Carlsbad Green Tarantula (Aphonopelma gabeli)

Physical description and identification

The Carlsbad green tarantula is a large, thickset member of Aphonopelma, the genus that accounts for every native tarantula in the United States. Everything about it says ground: short powerful legs, a low body, dense dusty hair, and the downward-striking fangs and two pairs of book lungs that mark out the infraorder Mygalomorphae.

The common name misleads a little. Adults are brown to brownish grey, and the olive cast behind the word "green" appears only in some mature individuals and only in strong daylight, when the grey body setae take on a faint sage or bronze sheen.

Adults

• Size: a big Aphonopelma. Adult leg span is commonly around 11–15 cm (roughly 4½–6 in), with a body length near 4–6 cm. Females are heavier and broader in the abdomen; males are leggier and look far more fragile.
• Colour: brown-grey overall, with a coat of grey setae over the carapace, legs and abdomen and warmer rust or copper tones where longer hairs catch the light.
• Urticating hairs: the defining New World feature, and the one older accounts of this species usually leave out. The top of the abdomen carries thousands of tiny barbed setae that the spider rakes into the air with its hind legs when cornered — a mechanical defence, not a venomous one.
• Sexes: a mature male has swollen, club-shaped palpal bulbs, longer thinner legs, and tibial hooks on the front legs that hold a female's fangs apart during mating. A female never develops either.

Eggs and egg sacs

Mating happens in late summer and early autumn, when wandering males find a female's burrow. The female can store sperm for months and builds the egg sac later, deep inside her tunnel, wrapping the eggs in a thick disc of silk that she turns and guards continuously. Aphonopelma sacs of this size typically hold several hundred eggs.

Spiderlings

Hatchlings are pale and almost patternless. They remain in the mother's burrow briefly, then leave on foot — this genus does not balloon on silk — and dig thimble-sized burrows of their own within a few metres. Growth is slow even by spider standards: a female may need eight to twelve years of moulting to reach maturity. A leg lost to a predator regrows in miniature at the next moult.

The burrow and hunting

This species builds no snare web at all. Silk lines the burrow walls so they do not crumble, seals the entrance in the cold months and before a moult, forms the sheet on which a male deposits sperm, and wraps the eggs. Around the burrow mouth the spider lays loose lines that work as trip-wires: a beetle crossing them sends a tremor down the tunnel, and the tarantula rushes out, seizes it and drags it underground. Set beside the engineered snares in our guide to spider webs, a tarantula's silk is architecture and armour, never a trap.

Where the Carlsbad green tarantula lives

Aphonopelma gabeli is a Chihuahuan Desert animal. Its core range runs through southern New Mexico — the country around Carlsbad that gave it its name — west into south-eastern Arizona and east into the Trans-Pecos region of west Texas, with the same desert continuing into northern Mexico. It is one of the twenty-nine Aphonopelma species recognised from the United States in the 2016 revision of the genus.

Within that range it wants firm, well-drained soil: creosote flats, desert grassland, limestone hillsides, arroyo banks and rocky bajadas. Burrows sit under a stone, a shrub or an agave, and one hillside can hold dozens spaced a few metres apart. The tarantula plugs its entrance with silk and soil through winter and the driest stretch of early summer, then reopens it when the monsoon rains bring the insects back. Neighbouring species follow the same template elsewhere in the southwest — the desert tarantula in the Mojave and Great Basin, the Texas brown across the southern plains and the Arizona blond in the Sonoran Desert.

Are Carlsbad green tarantulas venomous?

Yes, in the plain sense that the spider carries venom and uses it on insects. No, in the sense most people mean: the venom of Aphonopelma is not medically significant to humans or to pets. No death and no serious systemic illness has ever been attributed to any member of the genus, and no antivenom exists because none has ever been needed.

That is the central difference between New World tarantulas and their Old World relatives. African baboon spiders and Asian ornamentals such as Poecilotheria have no urticating hairs and defend themselves with potent venom that can cause hours of muscle cramping. The American lineages went the other way: a mild bite and a cloud of barbed abdominal setae.

Can Carlsbad green tarantulas bite?

It can, but a bite is the last item on a long list. A disturbed tarantula first tries to walk away or back down its burrow. If it cannot, it turns its abdomen towards the threat and kicks hairs. If that fails it rears up and spreads the fangs in a threat posture that is almost entirely bluff. Only a spider that is pinned, squeezed or grabbed actually strikes.

When it does, the effect is local: sharp pain like a bee sting, two puncture marks from fangs several millimetres long, some swelling and redness. The mechanical wound is usually the worst part. Wash the site with soap and water, apply a cold pack, and seek medical attention for signs of infection or for an allergic reaction rather than for venom effects. Never apply heat, cutting, suction or any home remedy.

Ecological importance and behavior of the Carlsbad green tarantula

This is a sit-and-wait predator with one of the smallest home ranges of any large invertebrate. An adult female may spend twenty years inside a few square metres, sitting at the burrow entrance after dark with her front legs on the silk lines and dropping out of sight at the first footfall.

Diet: beetles, crickets, grasshoppers, cockroaches, moths and whatever else walks past, centipedes, scorpions and smaller spiders included. A big female will take a small lizard on occasion. The claim that desert tarantulas routinely eat mice belongs to the giant South American birdeaters, and even there it is uncommon.

Natural predators: the specialist is the tarantula hawk wasp (Pepsis and its relatives), which stings an adult into permanent paralysis, drags it into a burrow and lays a single egg on the living body. Beyond that: coyotes, skunks, ringtails, badgers, roadrunners, snakes, lizards and parasitic flies.

Prey-predator dynamics: a hillside carrying dozens of burrows removes a considerable weight of insects every warm night, while the tarantulas themselves feed a guild of vertebrates and parasitoids. In an arid system with few other large invertebrate predators, they sit in the middle of the food web rather than at the top of it.

Seasonal behaviour: the year is built around water. Burrows stay plugged through winter and through the pre-monsoon drought, and adults can go months without eating. Males mature after roughly eight to ten years, abandon their burrows for good and walk by night through late summer and autumn looking for females — the origin of the tarantula "migrations" that make desert roads briefly famous each year.

Relationship with humans: harmless and genuinely useful. Encounters are almost always with a wandering male in autumn. The real pressures are roadkill in the walking season, vehicle damage to burrow slopes and collection for the pet trade, where Aphonopelma are valued precisely for being slow, placid and long-lived. Removing an adult female hurts a local population most, because replacing her takes a decade.

Similar tarantulas and how to tell them apart

Quick facts

Did you know?

• The species was described in 1995 by the British arachnologist Andrew M. Smith, and it came through the sweeping 2016 revision of United States Aphonopelma as a valid species while dozens of older names were sunk as synonyms.
• A bare dark patch on top of an adult's abdomen is not injury or illness. It is the record of its own defence — the spot the spider has repeatedly stripped of urticating hairs. It fills in again at the next moult.
• A moulting tarantula lies on its back for hours and looks convincingly dead. It is the most vulnerable moment of its life, and a spider handled at that point can be crippled permanently.

In summary, the Carlsbad green tarantula is a patient, decades-old resident of the Chihuahuan Desert whose "green" is a trick of light on grey hair. It builds no snare web, its bite is a painful inconvenience rather than a danger, and the sensible precaution around it concerns your eyes and its barbed abdominal hairs far more than its fangs.