Monday, May 18, 2015

Apple #711: Do Ladybugs Bite?

If you've been reading the series of entries on how I put together these here Daily Apples, you'll already be a little bit familiar with this topic (I used this topic as an example in Part 2 of Behind the Daily Apple).  But it seems to me that the best way to finish the question, how do I do what I do, is to show you the final result.  So here is the final result.

So here's the question I said I would take up: what's up with the biting ladybugs?  To get a bit more specific, where did they come from?  Did they always bite, or is this a new thing?  Let me insert one more general question ahead of that: Do ladybugs bite?

  • Short answer: Yes. And it's kind of our own fault.

Asian ladybug. This kind bites.
(Photo from GardenWeb)
  • This is a case of unintended consequences. Or put another way, people not really thinking through the effects of their actions.
  • As early as 1916, again in the 1960s, and yet again in the 1970s, people in the US brought ladybugs from Asia here to this country because those Asian ladybugs ate aphids.  
    • What better way to control this pest problem? they said with excitement. No pesticides necessary!  We just drop a bag of Asian ladybugs on these pecan trees, or on these rose bushes (that's what the ladybugs were sold for in my home town, back in the day), and they'll eat up the aphids!  No more aphid problem!  Sure, maybe we've got a few extra ladybugs.  So what?  They're harmless.  They're ladybugs!
  • Well.  After enough years of dropping bags full of ladybugs onto pecan trees and rose bushes and whatever else, the Asian ladybugs made themselves at home here in this country.  They "jumped ship" as one source put it, meaning they did not die off at the end of the season but rather started building little ladybug homes, having little ladybug babies, and raising their offspring, who then went and had more little ladybug babies.

Multicolored Asian lady beetle females can lay up to 3,800 eggs in one season, sometimes in batches of 20 to 30 eggs per day.  Lots of ladybugs making lots of ladybug babies, and you'll get a pretty big ladybug population pretty fast.
(Photo from The Ohio State University OARDC)

  • They were "observed in the wild" -- meaning there was a large enough colony living on their own, outside of any farmer's or gardener's observation or assistance -- in New Orleans in 1988.  Since then, the Asian ladybug has spread like crazy across most of the United States and Canada.
  • They are now considered established in the Northwest, the Northeast, and the Midwest.
  • Why is this such a problem?  After all, they're only ladybugs, right?
  • To answer that, we have to know a little more about this particular kind of ladybug.
  • The Asian ladybug, a.k.a. . . .
    • Harmonia axyridis
    • multicolored Asian lady beetle
    • Asian lady beetle
    • Halloween lady beetle
    • Japanese lady beetle
    • harlequin ladybird
    • many-named ladybird
    • multivariate ladybird
    • pumpkin ladybird
    • Japanese ladybird
    • southern ladybird
  • . . . eats aphids.  I mean, they really go to town on the aphids.  They were first brought here to eat the aphids on pecan trees, but then they discovered all the soybean fields all across the south and the Midwest.  Rife throughout those soybean fields were soybean aphids.  A smorgasbord to the multicolored Asian lady beetle.  And they went to town, munching up the soybean aphids like nobody's business.

Pictures of soybean aphids en masse -- or any swarming bugs -- give me the creepy crawlies, so I won't post a photo of them here.  But if you want to see what soybean aphids look like, take a look at Purdue University's page about them. Or just trust me when I say they're little yellow-green bugs and they generally cover the undersides of soybean leaves.

  • So, that's good, right?  Multicolored Asian lady beetles eat lots of soybean aphids, and that helps our soybeans grow, farmers are happy, we're happy.  Right?
  • Well, the multicolored Asian lady beetle does some other things too.  They migrate each year in the fall.  And before they migrate, they all get together to make their migration plans.  OK, I don't know if that's what they're doing, but they do combine to form great colonies of lady beetles.
  • They like to find tall sheltered places, like the where the wall of a house meets the roof, or the side of a mountain, or the sides of tall buildings.  They generally prefer light-colored buildings as places to hang out.

Again, I am not a fan of pictures of swarming bugs, but if you want to see what a whole bunch of multicolored Asian lady beetles congregating on the arm of a sofa looks like, be my guest.

  • The way they call to other multicolored Asian lady beetles is by releasing pheromones.  In most cases, you and I can't consciously smell pheromones.  But we can smell the pheromones of the multicolored Asian lady beetle.  And the pheromones smell terrible.  People describe it as "foul," "unpleasant," or "acrid." 
  • That might not be such a big deal, if there were only one multicolored Asian lady beetle on your arm.  But hordes of them swarming on the side of your house?  If you smashed them with a broom, those stinky pheromones (or perhaps it's another substance, one designed to ward off predators) would come out of the leg joints of the smashed lady beetles, and you'd have a pretty stinky mess.
  • And mess is right, because not only do the pheromones stink, they can also stain.  So if they're in your house and they're climbing up your aunt's beige silk curtains or they're crawling across your pearl-colored Asian carpet, perhaps thinking finally they're home, and you smash them, now you've got stinky lady beetle juice all over your aunt's lovely curtains and your pearl-and-now-lady-beetle-colored Asian carpet.

The stain of smashed Asian lady beetles.  All over your nice carpet. 
(Photo from University of Kentucky College of Agriculture, Food, and Environment)

  • So what, you say.  So they stink a little bit.  So they might make a stain if I smash them.  I just won't smash them.  I'll seal up the cracks and crevices of my house so they can't get in, they'll stay out side, I'll let them eat all my aphids, and we'll all be happy.
  • OK, well, they also bite.  The lady beetles native to the US do not bite.  But these foreign imports do.

This is the biting kind of ladybug (the multicolored Asian lady beetle).  You can identify it as such by the M or W shape on the lighter colored back of its neck behind the head.
(Photo from Maclean's in CA)

The multicolored Asian lady beetle can range in color from yellow to orange to russet, and the number of spots on their backs may vary.  But the one thing that is consistent is that M or W shape on the back of the neck.  You will also know it by its bite.
(Photo from Michigan State University)

  • Eh, big deal to that too, you say.  It's just a little bug.  The bite might sting a bit at first, but it's not like a mosquito bite, or a bee sting.  It's not going to itch and itch or really hurt or anything like that . . . right?
  • Um, sort of wrong.  It's true that the bite from a multicolored Asian lady beetle is more like an annoying pinch than anything especially painful.  But some people can have an allergic reaction.  And the way this allergy expresses itself is in the form of rhinoconjunctivitis, more commonly known as pink eye. 
  • If you've ever had pink eye, you know it's really unpleasant.  And people tend to back away from you like you have the plague.  If you watched Bob Costas covering the Olympics when he had pink eye, you know what I'm talking about.

Bob Costas, with pink eye.  He didn't get his from a reaction to a ladybug's bite, but let his painful-looking eyeballs be a cautionary tale to you nonetheless.
(Photo from Faboverfifty

  • Some sources also suggest that allergic reactions to the bite of a multicolored Asian lady beetle could trigger asthma.  And that is most certainly not fun.
  • Another problem is one which, in general, we hear about a lot when people talk about invasive species: lack of predators, and the inability of native species to compete.  In parts of southeast Michigan for example, the multicolored Asian lady beetle has so aggressively out-competed the native lady beetles for food, the native species are now severely threatened.
  • We're starting to learn enough about how ecosystems work to know that if even one plant or animal is threatened or on the verge of disappearing, that can have a huge ripple effect up the food chain.  So it's probable in another five or ten years or so, scientists will start telling us about some frog or bird or other creature that relies on the native ladybirds for food but can't find any to eat because there are only the noxious multicolored Asian lady beetles flying around, and so now the frog or bird or whatever it is has become at risk.

Here is an excellent drawing of the food chain involving a ladybug. The ladybug eats the aphid, the spider eats the ladybug, and the bird eats the spider.
(Drawing by Joshua Campes, posted at LALB)

  • Putting all this another way, the Asian ladybugs became an invasive species in this country -- and we were the ones responsible for the invasion.  You know, good intentions.  Trying to control a pest without using pesticide.  But unhappy results.
  • One final tidbit: the multicolored Asian lady beetle is cannibalistic.  That is, some of them eat their own larvae or their own eggs.  This seems to be an inherited trait, first of all.  But it also seems to be influenced by the number of aphids.  Lots of aphids, less cannibalism.  Few aphids, and they eat their young.  
  • I'm not saying we should bring in bags of some other aphid-eater from some other country to try to force the multicolored Asian lady beetle to eat their young. I'm just saying, something else to think about.  When you get a bite from a ladybug, did that ladybug use those same jaws to eat its own offspring?
  • Changes how you feel about ladybugs a little bit, doesn't it?

The ladybug. Cute classroom clipart, or vicious child-eating insect?
(Clip art from

Creature Control, Asian Lady Beetle
University of Minnesota Extension, Multicolored Asian lady beetles
Michigan State University Diagnostic Services, Multicolored Asian Ladybeetle
R L Koch, The multicolored Asian lady beetle, Harmonia axyridis: A review of its biology, uses in biological control, and non-target impacts J. Insect Sci., 2003, 3:32
Michael F. Potter et al., University of Kentucky, College of Agriculture, Food, and Environment, Asian Lady Beetle Infestation of Structures
Cornell University College of Agriculture and Life Sciences, Biological Control, Harmonia axyridis

No comments:

Post a Comment

If you're a spammer, there's no point posting a comment. It will automatically get filtered out or deleted. Comments from real people, however, are always very welcome!