For years, Australia’s most infamous spider, the Sydney funnel-web, was feared and revered as a singular menace. It’s officially the most venomous spider in the world, responsible for 13 recorded fatalities thus far. But now, an international team of scientists has uncovered a surprising twist: the Sydney funnel-web isn’t one species — it’s three.

Among them, one spider stands out, not just for its sheer size but for its unrivaled venomous punch. Meet Atrax christenseni, nicknamed “Big Boy.”

Not one but three

The discovery stemmed from years of curiosity about unusually large funnel-web specimens found near Newcastle, a city 150 kilometers north of Sydney. These spiders were brought to the Australian Reptile Park for venom milking, where researchers had the chance to take a closer look.

“When our international team of researchers ‘reopened the case’ on the Sydney funnel-web, we looked at fine morphological details and gene sequences across the region and found the species split into three distinct groups,” said Dr. Helen Smith, a spider biologist at the Australian Museum.

The team combined anatomical and DNA analyses, comparing newly collected spiders with specimens dating back to the early 1900s. The results were intriguing: the iconic Sydney funnel-web spider, long thought to be a single species (Atrax robustus), was actually composed of three species:

• The “classic” Sydney funnel-web (Atrax robustus): Found in the Sydney Basin and Central Coast, but with a much more limited distribution around Sydney than previously believed.
• The Southern Sydney funnel-web (Atrax montanus): Resurrected from obscurity, this species inhabits the Blue Mountains to the south and west of Sydney.
• The Newcastle funnel-web (Atrax christenseni): Dubbed “Big Boy” for its size, this spider is not only the largest but also the most venomous of the three.

“Our research uncovered hidden diversity among funnel-web spiders,” noted study co-author Dr. Stephanie Loria of the Leibniz Institute for the Analysis of Biodiversity Change (LIB). “None of these insights would have been possible without the use of historical collections and international collaboration.”

A Big Boy with a punchy venom

Atrax christenseni owes its name to Kane Christensen, a Central Coast spider enthusiast who first brought the Newcastle specimens to researchers’ attention. “The sheer size of the males, compared to the males of the other Atrax species, is simply astounding,” Christensen said. “I am deeply honored and accept it with great pleasure.”

This species, which is native to the Newcastle area, can grow about 2 centimeters in size (for males). While its size is slightly larger than other funnel-webs, that’s still petite compared to the largest spider in the world, the 28-centimeter, the goliath birdeater (Theraphosa blonde). Its venom, more potent than that of its Sydney and Southern cousins, makes this spider the most venomous spider in the world.

The research suggests that the Atrax lineage began diversifying around 30 million years ago, during the Oligocene. This timing coincides with shifts in Australia’s climate and geography, which likely shaped the habitats where these spiders thrived.

What This Means for Antivenom and Human Safety

The funnel-web’s venom contains potent neurotoxins, particularly delta-atracotoxins, which interfere with sodium ion channels in primates. It is often compared to the venom of other deadly creatures such as the box jellyfish and inland taipan, although the mechanisms of action and symptoms differ.

The Sydney funnel-web venom can cause severe symptoms, including muscle spasms, difficulty breathing, and — in extreme cases — death. Luckily, since the first funnel-web antivenom was introduced in 1981, there have been zero fatalities. Since then, the Australian Reptile Park’s venom milking program has been helping to produce doses of the life-saving serum.

The program houses more than 2,000 spiders that are milked on a regular schedule. But to keep up these numbers, they rely on donations from the public. Capturing funnel-web egg sacs, in particular, is indispensable to the initiative. Producing a vial of antivenom requires nearly 150 spiders, and each egg sac can carry 50 to 150 spiderlings.

In light of these new findings, the funnel-web antivenom could be further refined, so it remains effective across all three species. The researchers hypothesize that differences in the presence, quantity, or structure of delta-atracotoxins may exist among the species. However, the venom of A. montanus and A. christenseni has not been thoroughly studied, leaving the question of specific differences open to future research

The findings appeared in the journal BMC Ecology and Evolution.