Mexican Red Knee Tarantula (Brachypelma smithi) Care Sheet

Brachypelma smithi, better known as the Mexican Red Knee tarantula, is one of the best-known of all theraphosid spiders.

Tremendously popular in the early days of the tarantula keeping hobby, it remains a staple in the trade today. Unlike the early years, where specimens were captured in the wild and shipped worldwide, a CITES listing means all current pet specimens are now captive bred.

The Mexican Red Knee is in many ways the “perfect” tarantula. It grows to a healthy 5-6″ legspan, has a chunky look that is almost “cute” (to some people at least) and is brightly coloured.

This tarantula is primarily black in colour, but benefits from bright orange and yellow hairs on the “knees”, as well as on the abdomen.

Placid in nature, and very long-lived, this is an ideal tarantula for keepers of all abilities and experience levels. The only downside, if there is one, is that Brachypelma smithi tends to be quite a slow-growing species, meaning that you’ll need to be quite patient if you opt to buy spiderlings and rear them to adulthood.

brachypelma smithi photo

Wild Habitat

The Mexican Red Knee was originally described in 1897 by well-known bilogist F.O. Pickard-Cambridge. It is found across a wide range, encompassing the south of North America and areas of Central America.

It’s primary footholds are considered to be in Mexico and Panama, where it may share its range with other members of the genus, most notably Brachypelma emilia, the Mexican Red Leg tarantula.

Tarantula expert Rick West has studied the species in the wild, claiming their burrows are normally to be found “in dense thickets or vegetation” of both dry thorn forests and tropical deciduous forests. Other studies have found burrows frequently near the bases of rocks.

Occupying such a wide variety of environmental conditions, this is an adaptive and sturdy tarantula, which makes it easy to keep in captivity.

As pets, it is generally considered best to adopt a “mid-range” environment, offering an average daily temperature and humidities below those of more decidedly tropical species.

brachypelma smithi photo


One factor which makes Brachypelma smithi such a popular pet is how they seem more willing to sit out in the open than many other tarantula species.

They can therefore be excellent pets for the keeper who wants an impressive display. In truth, many tarantulas hide away for most of the day, rarely to be seen.

Some specimens may not be seen for weeks on end. Not so for the Mexican Red Knee, however, which can often be seen resting in plain sight in their vivarium.

There are a number of considerations when it comes to choosing a cage for your Mexican Red Knee. Tarantulas as a whole can be astonishing escape artists, so the first consideration should be a close-fitting lid and doors that cannot be opened.

The cage should ideally be made of glass or clear plastic, to make observation easier, and should be simple to heat. Tarantulas require a higher relative humidity than occurs in many of our homes, so it is often necessary to mist them gently to raise moisture levels.

A stale and stagnant environment, however, is to be avoided for health reasons. This further impacts the cage selected, as it must offer suitable ventilation to allow air movement and prevent fungal; growth in the warm, moist environment of a tarantula cage.

In terms of dimensions, I have found that Brachypelma smithi tends not to be the most active tarantula, so only a modest-sized cage is necessary. It is also important to point out that these are ground-dwelling tarantulas who naturally build burrows in the wild.

This is in contrast to arboreal species like Avicularia versicolor which build nests off the ground. Cage height for this species is therefore of less concern than for some others.

A cage measuring some 12″ long by 10″ deep should be considered a minimum for adult specimens, though feel free to house them in larger cages if you desire. A cage height of around 12″ is aduequate. In short, a cage roughly 30cm in all directions is a good rule of thumb for this species (and indeed many other Brachypelma tarantulas).

So long as your cage meets all of the above requirements – dimensions, security, ventilation, heating – then it may be used. If you are a new tarantula keeper, considering buying your very first Mexican Red Knee then I recommend you consider looking at Exo Terra cages.

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These are built from glass and offer excellent visibility of your spider. Their hinged doors open up at the front, making it easy to feed and clean your spider, and the lid if made of sturdy mesh to allow air movement.

While they may not necessary be the cheapest tarantula tanks on the market, they are my favourite, as they manage to combine practicality with great looks.

Tank Decor

brachypelma smithi photoBrachypelma smithi is a reasonably undemanding species to keep as a pet, and very few accessories will be required to keep them happy.

It all starts with the substrate, which not only helps to moderate the humidity, but can also be used for burrowing. This is where some disagreement exists among hobbyists. Some claim that it is best to add a thick depth of substrate, so that your tarantula can try to build a burrow. Some 6-8″ of substrate is recommended.

Others point out that wild tarantula burrows can be almost a metre long, so it’s unlikely that your tarantula can build a “wild type” burrow in captivity. Furthermore, it seems even when offered the opportunity to build one, many Brachypelma smithi simply refuse to play ball.

For this reason it is more common these days for hobbyists to offer a far shallower depth of substrate – typically in inch or so of chemical-free potting compost or coconut fibre.

This is supplemented with one or more hides for privacy. A range of different hides are available for tarantulas, though two of the most popular options are either curved pieces of cork bark, or a flower pot laid on it’s side and partially buried.

The hide should be large enough for your Mexican Red Knee to completely conceal itself within for privacy. If you have space to provide more than one hide then all the better; this gives your pet the opportunity to choose the “home” that suits them best.

Tarantulas from around an inch or so in body length should be provided with a very shallow water bowl, which should be cleaned and refilled regularly. While Brachypelma smithi is used to surviving in dry environments, so may not be observed to drink often, it is considered best practise these days.

As a nocturnal species no artificial lighting is required for tarantulas, though if you have the inclination a very low wattage bulb (or one that gives red light) might be used to observe your tarantula after dark.

Lastly, a heater will be required to keep your pet warm enough, but this is covered in more depth below.

Heating & Temperature

Unless you’re lucky enough to live in a very warm part of the world it is likely that your Brachypelma smithi will require some form of artificial heating for most of the year. Only on the hottest summer days will the heater be unnecessary.

The goal is to heat one section of the cage to a comfortable 25-28’C, while leaving another area much cooler. If your spider wants to warm up it can then go and rest in the hot spot, while it can cool down by moving away from it. In this way your tarantula can regulate it’s own body temperature to stay within a comfortable margin.

A range of different tarantula heaters are available on the market, and each should be used with a dedicated thermostat. The thermostat is a separate unit with a sensor on the end of a wire. The sensor is placed into your tarantula cage, and helps to control the amount of heat given out by the heater.

In this way, you can be sure that the heater is running at full speed on cold winter days, but that your spider doesn’t overheat as summer makes an appearance.

For exotic pet keepers with just a handful of tarantulas, possibly the best solution is a heat mat. These are thin heaters made of plastic, with a wire coming out of one side. They can easily slip under a tarantula tank, or be attached to the side to provide a gentle background warmth.

These heat pads are available in a wide range of different dimensions to suit most situations. For a single specimen, just a small mat of around 30cm square is suitable. For keepers with a range of spiders one of the so-called “heat strips” which are long and thin can be used to heat a number of spider tanks.

Reptile thermometers can be bought for next to nothing and should be used to confirm that (a) the hotter area is reaching a suitable temperature and that (b) the opposite end of the cage is noticeably cooler.

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The easiest option is simply to stick the heat mat to one side of the cage, safe in the knowledge that the other side will be cooler.

Water & Humidity

brachypelma smithi photo

As described earlier, an open water dish should be available at all times, but it is important that this is shallow. Tarantulas are not known for their swimming abilities, so the shallow dish reduces the risk of drowning.

A humidity of around 70% is ideal for Brachypelma smithi, which may be similar to that of most homes. A hygrometer can be used to help monitor humidity levels to ensure they are acceptable.

It can be a good idea to gently mist your Mexican Red Knee cage once or twice a week, to offer a gentle “boost” in humidity. Some tarantulas also seem to prefer drinking these find droplets off the wall of the cage, rather than making use of their water bowl. Pay particular attention when a moult is nearing, where it can be wise to bump up the moisture levels to prevent any problems.

A houseplant mister works well for this purpose, though be sure it hasn’t contained any unpleasant chemicals before. It is generally best to buy a brand new mister and label it as “tarantulas only” to be certain.

Note that as Brachypelma smithi survives quite admirably in drier environments in the wild, it is critical to avoid a cage that is soaking wet. The substrate should be allowed to dry out slightly between mistings, which if you’ve got the temperature and ventilation right should occur quite rapidly.


Brachypelam smithi is quite a slow growing and long-lived species. Females may live for 20 years or more, but both sexes take quite some time to reach maturity. Unlike many more tropical species, the Mexican Red Knee has a far more sedate appetite. Twice-weekly feedings for youngsters and once or twice a week for adults tends to work well.

Note that the Mexican Red Kneed tarantula may go off it’s food for long periods of time, as they might during cooler weather in the wild. Some of my specimens stop eating for a month or more, especially before a moult. This is generally not anything to be worried about, assuming your spider appears otherwise to be in good spirits.

As mid-sized spiders Mexican Red Knees can eat any of the popular feeder insects. I primarily feed mine on locusts, though crickets and roaches are also options. Some may even take the odd pinky mouse if they’re feeling particularly hungry.

It is difficult to overfeed a tarantula, so feel free to feed as often as they will eat. It can be a smart idea to keep a feeding chart, so that you get used to how much and how often your spider eats. Such records also make it easier to ascertain when the next moult is likely to be happening.

I generally feed my tarantulas in the evening, as they are naturally starting to wake up. Any uneaten food is then removed the following morning to prevent it annoying the spider.


One of the reasons that the Mexican Red Knee is so popular – and has been used in so many TV shows and movies – is simply how docile it is. Indeed, of all the tarantulas common in the trade, this is arguably one of the very best for handling.

They are slow moving, very rarely try to bite and attain a healthy size for the average adult to hold.

The one thing you must be careful of when handling this species are the so-called “urticating hairs”. These hairs can be kicked off if your tarantula feels stressed, and can cause irritation. One study records the hairs of Brachypelma smithi leading to “itchy, gritty eyes”. The best bet, therefore, is to keep your spider well away from your face if you choose to handle it.

In brief, while experts recommend handling theraphosids as little as possible – for the safety of the spider – if you do want a spider that you can hold on occasion then you can’t do much better than the Mexican Red Kneed tarantula.

Images c/o brian.gratwicke, davidricardoabrenica & James St. John


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