Invaders From Your Garden

You may have experienced the swarms of ladybirds in green spaces around Leeds or perhaps in your home. It’s getting to the time of year that ladybirds, alongside other overwintering animals, are looking to hunker down for the winter and hibernate. This is why they gather in large numbers, aiming to find a protected, warm spot like your windowsill!

Although, most of these ladybirds are not our native species but the invasive harlequin ladybirds (Harmonia axyridis), which arrived in the UK in 2004. It is thought they were introduced from Europe or the US as a natural form of pest control as they eat aphids, an aggressive herbivore of crop plants. However, the harlequins originally come from eastern Russia, China and Japan. You can identify the invasive Harlequin ladybirds by their orange legs, whereas our native species have a black body.

The harlequins often predate upon our native ladybirds and can also give them sexually transmitted diseases (STDs). This disease is caused by a fungus that lives on their exoskeleton and can be visible with the naked eye. However, there is no concern of this STD being transmissible to humans, so no need to worry!

Other invasive species, however, are very problematic throughout the UK. One such invader is the signal crayfish, Pacifastacus leniusculus, which was introduced to the UK in the 1970s as a food source. However, as a smaller member of the crustacean family, it turns out you don’t get much meat from crayfish. Therefore, many have been released into the wild where they have established large populations very successfully. They are such effective invaders because they breed rapidly and aren’t picky eaters; you may have spotted them in rivers or reservoirs and are often caught accidentally by fishermen.

Due to the UK’s temperate climate and poor border control, there are lots of well-established invaders including the Grey squirrel, Giant hogweed and the Asian hornet. It is also theorised that with climate change, the UK will become home to more invasive species as their thermal ranges shift northwards with the warming climate.