Asian Ladybug Uses Its Own Biological Weapons to Best Competition

Research on the Asian lady beetle has shown why the species is able to thrive so successfully in every environment it is introduced to: its success relies on a form of insect biological warfare.

Commonly known as the Asian ladybird (or ladybug in North America), the Asian lady beetle was originally introduced to the U.S. and Europe as a form a pest control because of their capability eat as many as 200 aphids a day. The species has proliferated exponentially and some researchers fear that the Asian lady beetle will overtake native beetle species in some regions.  But until now, scientists have puzzled over why the dainty little bug could thrive amidst competition from other species.

It turns out the Asian lady beetle is the host to a parasite fungus that can be lethal when it comes into contact with other insects. The lady beetles are obviously immune to the parasite fungus, known as microsporidia, but many of the creatures the lady beetles come in contact with will meet a grim end.

The discovery that the lady beetles carry such a destructive toxin has offered scientist an explanation of why the Asian lady beetle population has expanded so greatly: they are killing their competition.

Growing numbers of Asian lady beetles have become a nuisance in some areas, where the insects congregate in large groups looking for hibernation spots in autumn. The bugs can sometimes cause a serious allergic reaction in humans. When prey becomes scarce, Asian lady beetles may feed on grapes. Consequently, they are often found on grapevines in vineyards in the fall. Once in the mash, the defensive chemical substances within the beetles negatively affect the taste of wine.

In addition to harboring toxins that wipe out competitors, the Asian lady beetles also have a helpful internal cocktail of antibiotics and antimicrobial peptides that enable them ward off illness more effectively than their native competition, which is often other types of aphid-eating beetles, especially other species of lady beetle.

 "The two-spot ladybird, a historically common and widespread species in Britain is suffering the most and experiencing dramatic and rapid declines," Helen Roy from the U.K.'s Centre for Ecology & Hydrology, told the BBC.

Heiko Vogel from the Max Planck Institute for Chemical Ecology, where the research was conducted, told the BBC that the future would likely be full of Asian lady beetles.

"I don't see any which way to stop them now - it's too late in my opinion," Vogel said.