Invasive Ladybugs Use Biological Warfare On Native Species
May 17, 2013

Invasive Ladybugs Use Biological Warfare On Native Species

Brett Smith for - Your Universe Online

German researchers have uncovered another cautionary tale about the importation of a species that quickly becomes an invasive threat. Introduced to Europe and North America for the purpose of controlling pesky greenhouse aphids, the Asian lady beetle escaped into the ecosystem and quickly dominated the local ladybug population.

According to a new report in the journal Science, the aggressive ladybug´s dominance is being assisted by parasites being carried within its own bloodstream that are highly lethal to other species.

"They keep them inactive in their own blood, we don't understand how they do it yet," co-author Heiko Vogel from the Max Planck Institute (MPI CE) for Chemical Ecology told BBC News. "But when the other [ladybugs] start to attack the invader's eggs and larvae, they become active and kill the native ones."

When the German biologists looked at the Asian lady beetle's haemolymph, or blood, under a microscope, they were able to identify the tiny parasites: fungi called microsporidia. While the fungi are present in the eggs and larvae of the invasive species, they appear to exist in a dormant and harmless state.

However, when other ladybugs were exposed to the microsporidians in the lab, the colorful beetles all died within two weeks. Because ladybugs often eat each other´s eggs and larvae, native species are highly vulnerable to parasitic infection in the wild, the researchers said. Some are also suspecting a parasitic wasp that lays its eggs in various ladybug species as a form of transmission.

For the research team, it appears the excitement of the discovery is tempered by the idea that the invasive ladybugs are poised for world domination, albeit on a relatively small scale.

"I don't see any which way to stop them now - it's too late in my opinion," Vogel said. "The fascinating thing is they can survive in such a wide range of temperature zones, and they are starting to pop up in South Africa and South America."

The invasion has become so prevalent in the United Kingdom that scientists there are asking citizens to report sightings of the insects via a specially designed smartphone app.

While the Asian lady beetles are known to devour aphids at a ferocious rate, they have been observed switching to grapes in the absence of their favorite prey. The invasive species biochemical makeup has been known to affect the taste of wine if they become trapped in the production process.

"They go on apples and grapes and that is becoming an increasing problem because of the massive amounts of these beetles,” Vogel said. "The tainting of the wine with a single beetle is not funny!"

One aspects of the beetle that could affect the winemaking process and was initially suspected as the source of its dominance is its immune system. The ladybug´s bodily fluid contains a strong antibiotic compound called harmonine as well as antimicrobial peptides. These antibiotic devices are so powerful that pharmaceutical companies are racing to exploit them for drug development.

Some still suspect the immune system as a contributing force to the ladybug´s dominance, saying that they are less susceptible to the diseases and parasites that affect other species.