Brachypelma auratum Schmidt, 1992 is the Mexican Flame Knee tarantula from Mexico. Its orange, flame-shaped markings sit on the patellae, the knee segments of the legs, but identification also uses the genitalia.13 We found it in the wild in Guerrero, Mexico, in the first film below.
Mexican Flame Knee and flame knee tarantula refer to B. auratum. The Mexican red-knee tarantulas, B. smithi and B. hamorii, are separate species.
Quick facts
- Scientific name: Brachypelma auratum Schmidt, 1992.1
- Common name: Mexican Flame Knee tarantula.
- Identification: Orange, flame-shaped patellar markings are a useful visual cue, not a diagnosis by colour alone.23
- Range: Mexico, with published conservation work placing its known and modelled range mainly in the Balsas River Basin.4
- Size: A published redescription measured an adult female at 61 mm body length and an adult male at 42 mm, both without chelicerae and spinnerets.3
- Natural history: A fossorial species associated with burrows.4
- Trade: Regulated under CITES. Trade regulation and conservation-risk assessment are different questions.1
How to identify Brachypelma auratum
Mendoza and Francke published a systematic revision of red-kneed Brachypelma in 2017, which redescribed B. smithi and B. hamorii and used DNA barcodes that included B. auratum.2 In their broader 2020 revision, they redescribed male and female B. auratum and retained it in Brachypelma.3 That treatment uses diagnostic morphology and molecular evidence, so a colour pattern should only guide observation.
In the first film below, shot in Mexico, the spiders appear predominantly dark with orange markings at the knees. That is a description of the recorded animals, not a substitute for the published diagnosis. The second film, further down, follows a separate Mexico search day that turns up other tarantulas and does not show B. auratum.
The provisional Aphonopelma mooreae identification shows the opposite problem: its photograph does not reveal the characters needed to confirm the species.
What does Brachypelma auratum look like?
Both sexes are mostly black, and Mendoza and Francke describe the same leg pattern for males and females: black femora, mostly black tibiae and metatarsi with sparse brownish-pink hairs, black feet, and on each patella an orange flame-shaped mark followed by a pale ring.3 That mark gives the species its common name, and their diagnosis names it as the feature that separates B. auratum from every other known Brachypelma, alongside differences in the genitalia of both sexes.3
The body colour differs a little between the sexes in the live animals they examined: males have a peach-coloured edge to the carapace, while females have a light brown edge that in some individuals extends behind the fovea, the central pit of the carapace. In both sexes the abdomen is black with sparse rose-coloured hairs, and a single patch of urticating hairs of types I and III sits at the back of the abdomen.3
How big does Brachypelma auratum get?
Two sets of figures exist, and they measure different things. The 2020 redescription measured single adults, a female with a body length of 61.4 mm and a carapace 26.3 mm long, and a male with a body length of 42.1 mm and a carapace 18.2 mm long, both without chelicerae and spinnerets.3 Leg IV is the longest in both sexes, at 70.6 mm for the female and 69.9 mm for the male when the segments from femur to tarsus are added together.3
The 2019 conservation profile lists 70 mm for females and 60 mm for males and does not say which measurement it uses.4 The measured figures are body and carapace lengths and a sum of leg segments rather than a leg span, and the two measured animals are single specimens, not a recorded maximum.
Range and habitat
Brachypelma auratum is endemic to Mexico. A conservation assessment places its known and modelled range mainly in the Balsas River Basin, north of the Sierra Madre del Sur and south of the Trans-Mexican Volcanic Belt. Records extend through parts of Jalisco, Michoacán, Guerrero and the State of Mexico.4
The conservation profile describes B. auratum as a fossorial species associated with burrows. It does not establish one universal burrow design or prove an adaptive reason for the presence or absence of silk at the entrance.4
The Balsas basin lies on the inland side of the Sierra Madre del Sur, and the conservation profile describes its thorn and dry deciduous forest as seasonally much hotter and drier than the Pacific coast for several months of the year.4 The profile says B. auratum does not occur in the coastal lowlands, where the mountains act as a barrier, gives an elevation range of 130 to 2,030 m, and reports a preference for low and medium altitudes and a warmer climate.4 It overlaps with Brachypelma albiceps only at the eastern edge of its range in Guerrero.4
Mendoza and Francke describe the burrows as modified or self-excavated cavities under large rocks and large tree roots among thorny brush, with no silk around the entrance.3 According to the profile, juveniles are often found in scrapes under stones, and the broad, rather horizontal burrows can look like those of ground squirrels, which have been seen alongside B. auratum at some sites.4
The profile describes the spiders as nocturnal ambush predators that wait near the burrow entrance from dusk into the night and feed mainly on ground-dwelling arthropods.4 It places the mating season at the end of the rainy season and the start of the dry season, from August to January, when mature males wander in the open, and it says adult females typically moult once a year and lay their egg sacs in the drier winter months.4
For other Mexican field material on this site, see the Tliltocatl epicureanus field account, or the Mexican Red Knee Tarantula: Smithi vs Hamorii comparison. For a Costa Rican tarantula of the genus Tliltocatl, formerly placed in Brachypelma, see the curly hair tarantula.
Conservation and trade
The species is regulated under CITES, and the World Spider Catalog links its record to that trade restriction.1 The 2019 conservation profile assessed habitat loss and collection pressure across its Mexican range and treated the available evidence cautiously because population data remain limited.4
Captive breeding may reduce demand for wild animals, but a captive animal is not evidence that a wild population is secure. Ask for a clear captive-bred history and locality information where it exists. Do not collect this species from the wild.
My captive observation
In my Christmas tank tour, I show an adult female B. auratum using a hide under a log in her planted enclosure. You can watch the tank tour, or see more of my setups in the enclosure films. That is one animal in my collection, rather than a tested care setup for the species.
Frequently asked questions
Is Brachypelma auratum the Mexican Flame Knee tarantula?
Yes. Mexican Flame Knee is a common name used for Brachypelma auratum. The scientific name is the more precise reference.1
How can I identify Brachypelma auratum?
Orange to red-orange flame-shaped markings on the patellae are a useful visual cue. They are not definitive on their own. Published diagnostic work uses more than visible colour pattern.23
Where does Brachypelma auratum occur?
It is endemic to Mexico. Published conservation work places its known and modelled range mainly in the Balsas River Basin in south-central Mexico.4
Is Brachypelma auratum regulated by CITES?
Yes. The World Spider Catalog links the accepted species record to a CITES trade restriction. CITES regulates international trade. It is not an IUCN conservation category.1
How big does Brachypelma auratum get?
The 2020 redescription measured an adult female at 61 mm body length and an adult male at 42 mm, and the 2019 conservation profile lists 70 mm for females and 60 mm for males without saying what it measures. The redescription gives body and carapace lengths, not a leg span.34
Is the Mexican flame knee the same as the Mexican red knee?
No, because the 2017 revision by Mendoza and Francke treats the Mexican red-knee tarantulas as Brachypelma hamorii and Brachypelma smithi, and Brachypelma auratum is a separate species that the 2020 diagnosis sets apart by its flame-shaped orange patellae.23 The two red-knee species are compared on the Mexican Red Knee Tarantula: Smithi vs Hamorii page.
More field footage
Notes from the field, by email
I send a short tarantula briefing by email, with field notes from our trips written for the newsletter when I have them, and once a month a roundup of new posts. It is free, and you can unsubscribe at any time.
Later, if you want to support the fieldwork and the films, I am also on Patreon.
References
- World Spider Catalog. 2026. Brachypelma auratum Schmidt, 1992. Version 27, Natural History Museum Bern. Accessed 28 July 2026.
- Mendoza, J. I. and Francke, O. F. 2017. Systematic revision of Brachypelma red-kneed tarantulas, and the use of DNA barcodes to assist in the identification and conservation of CITES-listed species. Invertebrate Systematics 31(2): 157 to 179.
- Mendoza, J. and Francke, O. 2020. Systematic revision of Mexican threatened tarantulas Brachypelma, with a description of a new genus, and implications on conservation. Zoological Journal of the Linnean Society 188(1): 82 to 147.
- Fukushima, C. S. and colleagues. 2019. Species conservation profiles of tarantula spiders listed on CITES. Biodiversity Data Journal 7: e39342.
- Schmidt, G. 1992. Brachypelma auratum sp. n., die sogenannte Hochlandform von Brachypelma smithi. Arachnologischer Anzeiger 3(8): 9 to 14.
The Texas brown tarantula is Aphonopelma hentzi, a North American species, not Brachypelma auratum.
