Category Archives: Invasive species in Britain

Mitten crabs in the Thames

Chinese mitten crabs are becoming increasingly common in the River Thames and other rivers in England, having arrived in ship’s ballast from Asia. Mitten crabs cause a great deal of damage by burrowing into and destroying fragile riverbanks. They prey on other species and compete with native animals such as crayfish. Continue reading Mitten crabs in the Thames

The most venomous spider in Britain

This title has been awarded to an invasive species, Steatoda nobilis, known as the Biting Spider or False Black Widow.  It first arrived in England around 1870 on a shipment of bananas from the Canary islands to Torquay. Its bite is likened to that of a Continue reading The most venomous spider in Britain

Harlequin Ladybird Population Explosion

The Asian Harlequin ladybird (Harmonia axyridis) is capable of devouring over 12,000 aphids a year.  This voracious appetite is why it was introduced to North America and then Continue reading Harlequin Ladybird Population Explosion

Midwife Toads in Britain

The Midwife Toad (Alytes obstetricans) might have lived in Britain for over a hundred years, but it is still officially an “alien” species.  The invasion of the toad began over a hundred years ago in a Bedfordshire nursery garden, as Christopher Lever narrates in “Naturalized reptiles and amphibians of the world”:

“The nursery garden belonged to the firm of Horton & Smart, by whom the toads are believed to have been introduced accidentally as eggs in a consignment of ferns and water plants from southern France.”

Offshoot colonies grew in York and Northamptonshire, but the stronghold of the Midwife Toad in England has remained in Bedfordshire.  The species is named for the nurturing behaviour of the male, who carries the eggs wrapped round its hind legs until they are ready to hatch.  This keeps them warm and protected from treacherous English frosts and unreliable weather.  Yet even after a century the Midwife Toad still has the capacity to puzzle and even frighten people when they hear its nocturnal “bleeping” song in their suburban gardens.