fallen logs, they venture out at night to capture insects, scorpions, and small vertebrates, keeping insect populations in check. Furthermore, their presence supports specialized desert food webs, serving as the obligate hosts for parasitoid tarantula hawk wasps (Pepsis species) that paralyze tarantulas to feed their larvae.
Biology and Physical Characteristics
Brachypelma hamorii possesses remarkable biomechanical and defensive specializations. On the dorsal surface of its abdomen, it carries thousands of microscopic, barbed urticating hairs (Type I and Type III setae) that it kicks off with its hind legs when threatened, creating a floating cloud of irritating bristles that lodge in the eyes and mucous membranes of mammalian predators. Its massive, downward-striking chelicerae (fangs) measure up to 0.4 inches (1 cm) in length, injecting a mild, digestive venom that liquefies prey tissues internally, allowing the spider to drink the liquefied nutrients through its muscular sucking stomach.
Behavior and Ecology
Mexican redknee tarantulas are strictly nocturnal, terrestrial sit-and-wait ambush predators that spend daylight hours sealed inside their deep, humid burrows behind a curtain of silk webbing that blocks midday desert heat. At night, they position themselves at the burrow entrance with their legs resting on silk tripwires that detect the delicate ground vibrations of passing insects. Females exhibit extraordinary longevity, molting annually and continuing to reproduce for decades, while mature males develop tibial mating hooks on their front legs to hold the female’s fangs during courtship.
Conservation and Human Impact
Assessed as Vulnerable by the IUCN Red List and protected globally under CITES Appendix II, Brachypelma hamorii suffered devastating historical wild declines in the 1970s and 1980s from massive over-collection for the international pet trade. While widespread captive breeding has virtually eliminated pet trade pressure on wild populations, the species currently faces severe habitat destruction from coastal resort development, highway construction, and agricultural conversion.
Interesting Factoid
A female Mexican redknee tarantula can live for more than 30 years—longer than most pet dogs and cats—and can kick clouds of microscopic barbed hairs from its belly that blind and repel predators.