Anasaitis milesae spider


Exotic spiders are making themselves at home in Britain, capitalising on international trade and a warming climate. From tiny jumpers to large and striking species, these newcomers are reshaping the arachnid landscape.

One remarkable discovery is the tiny jumping spider Anasaitis milesae, measuring just 3-4mm, identified on the Penryn campus in Cornwall. Its nearest relative resides in the Caribbean, indicating a long journey to British shores alongside 17 other non-native jumping spider species. Meanwhile, larger arrivals like the false wolf spider (Zoropsis spinimana) from the Mediterranean and the green-fanged tube web spider (Segestria florentina) from Bristol have also found their niche in Britain.

Around 50 non-native spider species have been documented in Britain, part of the 3,500 established non-native species, most of which hitchhiked on global trade routes. Despite their numbers, only 10-15% are considered invasive, causing environmental or human harm.

Helen Smith, a conservation officer for the British Arachnological Society, said: “Britain’s spider fauna, along with the rest of our wildlife, is changing more rapidly than ever before. As new, exotic species spread, particularly beyond urban areas, the chances of them impacting on less common native species increase.

“As well as competing for prey and for living spaces, these spiders may bring with them new parasites and diseases, an issue well known from invasive grey squirrels and crayfish but very poorly studied in spiders. Around 15% of our native spider species are already threatened with extinction as a result of habitat loss and climate change – in the future, non-native species could well add to the risks they face.”

Tylan Berry, an arachnologist, stumbled upon the new jumping spider during a bioblitz on the Penryn campus, a testament to Cornwall and Devon’s allure for new spider species due to their ports and mild climate.

“It is amazing that something can be hiding in plain sight,” said Berry. “It’s established on the campus and easy to find in good numbers, living and breeding, and it’s also been found in another ornamental garden 30 miles away.

“It’s a pretty little thing, and looks like a bit of old 1970s carpet – brown and white and patterned.”

Berry also uncovered a thriving population of the grey house spider (Badumna longinqua) in Plymouth.

“It’s incredibly well-established in Plymouth,” said Berry. “I was really taken aback. It’s spread over a 6km/sq area and in some places is the dominant species.”

Originally from New South Wales, Australia, this invasive species is rapidly spreading across Britain, preferring urban environments and establishing large colonies.

“It’s definitely got potential for causing a shift in the ecosystem,” said Berry. “But rather than predating on native spiders, I think they might just be competition for space.”

While exotic spiders may fuel tabloid headlines and arachnophobes’ fears, their impact on humans is minimal. The false wolf spider and the green-fanged tube web spider, though large and impressive, pose little threat beyond occasional, harmless nips.

Despite their nonchalance, these spiders are on the move. The false wolf spider has expanded its range westward to Somerset and northward to Newcastle since its first sighting in 2008. Their journey, facilitated by global shipping and unwitting hitchhiking in holidaymakers’ vehicles, underscores their adaptability and resilience.

Spider experts have a message: don’t panic. “Look out for these things, record them if you can, but be interested in them as well,” said Berry. “The more you learn, the more you understand about a species, and that’s a good way of getting rid of any fears or misinformation.

“These arrivals are just going to happen. There’s very little we can do to stop them. Tied in to the warming of the climate, different species can get a hold in particularly areas and change ecosystems quite quickly.”



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