Brazilian Black Tarantula (Grammostola pulchra)

Physical description and identification

The Brazilian black is the plainest of the large tarantulas and the easiest to recognise for exactly that reason. Every part of it — carapace, abdomen and all eight legs — is covered in dense, even, jet-black hair with a soft velvet sheen and no markings, bands or coloured fringe of any kind. In sunlight the coat can throw a faint bronze cast, but there is never a pattern to read.

Adults

• Size: the figure of 18 cm (7 in) often quoted for this species is the leg span, not body length. The body itself measures around 6–7 cm, and a mature female is a heavy, solidly built animal. Males are similar in span but much lighter.
• Colour: uniform black throughout. Juveniles are brownish or dark grey and darken steadily with each molt, so a young spider rarely looks like the adult it will become.
• Sensory hairs: the body carries fine trichobothria, hairs so sensitive to air movement and vibration that the spider detects prey and approaching predators without seeing them.
• Sexing: mature males carry swollen pedipalp bulbs and tibial hooks on the front legs; females stay bulkier and heavier. Before maturity the reliable method is examining a shed skin, not judging by size.

Eggs and egg sac

After mating the female takes roughly two to three weeks to produce a thick silk sac, which can hold several hundred eggs — figures up to about 650 spiderlings are reported for large females. She keeps the sac inside her retreat and guards it, turning it to keep humidity and temperature even, for six to eight weeks before the young emerge.

Spiderlings

Hatchlings are small, brownish and quick to dig: given loose soil, a threatened spiderling burrows rather than runs. Growth is famously slow. Where a salmon pink birdeater can approach adult size in two or three years, Grammostola pulchra takes four to eight years to mature, molting a few times a year as a juvenile and roughly once a year as an adult female. Our guide to spider molting explains what happens inside a shed skin.

The web and hunting

This species builds no capture web. It digs or occupies a burrow in the grassland soil, lines it with silk and lays a silk mat at the entrance that serves as a vibration sensor. After dark it waits at the mouth of the burrow, feels an insect cross the mat, and lunges. The silk is a tripwire and a home lining, never a snare.

Where the Brazilian black tarantula lives

Grammostola pulchra is a spider of the southern grasslands, not the Amazon. Its range covers the pampas and campos of southern Brazil — chiefly Rio Grande do Sul and Santa Catarina — and extends into neighbouring Uruguay. These are open, temperate landscapes of tussock grass, scattered shrubs and rocky outcrops, with warm summers and genuinely cool winters.

Within that country it is strictly terrestrial and fossorial, living in burrows under stones, at the base of grass clumps and along banks. Individuals are sedentary and may hold one burrow for years. The genus Grammostola occupies the same band of southern South America, and its neighbours include the Chaco golden knee, the Brazilian red rump and the Uruguayan black beauty tarantula — a close relative that causes most of the confusion around this species.

Are Brazilian black tarantulas venomous?

Yes, and harmlessly so. The venom of Grammostola pulchra is adapted to insects and has no documented medical significance for people. Clinical reviews of theraphosid bites place New World terrestrial species like this one at the mild end of the scale: local pain and swelling, nothing systemic, no antivenom, no recorded deaths.

Being a New World species, it also carries urticating hairs on the abdomen — barbed bristles it can rake off with the hind legs to irritate an attacker's skin, airway and eyes. What makes this species unusual is how rarely it bothers. It is among the most reluctant tarantulas to kick hairs, and it will normally retreat into its burrow instead. Its Old World counterparts, such as the king baboon tarantula, have no hairs to kick at all and compensate with far more potent venom.

Can Brazilian black tarantulas bite?

They can, but this is about as unlikely as a tarantula bite gets. The species is exceptionally placid: confronted with a threat it walks away, and if cornered it is more likely to turn its back than to rear up. Almost every documented bite has followed a spider being grabbed or pinned.

When a bite does happen, the venom is the smaller part of it. The fangs of a full-grown female are about a centimetre long and drive in deeply, so the injury is two puncture wounds with sharp immediate pain, some bleeding, and redness and swelling that settle within a day or two — the common comparison to a bee sting is fair for the venom, but understates the mechanical damage. The realistic complication is a local skin infection at the puncture site.

Wash the wound thoroughly with soap and water, apply a cold pack and keep the limb raised; an over-the-counter painkiller is usually all that is needed. Get medical advice if the site becomes hot, increasingly painful and red after a day or two, if swelling spreads, if you develop breathing difficulty or a widespread rash suggesting an allergic reaction, or if hairs may have reached an eye. Do not cut or suck the wound, and avoid home remedies.

Ecological importance and behaviour of the Brazilian black tarantula

In the southern grasslands this is a long-lived, sedentary ambush predator. It hunts at night from its burrow mouth and takes whatever large arthropods walk past: crickets, grasshoppers, beetles, cockroaches and other insects make up the great bulk of the diet, with small lizards and frogs taken occasionally when the chance arises. The rodents and "pinky mice" sometimes listed as food for this species reflect a captive feeding practice rather than its natural diet, and vertebrate prey is neither necessary nor typical. It can subdue prey up to roughly its own size, but the claim that it regularly takes animals twice its size does not hold up.

Natural predators: grassland birds, snakes, lizards and small carnivorous mammals take adults that are caught in the open. The specialist threat is the parasitoid spider wasp, which paralyses a tarantula with a sting, drags it into a burrow and lays a single egg on it.

Prey–predator dynamics: because an adult female may hold one burrow for twenty years or more, a single spider exerts steady, low-level predation pressure on the same patch of grassland for decades. Very large clutches offset a very high death rate among dispersing spiderlings.

Relationship with humans: the species is harmless and is rarely met, since it stays underground. Its docility and long life have made it heavily sought after in the international pet trade; captive breeding now supplies that demand, which matters because a species that takes up to eight years to mature recovers from over-collection very slowly.

Similar spiders and how to tell them apart

Quick facts

Did you know?

• The species was described in 1921 by the Brazilian zoologist Cândido Firmino de Mello-Leitão; pulchra is Latin for beautiful.
• It is often called the black Labrador of the tarantula world, a nickname earned by a temperament that runs to retreat rather than threat display.
• Four to eight years to adulthood is extraordinary even among tarantulas, and a female that reaches thirty years old has spent most of her life in a single burrow.
• The jet-black coat is not pigment in the cuticle alone but a dense layer of hairs; a freshly molted spider is at its blackest and slowly dulls as those hairs wear.
• Being a mygalomorph, it belongs to the ancient spider lineage whose fangs strike downward in parallel, a group separate from almost every spider you find indoors.

In summary, the Brazilian black tarantula is a large, slow, jet-black grassland spider with mild venom, urticating hairs it seldom uses and a lifespan measured in decades. Identify it by what it lacks — no bands, no fringe, no pattern at all.