Members of the reduced genus Brachypelma (the "red leg" group) are considered to be in most urgent need of further conservation efforts.

Members of the family Theraphosidae, the tarantulas, to which Brachypelma belongs, are generally large compared to other spiders, and are commonly seen as "objects of dread".

[6] The distribution of hairs on the legs and palp and the shape of the male and female genitalia are the diagnostic features of the genus.

The male palpal bulb has a flattened, spoon-shaped embolus; females have fused spermathecae, with a flat cross-section.

[7] Brachypelma can be distinguished from Tliltocatl by presence of the red or orange patterns on the legs of all species except B. albiceps, which can be recognized by the golden yellow carapace.

The shape of the genitalia differs between the genera; the apex of the male palpal bulb is shorter in Brachypelma and the female spermatheca baseplate is more strongly developed and hardened.

These have a single entrance, a little larger than the spider, opening into a horizontal tunnel that usually leads to two chambers: one where it molts and one where it rests and consumes its prey.

[6] North American tarantulas like Brachypelma are "sit and wait" predators, seizing prey passing by the burrow entrance.

[10] Studies on species in the wild showed that pre-adult and adult spiders molt towards the end of the dry season, which lasts from June to November.

[citation needed] The genus Brachypelma was erected by Eugène Simon in 1891 for the species Mygale emilia, originally described in 1856.

Although B. hamorii and B. smithi are very similar in external appearance and have not always been treated as separate species, they are clearly distinguished by their DNA barcodes.

A cladogram based on Bayesian analysis of a sample within their proposed tribe Theraphosini is shown below,[16] with current genus names added.

The authors cautioned that the necessary use of specimens obtained through the commercial pet trade meant that their exact geographical origins were often unknown, leading to uncertainty as to their identification.

Stuart Longhorn has criticized several arachnologists, including Günter Schmidt, for describing new species based on pet-trade specimens without accurate locations, resulting in vague or inaccurate distributions.

He argues that locality information is vital for "scientific rigor", since without it important questions relating to the identity of species cannot be answered.

[17] Steven Turner and colleagues have also noted difficulties in identification resulting from the use of imprecisely sourced pet-trade specimens.

[5] Turner and colleagues suggest that members of Brachypelma s.s. (their "red leg" group), which have small ranges and are slow to mature and reproduce, should be the focus of urgent conservation measures, with threats to species in the genus Tliltocatl (their "red rump" group) possibly being downgraded.