Northern Tree Funnel-web (Hadronyche formidabilis)

Physical description and identification

Hadronyche formidabilis is the biggest spider in the family Atracidae and one of the largest mygalomorphs in eastern Australia. It has the standard funnel-web look — polished, hairless carapace, downward-striking fangs, long finger-like rear spinnerets — scaled up until the body alone is the length of an adult thumb. The species name is not an exaggeration: formidabilis is Latin for formidable.

Adults

• Size: females reach 40–50 mm in body length, well above any other funnel-web; males are smaller and lighter, typically around 30 mm, with longer legs. Leg span in a large female easily covers the palm of a hand, which puts it among Australia's biggest spiders.
• Colour: the carapace is glossy black; the abdomen, legs and chelicerae are dark brown. Many individuals show a distinct purplish or plum wash along the upper sides of the abdomen, which is a helpful field character in good light.
• Carapace shape: narrower and proportionally longer than in other members of the genus, in both sexes — a difference obvious when specimens are compared side by side.
• Males: a mature male carries a knobby spur on the tibia of the second leg pair. That spur, plus the swollen pedipalp bulbs, separates males of this species from the very similar Darling Downs funnel-web, Hadronyche infensa.
• Eyes and spinnerets: eight small eyes clustered on a low mound at the front of the carapace, and a pair of long, soft, finger-like spinnerets projecting beyond the tip of the abdomen. See spider eyes for how mygalomorph eye groups differ from those of other spiders.

Eggs and egg sac

The female produces round to oval eggs wrapped in a flattened, pillow-shaped white silk sac and keeps it deep inside her tree hollow, where she guards it until the young emerge. The sac is never exposed on the outside of the trunk.

Spiderlings

Spiderlings hatch inside the maternal hollow and stay there through their early moults, which in this species can be a long period. Large hollows sometimes hold a mother and several well-grown juveniles at once, an unusual degree of tolerance for a funnel-web. Dispersal happens on foot as juveniles, not at maturity, and growth to adulthood takes years of successive moults.

The retreat and trip lines

Despite the common name, there is no funnel-shaped snare. The spider lines a hollow, split or crevice in a living tree with silk, forming a tube retreat with a collar of silk at the mouth, and runs a few irregular trip lines out across the surrounding bark. It waits just inside with its front legs on those lines and rushes out when something crosses them. The web is a detection system, not a trap — the same architecture used by ground-dwelling funnel-webs, simply transplanted up a trunk. Our guide to spider webs explains how this differs from the sheet webs of unrelated funnel weavers.

Where the northern tree funnel-web lives

The species occupies a narrow strip of the eastern seaboard of Australia, from southeastern Queensland — the hinterland behind the Sunshine Coast and the ranges inland of Brisbane — south through the Northern Rivers district of New South Wales to roughly the Hunter River. That distribution gives it its alternative name, the Northern Rivers funnel-web.

It is a forest animal, tied to subtropical rainforest, wet sclerophyll forest and the moist gullies between them. The critical resource is a hollow in a living tree: a knot hole, a split limb, a rot pocket behind bark, a hollow spout. Occupied hollows have been found from ground level to around 30 metres up, and a single large old tree may house several spiders in separate cavities. Rotting stumps, hollow logs and stacked firewood are also used, which is where most human contact happens.

Because the species depends on mature hollow-bearing trees, it is far more sensitive to logging and land clearing than the ground-dwelling funnel-webs, and it is essentially absent from cleared farmland and suburbs. Encounters are mostly the result of people going into its habitat rather than the spider coming into theirs.

Are northern tree funnel-web spiders venomous?

Yes, and this is one of the most medically serious spiders in the world. Its venom, like that of the Sydney funnel-web, contains δ-hexatoxins — short peptides that lock voltage-gated sodium channels in nerve terminals open for too long, so nerves fire repeatedly and flood the body with acetylcholine and catecholamines. The result is the classic funnel-web picture: muscle twitching, drenching sweat, salivation, vomiting, racing heart, soaring blood pressure and, untreated, circulatory collapse and fluid on the lungs.

Two features make it especially dangerous. First, both sexes are hazardous. In Atrax robustus the male's venom is several times more toxic to primates than the female's, so the risk is concentrated in wandering males; in H. formidabilis female venom is also potent, so any adult of the species is a serious animal. Second, clinical reviews of funnel-web bites have found that this species produces the highest proportion of severe envenomation of any funnel-web on record — a larger share of its bites progress to full systemic illness than for the Sydney species.

Set against that, encounters are uncommon. The spider lives in trees in forested country rather than in suburban gardens, so despite its venom it has caused far fewer recorded cases than A. robustus. It belongs firmly on any list of the most venomous spiders in the world.

Can northern tree funnel-web spiders bite?

They can, and a cornered one gives ample warning first: it rears back on its hind legs, lifts the front pair and its palps, and holds its fangs high with venom beading on the tips. From that position it strikes downwards with considerable force and may strike repeatedly or hold on. The fangs are large enough to drive straight through a fingernail.

Symptoms and timing. The bite itself is immediately and severely painful, with visible fang marks. Systemic symptoms usually begin within about ten minutes to two hours — the older literature quotes 15 to 20 minutes, which is typical rather than a limit. Expect tingling or numbness around the mouth, twitching of the tongue and then other muscles, heavy sweating and salivation, watering eyes, goosefleshy skin, nausea, vomiting, abdominal pain, a fast pulse and markedly raised blood pressure. Confusion, breathing difficulty and collapse mark severe envenomation. Children deteriorate fastest.

First aid. Funnel-web bites are the exception among spiders in that pressure immobilisation is the correct treatment:

• Keep the patient still and lying down and call emergency services (000 in Australia) straight away.
• Bandage firmly over the bite with a broad elastic bandage, then bandage the whole limb from the fingers or toes upwards, as firmly as for a sprain.
• Splint the limb so it cannot bend.
• Do not wash the bite, cut it, suck it, apply a tourniquet or give alcohol.
• Contain the spider safely if possible so it can be identified in hospital.

Antivenom. The funnel-web antivenom developed for Atrax robustus and released in 1981 also neutralises Hadronyche venom, including that of this species, and is given intravenously in hospital. No death from any funnel-web has been recorded in Australia since it became available. Bites remain emergencies, and the outcome depends on how fast the patient is bandaged and transported.

Ecological importance and behavior of the northern tree funnel-web

This is a long-lived, sedentary arboreal ambush predator. A female may hold one hollow for her entire adult life, enlarging the silk lining as she grows, sitting at the entrance after dark with her legs on the trip lines and retreating deep inside at the slightest disturbance.

Diet: beetles, cockroaches, crickets, moths, ants and other bark-dwelling invertebrates make up most of it, and a spider this size can also take small vertebrates — tree frogs and geckos are recorded prey. That places it near the top of the invertebrate food chain in the canopy and on the trunks of its forests.

Natural predators: birds, arboreal marsupials such as antechinuses, reptiles and centipedes take spiders that expose themselves, and parasitic wasps attack them in their retreats. Wandering males are the most vulnerable — see what eats spiders.

Seasonal behaviour and lifespan: activity peaks in the warm, humid months, when mature males leave their hollows at night to search for females. Older accounts giving this species a lifespan of ten to twelve months are wrong — that figure describes at most the short adult life of a male. Like other mygalomorphs the female takes several years to mature and then lives on for many more, probably well over twenty in some individuals, producing egg sacs across multiple seasons. Our guide to how long spiders live covers the pattern.

Relationship with humans: the species is dangerous but genuinely rare in contact terms, and it depends on exactly the mature hollow-bearing trees that logging and clearing remove. Protecting old-growth hollows protects the spider along with the possums, gliders and parrots that use them. Where a funnel-web is found near a house, it should be left alone or, if it must be moved, handled only with a long implement and a lidded container.

Similar spiders and how to tell them apart

Quick facts

Did you know?

• William Joseph Rainbow, the arachnologist at the Australian Museum, described the species in 1914 and placed it in Atrax; it was later transferred to Hadronyche.
• It is the only funnel-web whose females are considered as dangerous as its males, which reverses the rule of thumb people learn for the Atrax species.
• Occupied hollows have been recorded around 30 metres above the ground, making this one of the few mygalomorphs that routinely lives in the canopy.
• Clinical reviews of Australian funnel-web bites rank H. formidabilis as the species with the greatest proportion of severe cases, even though it bites people far less often than the Sydney funnel-web.
• Because it needs old trees with hollows, the spider is an indirect indicator of forest age: a stand with northern tree funnel-webs is a stand that has not been cleared in a long time.

In summary, the northern tree funnel-web is the largest and, dose for dose, the most reliably severe of the Australian funnel-webs, but it is a forest animal that most people will never meet. Keep gloves on when handling firewood and hollow timber in northern New South Wales and southeast Queensland, treat any suspected bite with a pressure immobilisation bandage and an immediate ambulance call, and leave the spider and its tree alone.