Scientific Name Brachypelma Smithi
Conservation Status Near Threatened
The Mexican red knee tarantula is coloured black with brown hairs across most their body. At the leg joints are the red bands from which their name is derived. Their carapace is beige with a black square at the centre. The upper section of the leg is orange.
On the back legs the hairs are known as ‘urticating hairs.’ This means that they can flick them off in to a predator who is threatening them. These irritate the eyes and skin of the predator allowing the spider to escape.
The leg span of the red kneed tarantula is 15-17cm (5.9-6.7in). Their weight ranges from 15-16g (0.5-0.6oz). The genders appear similar but males do have a slightly smaller body and longer legs.
Lifespan differs between the 2 genders. While a female may live for between 20 and 30 years it is more common for a male to live for up to 5 years.
The Mexican red knee tarantula is a carnivore. They prey upon a range of animals such as insects, small reptiles, frogs and birds along with rodents.
Their prey is located using a sensitive patch on the end of each leg which can be used to detect smells, tastes and vibrations.
These animals acquire most of their food by waiting for it to walk across the top of their burrow. Once they catch a prey item it is held between the front legs and they use their two hollow fangs to inject their venom in to the prey item. As this venom enters the prey it liquefies their body and eventually they consume the prey by drinking the juices.
Mexico Is the native home of the Mexican red knee tarantula. Here they live along the central Pacific coast.
The Mexican red knee tarantula can be found amongst the scrublands, deserts, deciduous forests and dry thorn forests. They dig a burrow in a soil bank in which they can live. It allows them to maintain a constant temperature and humidity year-round to help them not dry out from the heat. At the entrance, they have a carpet of web.
Males mate for the first time after their maturing moult. This generally occurs throughout July and August which is the rainy season.
When a male finds a suitable female, he uses the front limbs (known as pedipalps) to deposit her sperm onto the female’s abdomen. She retains this here till the spring when she forms a silk mat. On to this her 200 to 400 eggs are deposited. These then fertilise and she wraps them in the silk to form an egg-sac. This is carried between the fangs for the next 1 to 3 months till they hatch.
For the first 3 weeks of life they spend their time in the egg sac. A further two weeks is spent in the burrow before they disperse to live alone.
As they grow they moult their old skin. Their skin does not stretch and as such must be replaced with a new one each time they grow. During this time they lie upon their back and wait for the skin to shed. They will take a while to begin eating again once they moult as their fangs shed as well. The new skin takes time to harden making it difficult to eat for up to a month.
It takes 20 moults over a period of roughly four years before the red kneed tarantula will moult to become an adult.
Soon after this moult they are sexually mature.
Predators of the Mexican red knee tarantula includes birds, moths and lizards. To defend against predators, they use their urticating hairs to irritate their skin or send them blind if it gets in their eyes.
They also have a venom. This is mildly harmful to humans and causes a reaction like a bee sting. Like all bites an allergy can cause more severe reactions.
Most of their activity takes place during the night.
Mexican red knee tarantulas are commonly kept as exotic pets.
Top – Public Domain
Bottom – By Brian Gratwicke from DC, USA (Brachypelma smithi) [CC BY 2.0 (http://creativecommons.org/licenses/by/2.0)], via Wikimedia Commons