Hadronyche

Physical description and identification

Hadronyche is the largest and most widespread genus in the family Atracidae, the Australian funnel-web spiders. Where Atrax holds a handful of species around Sydney and the southern tablelands, Hadronyche holds more than thirty, spread down the whole eastern side of the continent and across into South Australia and Tasmania. The genus was described by the German arachnologist Ludwig Koch in 1873 — not, as is sometimes written, by an entomologist.

Members of the genus cannot be told apart from Atrax at a glance. Both are dark, glossy, thickset mygalomorphs with downward-striking fangs, and separating the two genera reliably needs microscopic characters of the spinnerets and the male palp. For anyone outside a laboratory the practical rule is simple: treat any glossy black Australian spider that rears with its fangs raised as a funnel-web, whichever genus it belongs to.

Adults

• Size: the genus spans an unusually wide range, from small species barely 10 mm in body length to Hadronyche formidabilis at 40–50 mm, the largest funnel-web of all. Females are always bulkier than males of the same species.
• Colour: black, dark brown or plum. The carapace is glossy and carries only sparse hair; the abdomen is duller, finely haired and sometimes washed with purple along the upper sides. No species carries stripes or bright markings.
• Eyes: eight small eyes packed on a low mound at the front of the carapace, none of them enlarged. Our guide to spider eyes explains how this differs from the arrangement in hunting spiders.
• Spinnerets: long, soft and finger-like at the rear of the abdomen, projecting well beyond its tip — the most useful family character in the field.
• Males: mature males have swollen pedipalp bulbs and, in most species, a spur on the second leg used to hold a female during mating. The shape of that spur and of the palp is what species identification rests on.

Eggs and egg sac

Females lay their eggs inside the burrow or tree hollow, wrapped in a flattened, pillow-shaped silk sac holding up to a hundred or so eggs. The mother stays with the sac, and hatching takes a few weeks. Sacs are never carried about or placed outside the retreat.

Spiderlings

Spiderlings do not leave immediately, contrary to a common claim. They remain in the maternal retreat through their first moults — weeks in some species, months in others — before dispersing on foot to dig their own burrows nearby. In the large tree-dwelling species a single hollow may hold the mother and several well-grown juveniles at once. Reaching maturity takes years, commonly four or more and longer in the biggest species, with each stage reached by a moult.

The retreat and trip lines

No Hadronyche builds a capture web. Each spider lines a shelter with silk — a burrow in soil or leaf litter for most species, a hollow or crevice in a standing tree for the tree-dwellers — and finishes the entrance with a collar of silk. From that collar run a few irregular trip lines across the surrounding ground or bark. The spider waits inside with its front legs on those lines and ambushes whatever crosses them. It is a tripwire and an alarm rather than a snare; see spider webs for how this compares with the sheet webs of the harmless funnel weavers and the true curtain-web spiders.

Where Hadronyche spiders live

The genus is endemic to Australia and occupies a far larger area than Atrax. Species occur from southern Queensland down the New South Wales coast and ranges, through the Australian Capital Territory and Victoria, into Tasmania, with a few species in South Australia. They are absent from Western Australia and the Northern Territory, so a large black spider in Perth or Darwin is not a funnel-web.

Habitat divides the genus in two. Most species are ground dwellers that burrow in cool, humid, shaded soil — under logs and rocks, in creek banks, rock crevices, deep leaf litter, rotting stumps and, in settled areas, rockeries, compost heaps and mulched beds. A smaller set, including H. formidabilis and the southern tree funnel-web H. cerberea, lives in hollows and splits in living trees, sometimes tens of metres above the ground.

What every species needs is moisture. Funnel-webs dry out quickly and cannot survive in exposed, sun-baked ground, which is why they cluster in gullies, on south-facing slopes, in forest and in old shaded gardens. Highland species such as H. alpina extend into genuinely cold country, and the Tasmanian species tolerate a cool maritime climate that no Atrax reaches.

Are Hadronyche spiders venomous?

Yes, and several species are capable of killing a person. Funnel-web venom acts through a family of peptides called δ-hexatoxins, which bind voltage-gated sodium channels in nerve terminals and stop them from shutting down properly. Nerves then fire repeatedly, releasing a flood of acetylcholine and catecholamines, and the patient develops the characteristic autonomic storm: muscle twitching, drenching sweat, salivation, vomiting, a racing heart and dangerously high blood pressure, progressing in severe untreated cases to circulatory collapse and fluid on the lungs.

Severity is not uniform across the genus. Species with a documented record of serious human envenomation include the northern and southern tree funnel-webs (H. formidabilis and H. cerberea), the Darling Downs funnel-web (H. infensa), the Blue Mountains funnel-web (H. versuta) and the Port Macquarie funnel-web (H. macquariensis). Others, including several small southern species, have caused only local effects in recorded cases. Because species cannot be told apart in the field, every bite is managed as though it came from a dangerous one.

One important difference from Atrax robustus: in the tree-dwelling Hadronyche species the female's venom is as dangerous as the male's, so the familiar advice that only the wandering male matters does not hold here. Several members of the genus appear on any serious list of the most venomous spiders in the world.

Can Hadronyche spiders bite?

They can, and a cornered funnel-web is quick to do it. The warning display is unmistakable: the spider rears onto its hind legs, raises the front pair and the palps, and holds its fangs high with venom beading on the tips. It then strikes downwards hard, often more than once, and may cling to the skin. The bite is immediately and severely painful and normally leaves two clear puncture marks.

Symptoms. Systemic effects, when they develop, usually begin within about ten minutes to two hours: tingling or numbness around the mouth, twitching of the tongue and then of other muscles, heavy sweating and salivation, watering eyes, goosefleshy skin, nausea, vomiting, abdominal pain, a fast pulse and steeply raised blood pressure. Confusion, breathing difficulty or collapse indicate severe envenomation. Children deteriorate faster than adults.

First aid — pressure immobilisation, which is correct for funnel-webs and wrong for most other spiders:

• Keep the patient still and lying down and call emergency services (000 in Australia) immediately.
• Bandage firmly over the bite with a broad elastic bandage, then wrap the whole limb from the fingers or toes upwards, as firmly as for a sprained ankle.
• Splint the limb so it cannot bend.
• Do not wash the bite, cut it, suck it, apply a tourniquet or give alcohol.
• If it is safe to do so, trap the spider in a solid, lidded container for identification.

Antivenom. The funnel-web antivenom developed by Struan Sutherland's team at the Commonwealth Serum Laboratories in Melbourne was released in 1981 — not 1980, as is often stated. It was raised against male Atrax robustus venom but neutralises Hadronyche envenomation as well, and it is given intravenously in hospital. No funnel-web death has been recorded in Australia since it came into use.

Ecological importance and behavior of Hadronyche spiders

Hadronyche spiders are patient, strongly territorial ambush predators that spend almost their whole lives within a body length of one entrance. A female enlarges and repairs a single retreat for years, emerging only at night to sit at the mouth with her front legs on the trip lines.

Diet: broader than the "insect larvae and wood-boring beetles" sometimes quoted. Beetles, cockroaches, crickets, millipedes, slaters, snails and ants make up the bulk, and the large tree-dwelling species also take tree frogs, geckos and small skinks. Across their range these spiders remove a considerable volume of ground and bark invertebrates every season.

Natural predators: birds, bandicoots, antechinuses and native rats, reptiles and centipedes take exposed spiders, and parasitic wasps paralyse them to provision their nests. Wandering males are the most vulnerable stage, as is true across the order — see what eats spiders.

Life cycle: maturity takes years, typically four or more and longer in the biggest species. Males then leave the retreat permanently, wander on warm humid nights in search of females, and die within months. Females live on, sometimes for two decades, producing egg sacs across several seasons — an unusually long life span covered in how long spiders live.

Relationship with humans: genuinely dangerous, genuinely valuable and, in the tree-dwelling species, genuinely threatened by the loss of mature hollow-bearing trees. Practical safety costs nothing: gloves and closed shoes for gardening and firewood work, no blind reaching under logs or into hollows, shaking out clothing and footwear left outdoors, and checking swimming pools, since a submerged funnel-web can stay alive for hours on trapped air.

Species in the genus and similar spiders

Quick facts

Did you know?

• The genus was described in 1873 by Ludwig Koch, one of the most prolific arachnologists of the nineteenth century and the son of another, Carl Ludwig Koch.
• Hadronyche venom has become a serious source of drug candidates. Hi1a, isolated from the Darling Downs funnel-web, is being investigated for protecting heart and brain tissue after a heart attack or stroke.
• The Blue Mountains funnel-web produced ω-hexatoxin-Hv1a, a toxin that blocks insect calcium channels while leaving vertebrates unaffected — the starting point for a commercial biological insecticide.
• Tree-dwelling species can occupy hollows tens of metres above the ground, which makes them among the very few mygalomorphs living high in a forest canopy.
• Funnel-web antivenom is made from the plasma of rabbits immunised against Atrax robustus venom, yet it neutralises Hadronyche envenomation too — a rare case of one antivenom covering an entire family.

In summary, Hadronyche is the funnel-web genus most Australians will actually encounter: thirty-plus species, ground burrowers and tree dwellers, spread from Queensland to Tasmania. Several are as dangerous as the Sydney funnel-web and some are worse, but one antivenom covers them all, and the combination of a pressure immobilisation bandage and a fast ambulance has kept the death toll at zero since 1981.