Any ladybird will tell you that it’s bad enough when an invasive species comes along and eats your supply of aphids, but what really annoys them is catching a sexually-transmitted illness from those very intruders. Unfortunately for the ladybirds of Britain, a larger Asian species is currently swarming the country, carrying with it a fungus that is passed on during mating.

Known as the harlequin ladybird, the species originates in China and Japan and is thought to have first been introduced to the UK as a natural pest control in 2004. Typically black with red spots and larger than most native British species, these prolific predators not only outcompete the locals for aphids, but also regularly eat the eggs and larvae of other ladybirds.

Yet the threat posed by these deadly trespassers doesn’t stop there, as they also carry the Laboulbeniales fungus, which can cover the exoskeleton of infected individuals. Fortunately for humans, our skeletons are inside our bodies, which means the fungus can’t affect us and there is no need to worry.

However, reports are emerging of large swarms of harlequins invading people’s homes, with populations currently booming. Like most ladybirds, the species hibernates during the winter in small cracks and crevices in trees or rocks, although gaps between house bricks or around loose-fitting windows will also do nicely.

With spring now beginning, the insects are emerging from their slumber – known as a diapause – which is why their presence is suddenly being felt so strongly in homes across the UK.

The best way to keep the ladybirds out of your home is to make sure all doors and windows are properly sealed. Meanwhile, the foreign harlequins are likely to continue to precipitate a drop in population numbers among native species, although this is expected to balance out at some point, and local ladybirds are unlikely to be totally wiped out by these Eastern invaders and their sexual fungus.

A similar scenario has already occurred in the US, where harlequin ladybirds were introduced around 25 years ago as a means of controlling aphid numbers, and have become established as one of the most common ladybird species in the country.