Changing Planet

Invasive Lady Beetle Kills Off Competition Using Parasites


A ladybug pileup. Photograph by Ed Young, Corbis

The Asian lady beetle (Harmonia axyridis)—a relative of the ladybug—was originally imported to the U.S. in 1916 in an attempt to naturally control pests. After escaping greenhouses, they spread uncontrollably throughout the U.S. and Europe in a matter of decades. But no one understood why they were such successful conquerors. (Related pictures: “Invasive Species in the United States.”)

Now, a recent study published in Science finds that Asian lady beetles contain tiny fungus-like parasites that infect and kill native species, wiping out the invaders’ competition for food.

Asian lady beetles are aggressive, known to attack the larvae and eggs of other insects like butterflies and native lady beetles with which they compete. But that’s not what makes them so deadly. The invaders themselves contain high concentrations of a fungal parasite called microsporidia.

“If one of the native lady beetles eats larvae and eggs of Asian lady beetles, [the natives] die off,” said Heiko Vogel, a biologist at the Max Planck Institute for Chemical Ecology and co-author of the study. (Related: “How a Cat-Borne Parasite Infects Humans.”)

“We were wondering, ‘What was going on there?'” he added.

Alien Invader

Vogel and his team identified Asian lady beetles from 12 different countries using physical examinations under a microscope and DNA analysis. After confirming the species, the researchers analyzed the beetles’ blood in order to figure out what was infecting and killing native bugs.

That’s when they found the fungal parasite lying dormant within the invaders. While Asian lady beetles are immune to the parasites, other insects are highly susceptible to its deadly effects. (Learn about a fungus that controls ant brains.)

“We didn’t believe our results at first,” Vogel said. “We wouldn’t have dreamed that this parasite, this fungus, would be a problem for the native beetles.”

When another insect eats an Asian lady beetle, the parasites activate. Microsporidia penetrate the new host’s cells, siphoning off its energy in order to multiply. The parasites continue to replicate until they’ve completely taken over and killed their host.

Then the fungus produces spores, which can survive harsh environmental conditions while waiting for the cycle to begin again. Asian lady beetles naturally contain a high concentration of these spores.

“We found these huge amount of spores in the blood of the Asian ladybird beetles, and we’re like, ‘What the hell?'” Vogel said. “When you see something like this, usually the insect is dead.” (See photos of how a parasitic fungus takes over ant brains.)

The invaders are incredibly hardy insects. Asian lady beetles have a hyperactive immune system, which could be what’s protecting them from succumbing to the spores in their blood.


And these conquerors aren’t just a problem for other insects. Every winter, Asian lady beetles gather by the thousands to weather the cold temperatures inside any cave-like dwelling they can find—including houses. Vogel’s own mother walked outside four years ago to find thousands of the pests attached to the side of her house, attempting to force their way in.

“They’re trying to sneak into crevices,” Vogel said. “You can’t open a window anymore or you’ll have thousands inside.”

The Asian lady beetles en mass have been known to cause health issues for people prone to asthma. They also give off a horrible smell when they sense danger as a deterrent against predators. One smelly beetle is nothing more than an annoyance, but if you have thousands of them, the stench can be a big problem, Vogel said.

Any efforts to eradicate the beetle, which also feasts on agricultural crops like grapes and apples, are likely a waste of resources, the biologist added. The bugs are just too resilient to control.

“I don’t think we can do a lot against [the Asian lady beetles],” Vogel said. “They’re so successful, and they’re spreading so fast. There’s no stopping them.” (Learn more about invasive species.)

Mollie Bloudoff-Indelicato is a science journalist who loves em dashes, ’80s music and parasites. She has a master’s degree from the Columbia University Graduate School of Journalism with concentrations in science journalism, photography, and radio reporting. Contact her at, and follow her on Twitter at @mbloudoff.
  • Ima Ryma

    The Asian lady beetle is
    An example of human goof,
    Messing with Mother Nature’s biz.
    Imported to U.S. for proof
    That other pests could be controlled,
    Not really knowing how or why.
    Native insects, lo and behold,
    Get spores from ladies and do die.
    Now the ladies have set their sights
    On making human pests’ lives grim,
    Invading homes in smelly blights.
    Native bugs were just a prelim.

    How to make ladies go away –
    Something worse to think up and spray.

  • Sam

    We used to have quite the concentration at my house until the Box-Elder bugs took over. Now I see just a few Asain Lady Bugs a year, usually around spring for a week and then they disappear. Could the Box-Elder bugs be slowing forcing out the Asain Lady Bugs???

  • Catherine Lindenberg

    I am not a very “science-type” person, in fact it was my worst subject @ school. Ironically, I have worked in the science field for well over 20yrs and I have learnt so much and find this article very intriguing. My inquisitive mind now asks: “Could this process be happening in other natural beings, human beings even?” I know we don’t eat one another, at least the majority of us don’t, but just by contact via bodily fluids or simply contact in general maybe it could set off some kind of reaction to kick in such things as the horrible diseases that we acquire. Such as, “Cancer”, which I believe is in all of us, but not all of us will experience it’s cruel manifestation. Rereading this it does seem like waffling babble, but as I first said “I am not a science-type person”. Just curious and inquisitive….always questioning with why and what if’s. Thanks for reading, if indeed you didnt tune out. Cheers : )

  • Becky

    We use to have lady beetles but no longer We now have stink bugs. How do these two get along? I’m wondering if the stink bug has eaten the ladybugs or just scared them away.

  • Emma

    Interesting post. Having a picture of the subject of your post, Harmonia axyridis, rather than Hippodamia convergens would have been better though!

  • Emma

    Interesting post. Would have been great to have a picture of Harmonia axyridis (the subject of your post) rather than the native beetle, Hippodamia convergens.

  • cory

    I asked about this article because I was watching a special and it was about the Asian beetles and I believe that the Asian beetle is wiping out all of our lady beetles that used to be around here I remember as a kid which I am 34 years old that I could pick up lady beetles by the hundreds in my garden up in the orchard I used to play in its really sad that we had introduced them because the lady bugs were so much nicer prettier and did not stink then the stinking Asian beetlesI would like some information about how we are trying to preserve our lady beetles that we used to have if at all there is any effort to do that

  • Debra Palmer


  • Tony Brough

    Here is something strange I noticed about ladybirds, I get some that over winter in the frame of my bathroom window which is kept open all summer, I generally wait until the weather gets so cold I need to close the window then i collect them and transfer them to a box (with holes) and move them to the garage for the winter however this year I stuck an egg carton (six pack) on the windowsill inside the bathroom i cut a hole in one end and started transferring them to the carton and they immediately started to climb out until i managed to get around 20 or so in the egg box then they stopped escaping and a couple that had escaped were making their way back to the egg carton, , I got curious so emptied the contents of the catching box onto the window sill and then watched in amazement as around 50 ladybirds walked across the windowsill and into the egg carton ????? so what is going on, Do they communicate via sound or do they produce a scent the others can home in on,
    after 2 days I opened the box to find a mass of ladybirds probably around 100 all happily hibernating and not a one to be seen anywhere else in the room, How did they know to go to the egg carton ??

    • Andre Szejner

      Hi, I currently work with the native ladybeetle (Hippodamia convergens) and they have a similar aggregation behavior like the one you encounter, but the native do it outdoors. You are right in that ladybeetles communicate to tell other individuals to gather in one spot. The communication is via smell (pheromones and such) rather than sound. In the case with the native ladybeetle, they actually leave ‘footprints’ where they walk that other ladybeetles can smell from far, and follow it until they find the source. This leads to massive aggregations! Now you know how to maybe even lure them to specific places. Great observations!

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