Brachypelma auratum Care Guide

The Mexican Flame Knee

Revision Date: March 2025

Introduction

Today we’re diving into the care of the Mexican Flame Knee tarantula, Brachypelma auratum. This striking New World terrestrial species hails from the savanna and scrubland regions of Guerrero and Michoacán in Mexico. With its vivid red knees, bold white bands on black legs, and gentle demeanor, it’s a favorite among tarantula enthusiasts. Not only is it visually stunning, but its docile nature and ease of care make it an excellent choice for beginners.

Quick Species Snapshot

• Scientific Name: Brachypelma auratum

• Common Names: Mexican Flame Knee Tarantula

• Type: Terrestrial

• Native Range: Guerrero and Michoacán regions of Mexico

• Size: Approximately 5.5” diagonal leg span (about 14 cm)

• Growth Rate: Medium – Slow

• Life Expectancy: Females 25-30 years; Males around 10 years

• Experience Level: Beginner

What Makes B. auratum So Special?

The Mexican Flame Knee stands out with its eye-catching color contrast, bright red knees and bold white bands on black legs create a truly dynamic look. In the wild, these tarantulas have even been observed cohabitating with Eleutherodactylus occidentalis, a frog species that may help control pests around the tarantula’s hide or egg sac. While its venom is not medically significant, it does possess urticating hairs that can cause mild irritation, so caution is advised during handling.

Taxonomy, Etymology & Research Update

Brachypelma auratum, commonly known as the Mexican Flame Knee tarantula, is a striking species native to the Pacific coastal regions of Guerrero and Michoacán in Mexico. This species is renowned for its bold black coloration accented by vibrant red-orange markings on the patellae (knees), resembling flames, hence the common name "Flame Knee." Due to its visual similarities to Brachypelma hamorii (formerly Brachypelma smithi), B. auratum was not formally described as a distinct species until 1992.

The genus name Brachypelma comes from the Greek words "brachys", meaning "short," and "pelma", meaning "sole" or "foot," likely referring to the compact build and dense scopulae on the spider’s feet that aid in climbing. The species name auratum is derived from the Latin word "auratus," meaning "golden," possibly referencing the golden hue found on the carapace or the flame-like knee patterns that distinguish this species.

Recent taxonomic studies have led to significant revisions within the Brachypelma genus. A major review in 2017 determined that Brachypelma was not monophyletic, leading to the creation of the Tliltocatl genus for certain species. However, Brachypelma auratum remained within Brachypelma, reinforcing its place among the more recognizable Mexican red-legged species.

A Species at Risk

The Mexican Flame Knee is currently listed as Near Threatened by the IUCN (as of 2018). Threats include habitat destruction, human persecution, and trapping for the pet trade. Captive breeding has helped lessen the demand for wild-caught specimens, so sourcing captive-bred individuals from reputable breeders is encouraged.

Housing & Substrate – Terrestrial Setup

Spiderlings

• Enclosure Size:
  Use a small acrylic enclosure (e.g., Sling Crib, 3" Tarantula Cube, Small Slider Crib, Small Cuboid, Terrestrial Sling Crib, Slider Crib Mini, or Cuboid Mini) that is no smaller than three times the tarantula’s leg span. We recommend enclosures by Tarantula Cribs for their proven quality and safety.

• Substrate:
  Fill at least 2/3rds of the enclosure with Terra Aranea by The Bio Dude.

• Humidity:
  Maintain a slightly damp substrate (but not swampy) by offering a small water dish or gently dripping water on one corner about once a week.

Juveniles

• Enclosure Size:
  Use a medium enclosure (e.g., Medium Slider Crib, 6" or 8" Tarantula Cube, or Medium Cuboid) that is at least 3–4× the tarantula’s leg span.

• Substrate:
  Fill the enclosure 1/2 to 2/3 full with Terra Aranea by The Bio Dude. This depth ensures ample space for burrowing while minimizing the risk of injury from falls.

• Humidity:
  Keep the substrate mostly dry with a full water dish; occasionally overflow one corner to create a slightly damp area.

• Additional Features:
  Provide a half cork bark round for a secure hide.

Adults

• Enclosure Size:
  Use a large enclosure (e.g., Large Slider Crib, 12" Cube Switch, 12" Cube, 18" Cube, or Terrestrial XL) that is at least 3× the tarantula’s leg span (ideally 4× for enhanced natural behavior, while considering escape risks). Enclosures by Tarantula Cribs are highly recommended.

• Substrate:
  Fill the enclosure 1/2 to 2/3 full with Terra Aranea by The Bio Dude to provide sufficient depth for burrowing while reducing the risk of falls.

• Additional Features:
  Include a secure hide (preferably a half cork bark round) and a shallow water dish. Ensure the enclosure is a horizontal rectangle (wider than it is deep) with secure ventilation and a tight, secure lid to prevent escapes.

Note:
The general rule of thumb for tarantula enclosures is that the enclosure should be no smaller than three times the tarantula’s leg span for spiderlings, 3–4× for juveniles, and 3–4× for adults. This ensures ample space for natural burrowing while minimizing fall risk. Remember, tarantulas are escape artists, so always verify that ventilation holes, lids, and gaps are too small for your tarantula to squeeze through. They can and will climb glass and other smooth surfaces.

Affiliate: Please use Tarantula Cribs (affiliate code TTC10) and Terra Aranea by The Bio Dude for substrate.

Temperature & Humidity

• Temperature: Aim to maintain a room temperature between 68°F and 76°F (20-24°C); slight variations are acceptable.

• Humidity: Moderate humidity is best. Spiderlings benefit from a slightly damp substrate, while adults thrive with generally dry substrate and only occasional dampening.

Feeding Schedule

Spiderlings

• Frequency:
  Feed twice a week.

• Prey:
  Offer small prey such as flightless fruit flies, confused flour beetles, or pre-killed tiny crickets/roach nymphs. Remove any uneaten prey after 24 hours. increase the size of the prey as the spider grows. Prekill any prey that is over 2/3 the size of the sling. For more detailed information on feeding spiderlings, watch this video: How To Feed Spiderlings & Scorplings (Baby Tarantulas & Scorpions)

• Post-Molt:
  Wait 24–48 hours after a molt before feeding. Ensure that the tarantula’s fangs are solid black and its exoskeleton is not soft or shiny.

Juveniles

• Frequency:
  Feed every 7–10 days.

• Prey:
  Provide 2–3 small to medium crickets or a medium Dubia roach.

• Feeding Guidelines:

  • If the abdomen is thinner than the widest part of the carapace, feed more prey more often.

  • If the abdomen is wider than the carapace, feed less prey, less often.
    This strategy helps prevent obesity, which can lead to molting complications or increase the risk of an abdomen rupture from even a small fall.

• Post-Molt:
  Wait 3–7 days after a molt before feeding, ensuring that the tarantula’s fangs are solid black and its exoskeleton is fully hardened.

Adults

• Frequency:
  Feed every 2–3 weeks (or as needed).

• Prey:
  Offer 4–5 large crickets or one large Dubia roach.

• Feeding Guidelines:

  • If the abdomen is thinner than the carapace’s widest part, increase feeding frequency.

  • If the abdomen is wider than the carapace, reduce feeding frequency.
    This is crucial to avoid obesity, which can interfere with proper molting or cause dangerous issues such as an abdomen rupture.

• Post-Molt:
  Wait 5–10 days after a molt before feeding, ensuring that the tarantula’s fangs are solid black and its exoskeleton is fully hardened.

Behavior & Temperament

The Mexican Flame Knee is known for its docile, easygoing temperament. While generally calm and curious, these tarantulas are primarily display animals that may remain motionless for long periods, only moving when stimulated by potential prey or environmental changes. They are not known to be aggressive; however, they do possess urticating hairs that can cause irritation if they contact your skin, eyes, or mucous membranes. As with all tarantulas, it’s best to avoid excessive handling and to check their behavior, especially after molting, before interacting with them.

Breeding Brachypelma auratum in Captivity

Breeding Brachypelma auratum (Mexican Flame Knee) is a slow but rewarding process due to their long maturation period and selective breeding behaviors. Since this species is protected under CITES regulations, captive breeding is essential to ensure that wild populations remain undisturbed while keeping this stunning tarantula available in the hobby.

Sexual Maturity & Pairing

• Male Maturity: Males typically mature within 4–7 years, developing tibial hooks and enlarged pedipalps for sperm transfer.

• Female Maturity: Females take significantly longer, often 8–12 years, before reaching full reproductive maturity.

• Pre-Pairing Preparation: We should ensure the female is well-fed before pairing to minimize defensive responses. Some breeders also recommend increasing humidity slightly to mimic seasonal breeding cues.

Mating Process

• Introduce the male at night, when both tarantulas are naturally more active.

• The male will drum on the substrate to signal his presence.

• If receptive, the female may drum back or remain still, allowing the male to lift her with his tibial hooks and insert his emboli.

• Once mating is complete, the male should be removed immediately, as females can become defensive post-mating.

Egg Sac Production

• If fertilization is successful, the female will begin developing an egg sac 4–6 months after mating.

• Maintain temperatures around 72–78°F (22–25°C) with humidity levels of 60–70% to support egg sac development.

• The egg sac typically contains 400–800 eggs, though numbers can vary.

Egg Sac Handling (Optional)

• Some breeders prefer to pull the egg sac after 30–45 days for artificial incubation.

• If left with the mother, 1st instar spiderlings will emerge in 8–10 weeks, molting into 2nd instar within 3–4 weeks.

Raising Spiderlings

• Once the spiderlings reach 2nd instar, we should separate them into individual enclosures.

• Feed them pinhead crickets, flightless fruit flies, or small roaches every 3–4 days.

• Keep humidity levels moderate and allow part of the enclosure to dry out between mistings to prevent mold growth.

Challenges & Considerations

• Female selectiveness: Some females may reject males outright, requiring multiple introductions to achieve successful pairing.

• Long maturation time: With slow growth rates, breeding B. auratum requires years of patience.

• Male lifespan: Males typically do not live beyond a year after maturing, so breeding attempts should be made as soon as possible.

As a CITES-protected species, Brachypelma auratum should never be taken from the wild. By supporting captive breeding efforts, we help reduce pressure on wild populations while ensuring a steady supply of healthy, well-acclimated specimens. Captive breeding also helps maintain genetic diversity and contributes to the long-term sustainability of this species in the hobby.

Final Thoughts

Brachypelma auratum, the Mexican Flame Knee, is easily one of my favorite Brachypelma species… most of the time. And trust me, that’s saying something, considering how many stunning, red-kneed tarantulas exist in this genus. But there’s just something about that bold black body, fiery red knees, and crisp white striping that makes this species stand out. It’s like the tuxedo of tarantulas: classy, elegant, and always looking its best.

This is a fantastic tarantula for beginners and experienced keepers alike. It’s hardy, low-maintenance, and generally docile, meaning you won’t be dealing with a teleporting spider every time you open the enclosure. Plus, if you’re looking for a pet tarantula you can show off without worrying about it going full-on defensive, B. auratum is an excellent choice. Just make sure you have patience because, like most Brachypelma, this species takes its sweet time growing. But hey, the longer the wait, the longer you get to enjoy them once they’re full-sized, right?

If you want to see this species in action, check out my Nature Documentary and Care Guide Video on the Mexican Flame Knee. I cover everything you need to know to properly care for them, plus you get to see some stunning footage of this tarantula being its magnificent self.

Also, let’s be honest, Mexican Red-Legged Tarantulas are confusing as hell. If you’ve ever found yourself second-guessing whether you’re looking at a Mexican Red Knee, a Smith’s Red Knee, a Mexican Red Leg, a Fire Leg, or a Flame Knee, you’re not alone. That’s exactly why I made the EXPLAINED! Mexican Red Tarantula CONFUSION - Flame, Fire, & Blood video. It breaks down all the major red-legged Brachypelma and Aphonopelma species with side-by-side comparisons, geographic ranges, and clear explanations so you never mix them up again. Seriously, if you’re into Brachypelma, you need to watch it.

So, if you’re looking for a beautiful, beginner-friendly, long-lived tarantula that won’t send you running every time you lift the lid, the Mexican Flame Knee is the one for you. Just be prepared to have people constantly ask, “Wait, is that a Red Knee?” and enjoy the satisfaction of explaining why it’s actually so much cooler.

Additional Recommendations:
For enclosures, you might consider Tarantula Cribs with the affiliate code TTC10 for a 10% discount, and I suggest using Terra Aranea by The Bio Dude for substrate. For purchasing tarantulas online, a great option is Spider Shoppe — just use code TTC10 for 10% off. Also, check out the Dealer & Discounts section on my website for additional recommended dealers and discount codes.