False widow spiders 230 times more poisonous than native Irish spiders

Noble false widow spiders are up to 230 times more poisonous than native species in Irish homes, a study has shown.

A team of scientists at National University of Ireland, Galway (NUIG) found that not only is the venom much more potent than that of any common northern European spiders, the species is also able to adapt its attacking behaviour to prevail in different scenarios.

The researchers investigated the potency of the false widow spider’s venom in a bid to understand why it is so successful at spreading in towns and cities throughout the world.

The study, published in the international journal Toxins, also revealed false widows can make calculated decisions on whether to attack large or small prey depending on how much venom is left in their glands.

If little venom is available, they avoid large opponents that could injure them, and instead focus on small prey.

Scientists also discovered that in battle noble false widows do not inject venom randomly, but target the most innervated body parts of its enemy, where the neurotoxic venom is most efficient.

This may explain why this species can tackle animals much larger than itself, including lizards, bats, shrews and other spiders.

The noble false widow spider killed and ate 95% of its opponents during the study.

Originating from Madeira and the Canary Islands, the noble false widow spider (Steatoda nobilis) has the potential to become one of the world’s most invasive species of spider.

It was first reported in southern England in 1879. In recent decades it has spread to Scotland, Wales and Ireland.

The species has also spread globally across Europe, east Asia, North America and South America.

It has can cause a range of mild to severe symptoms in people who are bitten, but little is known about its impact on native species. 

Over the past five years, the team at the NUIG’s Venom Systems Lab, led by Dr Michel Dugon, studied a range of characteristics specific to the species including its venom, symptoms after envenomation, ecology and behaviour.

Dr Dugon said: “Over the years, we have learned a lot about the noble false widow and its venom.

“This study is another important step to understand the true impact this species has on the ecosystems it invades throughout the world.”

Co-senior author Dr John Dunbar described the noble false widow spider as a “truly remarkable animal”.

“At every turn this species has surprised us in its ability to become globally invasive and dominate habitats it occupies,” he said.

“The tiniest amounts of venom – about 1,000th of a raindrop – can cause medically significant symptoms in humans that are about 250,000 times larger than them.

“Each new study brings us closer to understanding how exactly they are achieving their success.”