What do we know about these unknown jumping spiders that have just been spotted in Britain? – Evening edition West-France

What do we know about these unknown jumping spiders that have just been spotted in Britain? – Evening edition West-France
What do we know about these unknown jumping spiders that have just been spotted in Britain? – Evening edition West-France

International trade, coupled with global warming, offers opportunities for exotic species to travel to Europe. In recent months, Great Britain has spotted a “jumping spider” never before observed. Enough to make arachnophobes sweat. Explanations.

After the United States and their Joro, these invasive spiders from Japan that can measure around ten centimeters long, legs spread out, it is the turn of the British to communicate on a new exotic species discovered on their territory, relays the British daily The Guardian. A spider native to the Caribbean has just been identified after being spotted in 2023 on the Penryn campus in Cornwall, during a biological census organized by the British Arachnological Society. Arachnophobes can be reassured.

This is a tiny jumping spider (Anasaitis milesae) harmless, like the vast majority of spiders in the world, not exceeding 3 to 4 mm in length. “No one can say it’s an invasive species. Only scientific studies with population monitoring would make it possible to say this. Without these numerical data, there is nothing to confirm that through its way of life, this spider replaces another native species. explains to the evening edition Christine Rollard, arachnologist at the National Museum of Natural History in Paris.

Other species from far away

This is not the first spider to come from afar. Among 3,500 species present in Great Britain, fifty non-native species have become established in recent years, underlines the English newspaper. “Only 10 to 15% are considered invasive species, causing negative environmental or human impact,” estimates the Guardian.

Londoners, for example, are seeing people arriving in their homes more and more frequently. Zoropsis spinimana, better known as false wolf spiders, a Mediterranean species. Some do not hesitate to travel to see the country. First noticed in Bristol, the green-fanged tube-web spider (Segestria florentina) has, for example, now taken up residence in the south of the country. But don’t panic: despite their appearance which can make even the most phobic people sweat, they are harmless.
Another undesirable which is the subject of particular attention, because it makes specialists fear “a change in the ecosystem” : the gray spider (Badumna longinqua), coming from Australia. Accidentally also introduced into Japan, the United States or Brazil, this species is considered one of the most invasive species of spiders in these territories. While it has not yet become well established in continental Europe, this large spider has been detected in several regions of Great Britain since its first sighting in 2021.

Container travel

But how did they get there? Like the Asian hornet, international trade provides them with numerous travel opportunities. Most arrive via international shipping containers or in luggage. “In France, we occasionally find the Andalusian tarantula (Macrothele calpeiana), in garden centers or gardens. They arrive with olive trees imported from southern Spain,” adds French arachnologist Christine Rollard. With global warming, our environment would also become more and more hospitable to them, according to British specialists. In Great Britain, port regions with mild climates would thus be in the front line.

Read also : The Andalusian tarantula spotted in France, a specimen was captured in the Var

A danger for other species?

For Helen Smith, head of conservation at the British Arachnological Society, interviewed by British journalists, vigilance is necessary because native spiders are “already threatened with extinction due to habitat loss and climate change.” “In addition to competing for prey and living spaces, these spiders can also bring new parasites and diseases, a problem well known to gray squirrels and certain crayfish, but very little studied in spiders,” continues the scientist.

Nothing worrying for Christine Rollard. No disease has ever been transmitted by spiders! The arachnologist from the National Museum of Natural History in Paris is much more measured and cautious. She knows something about it. These species from far away also spread their web in France. “We occasionally find exotic species here, but not all of them settle down permanently. And if they do, like Zoropsis spinimana for example, a species that has moved further north from its original southern distribution over the past thirty years, no data validated to date allows us to suggest that they are replacing other species. »

There is therefore no question for her to use the terms invasion or colonization as some do. Arachnophobes can therefore sleep peacefully. Especially since“There are no more than 15 cases of death worldwide per year from spider bites”, recalls the French specialist who is always surprised by the fear that spiders arouse.

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