Wessel's Tiger Ornamental Spider (Poecilotheria tigrinawesseli)

Physical description and identification

Wessel's tiger ornamental is a large, flattened, tree-dwelling tarantula in the genus Poecilotheria, described only in 2006 and known from a small area of the Eastern Ghats in India. It is among the biggest members of the genus, and one of the most strongly marked on the legs.

The back carries the usual ornamental mosaic — tan, buff, brown and black arranged in a pattern that mimics lichen-covered bark. The legs are what separate it. The first pair is boldly yellow and black, and the fourth pair is a distinctive bluish slate-grey banded with black, a combination not seen in the other Indian species.

Adults

• Size: a large species. Adult females reach a leg span of roughly 20 cm (8 in) and males about 18 cm (7 in), with female body length around 7–8 cm. Males are lighter and proportionally longer in the leg.
• Colour: tan to brown overall with darker markings, the abdomen carrying a pale central band edged with dark chevrons. The yellow-and-black first legs and slate-blue fourth legs are the quickest field characters.
• Ventral flash: as in all ornamentals, the undersides of the front legs carry bold warning bands that are invisible while the spider walks and are displayed only when it rears.
• Body shape: carapace and abdomen strongly flattened, legs splayed outwards — built to disappear into a crack in heartwood.
• No urticating hairs: an Old World tarantula, so unlike a New World pinktoe it cannot flick barbed abdominal hairs. Speed, camouflage, a rearing display and the fangs are all it has.
• Sexes: mature males are slimmer, longer-legged and carry swollen palpal bulbs; many dull after the final moult.

Eggs and egg sac

The female builds her egg sac from dense silk inside the retreat she has spun in a tree cavity, and she guards it there rather than carrying it. Sacs hold one to two hundred eggs and take several weeks to develop.

Spiderlings

Spiderlings emerge pale and plainly marked, gaining the adult pattern and the banded legs over successive moults. Growth is fast for a tarantula: a juvenile can reach around 7 cm across the legs within its first year. They disperse to their own crevices within days of leaving the sac, and females take two to three years to mature.

The web and hunting

It is often written that this spider makes no use of silk. That is not accurate. What it does not build is a capture web — no sheet, no orb, nothing that traps prey. It does build a dense silk tube inside a hollow trunk or behind loose bark and runs silk lines out over the surrounding surface. Those lines carry vibration to the waiting spider, which sits at the retreat entrance after dark and crosses the bark in a fraction of a second when a moth lands. See our guide to spider webs.

Where Wessel's tiger ornamental spider lives

The species is endemic to India and, as far as current records go, to a small part of the Eastern Ghats in Andhra Pradesh — the hill country around Anantagiri and the Araku valley, which is the source of its other common name, Anantagiri's parachute spider.

Older profiles describe the habitat as "arid, dry regions". That is wrong and worth correcting: this is a hill-forest animal. The Anantagiri range carries moist deciduous and semi-evergreen forest, with coffee and fruit plantations among the remaining woodland, and the tarantula lives in hollow trunks, heartwood splits and gaps behind loose bark on mature trees there. It is sometimes found in the timbers of outbuildings on the forest edge.

Its range is small, its habitat is patchy, and the old hollow-bearing trees it depends on are exactly the ones removed when forest is cleared or plantations are replanted. The whole genus went onto CITES Appendix II in 2019, which regulates international trade, but forest loss remains the greater pressure.

Is Wessel's tiger ornamental spider venomous?

Yes, and the widely repeated claim that its bite is "not medically significant" is mistaken. Most tarantula venoms are of little consequence to people, but Poecilotheria is one of the few theraphosid genera that clinical toxicologists treat as genuinely significant, and there is no reason to think this species differs from its close relatives.

The characteristic effect is delayed muscle cramping. Sharp pain at the bite is followed hours later — sometimes after the local pain has already settled — by severe spasms in large muscle groups such as the calves, thighs, chest wall and abdomen, usually with sweating, headache and a general feeling of illness. The cramps come in waves and can persist for days.

No fatality has ever been recorded from any Poecilotheria bite, there is no antivenom, and healthy adults recover fully. The venom causes no tissue destruction. Other Old World arboreal tarantulas, such as the Asian earth tigers (Cyriopagopus), produce a broadly similar picture.

Can Wessel's tiger ornamental spider bite?

It can. The temperament is genuinely shy — confronted, the spider's first move is to bolt into its retreat or around the far side of the trunk, and its second is a rearing threat display with the fangs and banded legs exposed. But this is a very large, very fast spider with no urticating hairs to use as a warning shot, so a cornered individual escalates to biting quickly, and bites are often repeated rather than single.

In the pet trade this is regarded as an advanced arboreal species, kept in a tall ventilated enclosure with a vertical cork bark retreat and never handled. Handling is not part of responsible husbandry for any Old World tarantula.

Ecological importance and behavior of Wessel's tiger ornamental spider

This is a nocturnal ambush predator that spends most of its adult life attached to one tree cavity. The day is spent wedged inside the silk tube; at dusk the spider moves to the entrance and rests its front legs on the silk lines outside, reading the bark for movement.

Diet: large insects of the trunk and canopy — beetles, cockroaches, crickets, grasshoppers and moths. Big females will occasionally take a small gecko or frog, but such records are exceptional rather than typical.

Natural predators: the specific predators of this species are poorly documented, but across the genus the list is consistent — spider-hunting wasps, monitor lizards, snakes, civets, mongooses and insectivorous birds. Wandering mature males are the most exposed; a female deep inside a hollow is hard for anything to reach.

Ecological role: a resident adult removes large insects from a single tree year after year and in turn feeds the wasps and vertebrates of the same forest.

Seasonal behaviour: males mature after two or three years, leave their retreats and wander in search of females around the monsoon. They rarely survive a year past that final moult, while females may live a decade or more in the same cavity.

Relationship with people: encounters are uncommon and the spider never seeks one out. The sensible precaution in its range is not to reach blindly into a tree hollow, a woodpile or a dark roof space.

Similar spiders and how to tell them apart

Quick facts

Did you know?

• The British arachnologist Andrew Smith described this species in 2006, making it one of the most recently named members of a genus first erected by Eugène Simon in 1885.
• The epithet tigrinawesseli combines a reference to the tiger-striped legs with a dedication to the collector whose material led to the description.
• "Parachute spider" describes what a startled ornamental does when it leaves a trunk: it drops with all eight legs spread and uses its flattened body to slow and steer the fall.
• Individuals of different sizes are sometimes found in one hollow tree. That reflects an abundance of separate crevices rather than sociality — ornamentals remain solitary and will cannibalise one another.

In summary, Wessel's tiger ornamental is a large, beautifully camouflaged tree tarantula with a very small Indian range, a shy disposition, no urticating hairs and a bite capable of causing days of severe muscle cramping. It deserves distance and habitat protection in equal measure.