Harmonia axyridis, the Asian Multicolored Lady Beetle
If I had to pick the most annoying insect in Illinois it’d be Harmonia axyridis. This lady beetle was introduced to our continent as a control agent for aphids but became a pest in its own right. It consumes not just aphids but all manner of other insects, including beneficials like native lady beetles. Swarms of them descend into our houses in the fall. They get just about everywhere. They have a noxious odor. And they bite.
A study out in PLoS One byLombaert et al has determined that our local beetles here in eastern North America are the culprit behind a spate of recent invasions elsewhere in the world. The researchers extracted DNA from 18 loci across the various populations, modeled several different introduction scenarios, and concluded that one story makes the observed genetic data the most likely. It’s this one:
Figure 1 from Lombaert et al 2010 showing the most likely path of introductions of H. axyridis.
The authors call this result “surprising”, but I disagree. If a pest builds to enormous numbers in a region that sees a lot of commerce, exports of that pest may become much more likely than exports from the native range. Especially if native populations are kept down by predators and competition.
We see this in ants all the time. The invasive Argentine ants in California arrived from an earlier invasion to the eastern U.S., not as a separate colonization from Argentina. Fire ants in Australia appear to be from the United States, not South America.
In any case, it’s an interesting and timely study. Now, if they could just figure out where I can send the beetles in my house so they don’t come back, that’d be really valuable.
source: Lombaert E, Guillemaud T, Cornuet J-M, Malausa T, Facon B, et al. 2010 Bridgehead Effect in the Worldwide Invasion of the Biocontrol Harlequin Ladybird. PLoS ONE 5(3): e9743. doi:10.1371/journal.pone.0009743
Myrmecos Blog 
It’s the most annoying insect in Missouri, too. It’s kind of apples and oranges to compare them, but I’d even venture they’re worse than mosquitos, all things considered. At least slapped mosquitos make good food for ants, and they don’t stink!
I’ve been finding these ladybugs in my house. How do they get in there? Why do they come inside in the first place? I’m having this problem now in Boston but my house back in Seattle used to get hordes of ladybugs inside the windows during spring and summer too. Very frustrating.
A couple years ago, i was at my parents house in central Wisconsin, and they had a building that had one side of it covered in these. Sadly i didn’t have a camera.
Send them to hell? Just kidding; I like these little bastards. Here in central Alberta, when the frozen grip of winter begins to thaw, these critters on my windows are the first signs of invertebrate life, and they cheer with the hope that winter, someday, will end.
You know Warren I was reading all the posts about I HATE these things, I was thinking YES, let’s annihilate these guys, Yeah! …and then I read your post. LOL love it! Thank you.
They have my vote as Second Most Annoying Insect, outranked by The Most Annoying Insect, Cluster Flies (Pollenia rudis). Both bug bastards invade my home every spring and fall, and really, don’t ever entirely leave. Ever. The flies win because they crap everywhere.
Why are they still legally being sold in the US? Shouldn’t the unsustainable concept of mono-cultural farming be allowed to die? It’s not like lady bugs are important for cereal crops, right?
Most widespread in southern Ontario, too. They are out of hibernation and invading homes again!
I agree that these are annoying and unwanted. Just another failure in exotic species introduction.
Here in the Ozarks, I’d have to rank M-CALBs third behind ticks and chiggers. I did find the information in your post “interesting”, though.
Now we have the South American stink bug, Piezodorus guildinii. This major pest of soybeans in Brazil has long been known in the U.S., from Florida to New Mexico, with never a mention as a pest. However, in the last few years, it has suddenly become the number one pest of soybeans from South Carolina to Louisiana. Major changes in cropping patterns? Maybe. New invasions of different genotypes? Researchable with molecular studies — in progress.