Texas Brown Tarantula (Aphonopelma hentzi)

Physical description and identification

The Texas brown tarantula is a heavy-bodied, thickly furred mygalomorph that looks larger than it measures, because the long hair on the legs blurs its outline. In daylight it is a uniform dark chocolate brown; in low sun the carapace throws back a coppery or rust-colored sheen, the single most useful field mark for the species.

Adults

• Size: mature females have a body 40–55 mm long and a leg span normally 90–110 mm (3.5–4.3 in). Exceptional females approach 125 mm across, but the 14–15 cm figures that circulate online sit well beyond what this species reaches. Males match the body length but have long, thin legs and a shrunken abdomen.
• Color: dark brown to nearly black legs and abdomen, the carapace a shade lighter and washed with rusty orange hairs. Freshly molted animals are darkest; by season's end the abdomen may look bald in patches where defensive hairs have been kicked off.
• Eyes and fangs: eight tiny eyes sit packed on a raised tubercle at the front of the carapace, and the spider sees poorly, relying on touch and vibration. The fangs swing downward and backward in parallel rather than pinching sideways — the mygalomorph pattern. Mature males also carry swollen pedipalps and hooked spurs under the first legs, used to hold a female's fangs open during mating.
• Urticating hairs: like all New World tarantulas, A. hentzi has a patch of barbed defensive hairs on the abdomen. When harassed it braces and rubs them off with the hind legs, throwing a cloud at the attacker. They are not venomous, but they lodge in skin, eyes and airways and itch for days. Old World species such as the orange baboon tarantula have no such hairs and bite instead.

Eggs and egg sac

A female mated in autumn stores the sperm over winter and builds her sac in late spring, four to five months after mating. She lays several hundred eggs — clutches of roughly 500 to 1,000 are typical for a large female — onto a silk mat, wraps it into a white cushion and turns it inside the burrow for about 45 to 60 days.

Spiderlings

Hatchlings are pale fawn and a few millimetres across. They stay in the mother's burrow for days to a couple of weeks, then disperse on foot to dig starter burrows no wider than a pencil. Growth is slow: a female needs roughly eight to ten years of annual molting to mature, and she keeps molting for life, which is why old females regrow lost legs.

The burrow and hunting

Texas brown tarantulas build no snare web. They dig a silk-lined burrow 15–40 cm deep in firm prairie soil, or move into an abandoned rodent hole or a crack under a rock. A thin apron of silk at the entrance — the sheet older accounts call a hammock — works as a trip line, carrying the vibration of a passing cricket down to the waiting spider, which lunges from the burrow mouth after dark. The same tunnel, plugged with silk and soil, is how the species survives Plains winters.

Where the Texas brown tarantula lives

Aphonopelma hentzi is the most widespread tarantula in the United States. Confirmed populations run from Texas and eastern New Mexico north through Oklahoma, Kansas and southeastern Colorado, and east into Arkansas, Missouri and northern Louisiana. This is the tarantula behind the famous autumn road crossings on the southern Plains.

Its habitat is open country with soil it can dig in: shortgrass and mixed-grass prairie, rocky hillsides, mesquite scrub, canyon rims and pasture edges. It avoids heavy shade and waterlogged ground. Burrows cluster where the soil suits, so one roadside bank may hold dozens while the field behind it holds none. Tarantulas never colonise houses, though a wandering male may end up in a garage or a swimming pool. Several close relatives share this range, including the Texas tan tarantula and, farther west, the desert tarantula; the genus page for Aphonopelma and the wider tarantula guide cover the group.

Are Texas brown tarantulas venomous?

Yes — every tarantula is venomous, and A. hentzi uses venom to kill the insects it catches. It is not medically significant to people. No death or serious systemic illness has ever been attributed to a North American Aphonopelma bite, and the venom has none of the neurotoxic or tissue-destroying components that make widow and recluse spiders dangerous. Our list of the most venomous spiders puts this species in perspective.

Can a Texas brown tarantula bite?

It can, but it very rarely does. A disturbed tarantula runs first; if cornered it rears onto its hind legs with the fangs exposed, a bluff that usually ends the encounter. Kicking urticating hairs is the next step. Biting is the last resort, and it happens almost only when the spider is grabbed or pressed against skin.

A bite feels like a deep pinprick or a bee sting. The fangs are large enough to leave two visible punctures, and that mechanical damage is often the worst of it. Expect local pain, redness and mild swelling for a few hours, occasionally a day. Wash the punctures with soap and water, apply a cold pack, keep the limb still and take a simple painkiller if needed. Seek medical care if the wound becomes hot, spreading and more painful after 24 hours, which suggests bacterial infection rather than venom, or if hives, breathing difficulty or faintness develop, which indicate an allergic reaction. Do not cut, suck or apply heat to the wound.

Ecological importance and behavior of the Texas brown tarantula

This is an ambush predator with an extremely low metabolic rate. An adult female may eat only a few dozen insects in a year and can survive months without food, which is exactly why she can afford to sit in one burrow for decades. Prey is whatever walks past: crickets, grasshoppers, beetles, cockroaches, centipedes, millipedes, other spiders and the occasional small lizard.

Natural predators: the most specialised is the tarantula hawk, a large spider wasp of the genera Pepsis and Hemipepsis. The female hunts the tarantula at its burrow, paralyses it with a sting, drags it into a chamber and lays a single egg on it; the larva eats the living but immobile spider. Older accounts call the wasp parasitic — parasitoid is the accurate term, since the host always dies. Coyotes, skunks, roadrunners, owls and snakes also take tarantulas, and vehicles kill far more than any predator.

Prey–predator dynamics: because burrows are fixed and long-lived, a healthy population removes a steady share of large ground insects year after year, and abandoned burrows are reused by beetles, scorpions and lizards.

Seasonal behavior: the striking event in this species' year is the male walk. After his final molt a male leaves his burrow for good and spends the rest of his life searching for females, typically from late August into October, when hundreds may cross a single stretch of highway in an evening. These are not migrations — the males are not going anywhere in particular, and none return. A male rarely survives the following winter, while the female he mated with may live another twenty years.

Relationship with humans: harmless, slow and useful. If one turns up in a yard, leave it or coax it into a tall container and release it in open ground nearby. No property ever needs treating for tarantulas, and because the animals are so long-lived, removing adults has effects on a local population that last decades.

Similar spiders and how to tell them apart

Quick facts

Did you know?

• The species was described in 1852 by Charles Girard and honours Nicholas Marcellus Hentz, the French-American naturalist who wrote the first serious account of North American spiders.
• A tarantula's haemolymph doubles as hydraulic fluid. The legs have no extensor muscles; the spider straightens them by pumping fluid in, which is why a dead or dehydrated tarantula curls its legs beneath itself.
• Until a 2016 revision, the United States was credited with more than fifty Aphonopelma species. DNA and morphology together cut that to twenty-nine and confirmed A. hentzi as the widespread Plains species.

In summary, the Texas brown tarantula is a slow, long-lived prairie animal with a reputation it does not deserve. It bites reluctantly, its venom is unimportant to people, and its itching hairs are the only real hazard — while the burrow it holds for decades quietly removes a steady supply of grasshoppers and crickets from the grassland around it.