Ivory Ornamental Tarantula (Poecilotheria subfusca)

Physical description and identification

An adult female ivory ornamental is the biggest spider most people will ever see in the Sri Lankan hills, and one of the most ornate. The carapace is dark chocolate brown with pale margins and cream-coloured mouthparts, and the pattern radiating from its centre is often described as a starburst. The legs continue it in alternating cream and black rings. Held flat against lichened bark, all that contrast breaks the animal up completely; seen on a torch beam it is unmistakable.

Adults

• Size: females reach roughly 8–9 cm in body length and males 6–7 cm. Counting the legs, a large female spans about 15–18 cm, which makes this the biggest of the Sri Lankan ornamentals. Older accounts quoting 8–9 cm as the leg span are confusing body length with span.
• Females: the strongly patterned sex — dark carapace with pale edging, cream mouthparts, and legs banded in cream and black.
• Males: smaller and far plainer. After the final moult they are a fairly uniform pale to metallic brown above and below, with the female's starburst reduced to a faint ghost, and legs that are longer and thinner in proportion.
• Warning flash: as in the rest of the Poecilotheria genus, the undersides of the front legs carry bright bands that are hidden until the spider rears into a threat posture.
• No urticating hairs: this is an Old World tarantula. It cannot flick irritant hairs from its abdomen the way New World species can, so its defences are camouflage, speed and a bite.

Eggs and egg sac

The female lays bright orange eggs inside her retreat and wraps them in a thick silk sac, which she holds and turns and guards continuously. Because the whole process happens deep inside a tree hollow, wild egg sacs are rarely seen.

Spiderlings

Hatchlings are a plain brown and already densely covered in setae, with no trace of the adult starburst. The pattern appears gradually over successive moults. Spiderlings are fast from the first instar and disperse early to cut their own silk tubes nearby.

The web and hunting

This tarantula spins no prey-catching web. It builds an asymmetric silk tunnel inside a tree hollow or deep bark fissure, with an apron of tripwire threads at the entrance that is usually only visible at night when the spider is out and the silk is fresh. It waits at the mouth with its front legs on the threads and crosses the gap in a single strike. See our guide to spider webs for how this differs from a true snare.

Where the ivory ornamental tarantula lives

Poecilotheria subfusca is endemic to Sri Lanka, where it is a spider of the central highlands. It is most often recorded in the montane and submontane forest belt around Kandy, Nuwara Eliya and the Knuckles range, at elevations where nights are genuinely cool, and it is also found in the older lowland forest below that belt.

Like every ornamental it depends on mature trees with hollows and deep bark fissures, and it readily uses the large shade trees of tea and spice estates as well as the timber of old buildings when forest is unavailable. That flexibility is the reason it is still reasonably often encountered, but it does not offset the loss of old-growth trees across the hill country. The IUCN lists the species as Endangered. Two other ornamentals share the island, the lowland Sri Lanka ornamental and the very restricted yellow-backed ornamental, but no two are known to share a tree.

Are ivory ornamental tarantulas venomous?

Yes, and this is a genus where the usual reassurance about tarantulas does not apply. Poecilotheria venom is treated in the clinical literature as medically significant, and the ivory ornamental is no exception.

Verified bites follow a consistent course. There is immediate, severe pain at the puncture, then — typically after a delay of several hours — intense muscle cramps that often spread far beyond the bitten limb to the chest, abdomen and jaw. Sweating, fatigue, headache and recurring waves of cramping can continue for days to more than a week. There is no antivenom for Poecilotheria venom and no death has ever been reliably attributed to it, but people have been admitted to hospital for intravenous pain relief and muscle relaxants. Saying the venom causes "severe localised damage" is misleading: it is not a tissue-destroying venom like that of a recluse, and the real problem is systemic cramping rather than a wound that rots.

Can ivory ornamental tarantulas bite?

They can, and they are agile enough that a bite usually happens before the person realises the spider has moved. The ivory ornamental is not aggressive — it is nocturnal, shy and strongly inclined to slip around the back of a trunk — but it is highly defensive once cornered. The sequence is run, then rear and display the banded undersides of the front legs, then bite. Some defensive strikes are dry, but nobody can count on that.

If you are bitten: get clear of the spider and stay calm. Wash the bite with soap and water, apply a cold pack, and keep the limb still and elevated. Photograph the spider if you can do it safely, because the genus matters to the clinician. Seek medical care promptly and say the bite was from a Poecilotheria: the cramps usually arrive hours after the patient has stopped worrying, so someone sent home feeling fine may deteriorate later. Treatment is supportive — strong analgesia, muscle relaxants, fluids and observation. Do not cut, suck, tourniquet or heat the wound.

Ecological importance and behaviour of the ivory ornamental tarantula

The ivory ornamental is a nocturnal ambush predator of tree trunks, taking crickets, roaches, moths, beetles and other night-active insects, with large females occasionally catching small geckos or frogs. In hill forest where much of the insect biomass travels up and down trunks after dark, a resident population of large arboreal spiders is a real check on it.

Natural predators: pompilid wasps specialise in theraphosids, and geckos, snakes, civets, macaques and forest birds take spiders caught in the open. Parasitoid flies and wasps attack egg sacs inside the retreat.

Prey–predator dynamics: the starburst pattern is camouflage rather than display. Pressed flat on lichened bark the spider dissolves into mottled shadow, and its instinct with anything large is to move out of sight. Mature males give up that safety to wander in search of females, which is when most are found — and when most are eaten.

Relationship with humans: encounters are uncommon, and a resident population in an estate tree is a sign of habitat still worth having. The pressures run the other way: felling of old trees removes the hollows the species needs, and demand from collectors has drawn on wild-caught animals. All Poecilotheria have been on CITES Appendix II since 2019, so cross-border commercial trade requires permits. In captivity this is a display species for experienced keepers, never one to handle.

Similar tarantulas and how to tell them apart

Quick facts

Did you know?

• Keepers still separate a "highland" and a "lowland" ivory ornamental, sold as P. subfusca and P. bara, distinguished by how complete the abdominal pattern is. Taxonomically the distinction does not hold: the World Spider Catalog treats both P. bara and P. uniformis as junior synonyms of P. subfusca.
• Small microhylid frogs, including Nagao's pug-snout frog, have been recorded sharing tree hollows with ornamental tarantulas in Sri Lanka. The working explanation is a trade: the frog is safe from predators beside a large spider, and it eats the ants that would otherwise reach the spider's eggs.
• This is a slow species. Spiderlings can take four to five years to mature into females that then live another decade, which is one reason a collected adult is so hard for a wild population to replace. See how that compares with other species in our guide to how long spiders live.
• "Parachute spider", the South Asian name for the genus, comes from an old belief that these tarantulas glide between trees. They cannot — but a falling one spreads its legs and controls the drop well enough to land on a trunk and run.

In summary, the ivory ornamental tarantula is the largest and most ornate of Sri Lanka's tree spiders: a dark, pale-edged carapace, cream-and-black ringed legs, and a long life spent inside a hollow trunk. It is also an Old World tarantula whose bite belongs in a doctor's hands, not on a bare palm.