A widely-recognised species, the Mexican red knee is perhaps one of the most popular known, and kept tarantulas. It’s a beautiful, hardy species that is particularly docile, making it very attractive to hobbyists in the arachnid field. Although a venomous species, its bite is not life threatening.
Found in Mexico as the name suggests, the red knee is often found burrowed away within deciduous tropical forests on hilly terrain or in desert areas near the pacific coast. Burrowing provides refuge from daytime temperatures, and predators such as birds and reptiles.
The Mexican red knee is unmistakable with its colouration. They have a black abdomen which is covered with fine, fiery red/orange urticating hairs, as well as a similarly black carapace outlined by a deep tan colour. The bend (knee) on each of their legs is bright orange with bands of reddish brown and black continuing down the leg. Although they have 8 eyes located around their head, their vision is somewhat poor. To make up for this, their legs are covered in small hairs which sense vibrations, coming from nearby prey or predators. The palps on the end of each leg allow them to smell, taste and feel, followed by two tiny claws on the end of each foo which enables them to climb slippery surfaces.
Determining the sex of this species, and tarantulas in general, is not usually possible through initial observation alone until they reach sexual maturity. Males at such a point will emerge from their moult with small shiny structures known as papal bulbs on the end of their pedipalps along with one embolus per papal bulb (these are used for transferring sperm to the females). Another obvious male characteristic in most species is the tibial spurs at the end of the tibias on the first set of legs. These can vary between species, with most being hook like structures and others being mounds of smaller spines. An educated guess as to whether the individual is male before it reaches sexual maturity is possible, especially within captive bred groups, as males are generally known as being spindlier due to being smaller in size than females. Females are generally larger, more heavily built and aggressive when it comes to temperament. Another common way to sex tarantulas is to assess their moulted skin. This can achieve sexing at an earlier age, however in most cases of younger tarantula, requires the use of a microscope and a trained eye. The interior of the abdominal area is examined for the presence of a spermathecae, which is the area in which the female stores sperm. In larger individuals, the spermathecae can be identified by the naked eye, however can also easily be mistaken for a male’s accessory organs in some species.
Each moult leads to an increase in growth, resulting in an average size of 4 to 6 inches. During this time, internal organs are replaced such as the stomach lining, and lost appendages can also be regrown. A few weeks before the moult occurs, a new skin begins to develop under the existing one. Whilst undergoing this process, the tarantula becomes lethargic, loses its appetite and may begin to increasingly spin a web. When the actual moult begins, it will lie on its back, and appear although it’s dead. Proving the environment holds the right humidity, the tarantula will emerge from its old skin fairly quickly and smoothly. Post moult, the tarantula is very soft and takes a period of rest (usually up to 2 weeks) to recover and harden up before attempting to feed.
Breeding generally occurs during autumn, across the months of July to October. A mature male begins by spinning a sperm web. He will then approach a female, or the shelter in which she is in, tapping and vibrating his legs. This gains the females attention, and if burrowed away, lures her out. The male then pushes the female upright, holding her fangs back using his tibial spurs. This enables him to transfer packets of sperm into her spermathacae where they will remain until she lays her eggs. After the sperm has been transferred, he has a very small window to get away before the female eats him. If the mating is successful, the female will lay up to 1000 eggs, and wrap them in a silk bundle along with the male’s sperm. Around 9 weeks later the eggs begin to hatch. The Mexican red knee is a slow growing species, although if consistently fed, the spiderlings can reach adulthood quicker. On average, females mature at around 7 years of age and can live up to the age of 30. Males mature a lot faster at 4 years of age, however also have a much shorter life span of around 10 years of age.
The Mexican red knee is an ambush species, that patiently waits within a burrow for prey to pass, before lunging out at high speed to inflict its victim with a venomous bite, and dragging it back into their burrow. The venom is injected through their two hollow fangs, which firstly paralyses their prey, then liquidises them for consumption.
Young individuals feed mainly on crickets and other small insects, however adults can also take down small mice, frogs and lizards.
According to the IUCN, the Mexican red knee is a near threatened species, despite successful captive breeding attempts and are now protected in the wild. Their habitat is increasingly being destroyed by climate change and local farming, alongside many being captured to be sold in the illegal pet trade. They also face a natural threat from insectivore predators, such as birds and reptiles. As a means of defence when feeling threatened, the Mexican red knee will flick its urticating hairs off its abdomen. These hairs are barbed and dig into the skin, causing irritation or an uncomfortable rash. In some cases, if these hairs penetrate the organisms eyes they can cause blindness.