Some are small and bouncy; others are large and intimidating – if you’re a humble housefly. Exotic spiders are thriving in Britain as international trade provides ample opportunities for spiders and global warming provides an increasingly hospitable climate.
A jumping spider new to science has been identified as living on the University of Exeter’s Penryn campus in Cornwall. The closest known relative of the 3-4mm long Anasaitis milesae is found in the Caribbean, making it highly likely that this tiny species – along with 17 other non-native jumping spider species – found its way to Britain from distant regions.
Much bigger and more eye-catching new arrivals include Zoropsis spinimanacommonly known as the false wolf spider, a Mediterranean species that thrives in homes across London, and the striking greentooth tube web spider (Segstria florentina), which first gained a foothold in Bristol and is now found across southern Britain.
Around 50 non-native spiders have been recorded in Britain among 3,500 non-native established species, most of which have been accidentally introduced through the global movement of goods and people. Only about 10-15% of non-native species are considered “invasive” – such as gray squirrels, Japanese knotweed and the Asian or yellow-legged pear – causing a negative environmental or human impact.
Helen Smith, a conservation officer for the British Arachnological Society, said: “Britain’s spider fauna, along with the rest of our wildlife, is changing faster than ever before. As new, exotic species spread, especially outside urban areas, the chances of them having an impact on less common native species increase.
“Besides competing for prey and living spaces, these spiders can also introduce new parasites and diseases, an issue well known from invasive gray squirrels and crayfish, but very poorly studied in spiders. About 15% of our native spider species are already threatened with extinction due to habitat loss and climate change – in the future, non-native species may add to the risks they face.”
The new species of jumping spider was discovered by Tylan Berry, Devon and Cornwall area organizer for the British Arachnological Society, during a “bioblitz”, or biological census, on the Penryn campus. The unusual species was confirmed as new to science and named by Dmitri Logunov, a jumping spider expert, from the Zoological Institute of the Russian Academy of Sciences.
“It’s amazing that something can hide in plain sight,” Berry said. “Established on campus and easy to find in good numbers, living and breeding, it was also found in another ornamental garden 30 miles away.
“It’s a nice little thing, and looks like a bit of an old 1970s carpet – brown and white and patterned.”
Cornwall and Devon are hotspots for new spiders, thanks to their harbors and mild climate, with the absence of frost in some areas allowing alien species to survive the British winter.
Berry has a large population of another non-native spider, the gray house spider (Badumna longinqua) in Plymouth.
This large spider is native to New South Wales, Australia, and is considered one of the most invasive spider species in some countries where it has been accidentally introduced, including Japan, the USA and Brazil.
The fast-spreading species is not yet well established in mainland Europe, but has moved rapidly across Britain since it was first spotted in 2021. Since being found in Washington, north-east England, it has been recorded in South Wales, Nottinghamshire and Camborne and Newquay in Cornwall. Many early sightings were near ports or garden centers, suggesting they arrived on imported plants.
“It’s incredibly well established in Plymouth,” Berry said. “I was really amazed. It is spread over an area of 6 km/sq and is the dominant species in some places.”
The spider lives in large aggregates in urban areas, and weaves webs similar to some native spiders on wooden fences and metal signposts, including bus stops.
In places, Berry found only this species and few native spiders, and fears that they are native lace web spiders and missing sector orb weaver spiders.
“It certainly has potential to cause a shift in the ecosystem,” Berry said. “But rather than predating on native spiders, I think they might just be competition for space.”
Exotic spiders excite tabloid editors and alarm arachnophobes, and the false wolf spider and the green-toothed tube-web spider have the potential to cause a stir due to their size and their ability, in theory, to pierce human skin with their (briefly painful, but harmless) nips.
In reality, despite the media attention, the false wolf spider has caused little alarm and the green-toothed tube-web spider keeps to itself, living in holes in walls and darting out only at night to grab its prey.
Both species are on the move, with the false wolf spider spreading as far west as Somerset and as far north as Newcastle since it was first photographed in Britain in 2008 – in some cases given a lift, not only not on global shipping containers, but inside caravans of holidaymakers returning from mainland Europe.
Spider experts have a message: don’t panic. “Look out for these things, record them if you can, but also be interested in them,” Berry said. “The more you learn, the more you understand about a species, and it’s a great way to get rid of any fears or misinformation.
“These arrivals are just going to happen. There is very little we can do to stop them. Tied to the warming of the climate, different species can gain a foothold in particular areas and ecosystems change quite quickly.”
