Are Harlequin Bugs Harmful To Humans? What Damage Can They Do?

Harlequin bugs are bright and colorful insects often found near crop plants. They are renowned pests of cruciferous vegetables, but are harlequin bugs harmful to humans? Can you pick them up by hand and throw them away like aphids? Let’s discover more.

Harlequin bugs (Murgantia histrionica) not only have a rather interesting name, but their appearance makes them unique too. 

If you’ve spotted these bugs in your garden or suspect their presence, you might be wondering if it’s a cause for worry.

To answer your query quickly – yes, harlequin bugs are major pests and cause considerable damage to plants, especially vegetable crops. 

Let’s not beat around the bush and find out more about these bugs, what kind of damage they cause, and how to get rid of them.

Harlequin Stink Bug Nymphs

What Is A Harlequin Bug?

A common pest of cruciferous plants, harlequin bugs are native to North America. 

Note that these bugs aren’t to be confused with the harlequin ladybird. Despite the similarity in their names, they are two entirely different species of beetles.

So, harlequin bugs aren’t a ladybug species at all – they’re a kind of stink bug notorious for destroying vegetable crops. 

They are rather colorful, with varying patterns. 

Some look a lot like orange-tinted ladybugs with black spots, while others might look like black ladybugs or brown ladybugs. The nymphs may have stripe patterns instead.

Do Harlequin Bugs Bite Or Sting?

Before trying to touch or grab any insect, it’s always a good idea to check if it can hurt you. 

Harlequin bugs, for instance, possess piercing mandibles. These bugs are capable of both stinging and biting.

Thankfully, harlequin bugs usually aren’t aggressive and do not pose a serious threat to humans. 

You should still exercise caution while handling them and avoid direct contact with the skin, as they can inflict localized pain.

Are Harlequin Bugs Poisonous Or Venomous?

Insects of bright color are usually poisonous, with the colors acting as a warning sign to deter predators

Any toxic ladybug species, like larch ladybugs, would be a perfect example.

The harlequin bug, however, doesn’t have any poison. Instead, these bugs become extremely spicy due to the chemicals they consume from plants. 

This keeps them safe from birds, as birds typically avoid spicy food.

Are Harlequin Beetles Beneficial?

Harlequin beetles are disastrous insect pests and can cause extensive damage to vegetable plants. 

Piercing the plants in various places, they suck out the plant juices. The plants begin to wilt, turn brown, and eventually die.

So, Harlequin beetles aren’t exactly the kind of insect you’d consider beneficial. 

They are more of a garden and agricultural pest. 

However, they make it easier for gardeners to identify stressed plants, as those are the plants that usually get attacked by Harlequin bugs.

Harlequin Stink Bug Nymph

How Are Harlequin Bugs Harmful To Humans?  

These pests are particularly known to attack cabbage, which has also earned them the name harlequin cabbage bug. 

Other cruciferous plants like cauliflower, broccoli, kale, turnip, radish, etc., are at high risk around them too. 

If the usual preferences are unavailable, harlequin bugs turn to other crops like tomato, okra, squash, corn, and beans.

These bugs cause a great deal of damage and can destroy entire crops if left unchecked. 

They attack and feed on almost every part of a plant – the stems, leaves, fruits, and seeds alike. 

You may think of the kind of damage to be similar to that caused by Asian ladybugs, except it’s more severe for harlequin bugs.

How To Get Rid Of Harlequin Bugs?

Moving on, let us check out how you can rid your garden of these annoying and destructive pests. 

Depending on the stage of infestation and the relative effectiveness, you may try the following solutions.

Handpicking and vacuuming

If it’s just a small number of bugs, you can gently pick them off the plant by hand and throw them in a bucket of soapy water. 

Using warm water for this solution will make it even more effective.

Be careful not to squish harlequin beetles as they’re a kind of stink bug and can emit pungent odor as a defense mechanism. 

The other option is to take a vacuum cleaner and run it over the infested plants.

Parasitoid wasps

The use of natural predators is one of the best long-term pest-management techniques. 

Non-stinging parasitoid wasps are good at destroying Harlequin bug populations.

One can either buy the wasps online or plant companion plants that attract such natural enemies. 

You should note that the braconid wasps usually used in garden pest control don’t do much against these bugs.

Trap crops

Get a crop of cruciferous veggies early on before you grow the main batch of produce. 

The early trap crop will draw away most of the harlequin bugs and keep your main crop safe. 

You can dispose of the trap plant after harvesting the main crop.

Insecticidal soap

You can spray an insecticidal soap solution to effectively kill the bugs. The soap can penetrate their hard shells. 

However, it works as a direct-contact insecticide – you need to spray the solution directly on the adult harlequin bugs, nymphs, and eggs.

Harlequin Bug Nymph

Diatomaceous Earth

This reliable insecticidal agent works against a variety of pests, including Harlequin bugs. 

You can sprinkle diatomaceous earth over the bugs as well as apply it over the crops. 

It destroys the waxy coating on the bugs’ bodies and dehydrates them to death.

Should You Kill Them?

Unfortunately, you don’t have much of choice besides killing harlequin bugs that attack your plants. 

Unless you take the necessary steps to get rid of these bugs, they can cause extensive damage to your vegetable crops, fruits, and ornamental plants. 

Unlike the black and orange ladybugs that help gardeners by preying on harmful pests, the harlequin bug itself is a pest.

Frequently Asked Questions

What damage do harlequin bugs do?

Harlequin bugs are pests that cause serious damage to vegetable crops. They feed on various plants, including squash, cucumber, bean, and tomato plants. 
The harlequin bugs suck sap from the leaves of the plants, causing yellowing and wilting of the foliage. 
In some cases, the entire plant can be killed by this pest.

Are harlequin beetles beneficial?

Harlequin beetles are beneficial to their ecosystems because they feed on decaying wood, returning nutrients to the soil and encouraging new plant growth. 
They are also necessary as part of a food web, as they provide food sources for other animals such as birds, frogs, and lizards. 
Harlequin beetles also play an important role in controlling pest populations by preying on grubs and maggots.

Who eats harlequin bugs?

Harlequin beetles are a popular prey item for many different species of birds, reptiles, amphibians, and mammals. 
They are also eaten by some ants, spiders, and even their own larvae. 
The beetles provide a good source of nitrogen and other essential nutrients to these predators. 
Additionally, Harlequin beetle cocoons are eaten by shrews, frogs, lizards, and other small predators looking for an easy meal.

How do you fight harlequin bugs?

To fight harlequin bugs, it is important to keep your garden clean of leaf litter and debris because this is where the harlequin bug lays its eggs. 
If you find any in your garden, you should remove them by hand or use a powerful vacuum. 
You can also try spot-treating the garden with an insecticide containing acetamiprid or neem oil-based products. 
You can discourage insects from entering your garden by covering any bare soil with mulch or cotton balls soaked in water.
Another strategy is planting companion plants such as marigolds and carrots that are unappetizing to harlequin bugs.

Wrap Up

The harlequin bug isn’t uncommon in the United States, so it’s best to watch out for them and take the necessary pest control measures. 

Avoid leaving plant debris in your garden, especially from cruciferous plants. 

Thank you for reading, and I hope you can eliminate harlequin bugs in your garden before the infestation grows out of control.

Reader Emails

Over the years, our readers have shared us a few images of these bugs in their gardens or around their yards and in trails.

While harlequin bugs are not immediately harmful to humans, they are certainly damaging to crops.

Read a first-person account of what damage they can do to cruciferous plants in the letters from the reader’s section below.

Also go through some of the pics of these bugs in various stages of their lives to identify whether they are breeding in your garden.

Letter 1 – Harlequin Bugs

 

Can you identify beetle
I hope you can identify this insect, I think beetle, but not leaf beetle. The above photo shows it to be 3/8 inch. The below photos shows a pair (mating?). My location is San Luis Valley, Colorado. 8,000 ft elevation. Very arid. I first saw them at our creek on tumble mustard. A couple a days later they arrived in the garden 500 feet away on the horse radish leaves (probably 100). There are only a couple on the potatoes which are next to the horse radish. None on any other garden produce. Any ideas? Are they harmful or beneficial? What can discourage them? Thanks,
Dave

Hi Dave,
These are winged adult Harlequin Bugs, Murgantia histrionica. They do feed on mustard in vacant lots and fields. When they move to the garden they infest cabbage, kale, collards and related plants. The best control is to locate the eggs which are barrel shaped and in rows. Hand picking will also do the trick. Also, when your crop is harvested, immediately remove any remaining plants that serve to perpetuate the infestation.

Letter 2 – Harlequin Bugs

 

Beautiful bugs
Hello! It’s me again with pictures of some insects I found on my jogging trail, on a hill near home (Ensenada, México) They were on this plant. The bugs are a little bigger than 1/2 inch. I have not a clue. Arent they beautiful? Their name must be Leopard-something. I’m sending this to you because I love to take pictures and I think your site is great. So, don’t worry, I can live with my ignorance a few more months
Antonio Carbajal R.

Hi Antonio,
These are Harlequin Bugs, a type of Stink Bug in the family Pentatomidae.

Letter 3 – Seed Bug from Portugal

 

What kind of beetle is this?
Location: Lagoa Azul, Penha Longa, Sintra, Portugal
January 20, 2012 5:33 am
Hello ATB.
I ran into this beetle and have searched along almost all of your beetles in WTB but didn’t found it.
Maybe you could help me identify what kind of beetle this is. It seems some kind of Longhorn Beetle.
This was taken near a lake in Portugal. It is very common beetle in here. It was taken in the winter and this beetle has about 5cm long.
Can you please help me identify this beetle?
Thanks,
Signature: Diogo Ferreira

Harlequin Bug

Dear Diogo,
We hoped you enjoyed browsing through all of our beetles, the most numerous category on our website, but alas, you were searching the wrong category.  This is not a Beetle.  It is a True Bug.  We quickly identified it as
Lygaeus equestris and we found numerous photos on the FlickRiver page of the world’s best photos of Lygaeus equestrisIt can also be found on the Encyclopedia of Life website.  The genus Lygaeus belongs to the Seed Bug family Lygaeidae.

Dear Daniel,
Thank you very much. You were of great help.
I was indeed a little lost…
Thanks once again.
Diogo Ferreira.

Letter 4 – Harlequin Bug from Australia

 

Subject: Red and Black beetle in Melbourne Australia
Location: Melbourne Australia
January 17, 2013 10:28 pm
HI there
Just discovered your site, it is fascinating and I’ve ended up spending a few evenings looking at all these interesting bugs!
Haven’t quite found one that looks like these I found on my chilli plant the other day.I have never seen these before and have had my chilli plant for about 4 years. When I first noticed them they were all congregated on one chilli which was drying up- not sure if they were the cause of that though.Someone suggested they perhaps were attracted to it as it was the same colour as them and were having a bit of a party on it. What fascinated me was there seemed to be two quite distinct looks to the beetle- one was much smaller and rounder and almost looked like a lady bug-but there were only 2 of them like that compared to about 10 of the others.(unfortunately that photo of the smaller one is a bit blurry sorry).Are they the female ones or baby ones perhaps?
Have also noticed that they go into hiding somewhere when our temperatures get too hot eg yesterday when we hit 40 deg C, but they come out all over my chilli plant when the weather is a little cooler ( still summer here though)
Initially thought they may be blister beetles ( but the antannae look a little different to photos I saw?)and am worried they are around as have a little toddler who is curious about everything including bugs. So would appreciate your help in identifying these so that I know whether to try to get rid of them ( how?)or let them be!
Signature: Melbournegal

Harlequin Bug

Dear Melbournegal,
Our initial impulse, which proved correct, was that this is a Red Bug in the family Pyrrhocoridae.  Upon researching that suspicion, we found a matching image on FlickR that was identified as a Harlequin Bug or Fire Bug, probably
Dindymus ventralis.  The common name Harlequin Bug is used for at least one other insect, a species of Stink Bug found in North America.  Firebug is a common name used for a European member of the family Pyrrhocoridae.  Your individuals are both immature nymphs.  Adults have fully developed wings.  The presence of nymphs in your garden is an indication that there is breeding activity going on.  When we searched the genus name provided by FlickR, we found a blog called A Year in a Gippsland Garden with an excellent first person encounter with the Australian Harlequin Bugs, here called Dindymus versicolour.  The site provides this information:  “For anyone looking at these little bugs in the garden and wondering if they are a potential problem or not the answer is a resounding ‘Yes!’  The Harlequin bug does not take great big obvious bites out of anything, it hides and sucks the life out tender stems (and fruit). Look for stem damage and wilting flower buds and fruit. In my garden I have observed them in greatest numbers on Callistemon, Australian native hibiscus, nasturtium, tomatoes, and hollyhocks. They have also been in numbers on sweetcorn, sunflowers, sage and roses.
These are one of the few bugs to actively hide from potential predators. If you watch them carefully you will notice that when they are not feeding they will stay in sheltered positions.  If they are caught out in the open they will dive behind leaves and stems as you approach. They don’t go far and sneak back out when you stop moving.  One or two bugs on their own won’t do much harm, but the sad reality is that this is often not a bug that comes in ones or twos. Not for long if you plant a tasty crop anyway. In numbers they can overwhelm tender plants, particularly nice juicy ones having a growth spurt.”  The PaDil Biosecurity Website has some information and photos.
  Your dried chili is a sign that these Harlequin Bugs are feeding.  We don’t normally provide extermination advice.  This is a native species for you that has adapted to feeding on cultivated plants.  We would recommend hand picking to control them.

Immature Harlequin Bug

Wow that was a fast response- thanks so much for the ID. Good that they aren’t harmful to my little toddler, but a pity they are sucking the life out of my chilli plant…. Don’t really enjoy getting rid of bugs but looks like I might have to if I want to keep that lovely chilli plant…
Thanks again for spending the time to find this out for me, you’re fantastic!
Melbournegal
(Bianca)

13 thoughts on “Are Harlequin Bugs Harmful To Humans? What Damage Can They Do?”

  1. I am pretty sure this is actually the adult version of Spilostethus pandurus which is also seen in Cyprus but I have definitely seen a few in Portugal. I say this based on the brown wings that do not have a white ring, and the shoulders which have a continuous black marking all the way up to the head. The triangle at the top of the wings too is more narrow and sharper. Of course it would be better with the head in the photo but I believe it would only confirm it.

    http://www.whatsthatbug.com/2014/04/25/firebug-nymph-cyprus/

    Someday I’ll send in my pictures of Spilostethus pandurus as both adult and juvenile (don’t want to overwhelm you in the busy season — unless you signal otherwise as it is prime season for them now). They actually seem to have quite a lot of personality but tend to be lone bugs (perhaps because they can fly) rather than aggregate like the much smaller non-flying Fire bugs.

    Oh, ha ha… perhaps you might consider putting in a section on Insect movies & docs. Seems there is one with a section on the perils of being a Japanese Red Bug Mama (Animal Planet & BBC), and one on the Japanese love affair with bugs just to get you started:

    http://www.bbcamerica.com/earth-night/guide/life/insects/

    http://www.post-gazette.com/ae/movie-reviews/2010/08/19/Beetle-Queen-documentary-explores-Japan-s-love-affair-with-insects/stories/201008190361

    http://www.pbs.org/independentlens/beetle-queen-conquers-tokyo/

    And of course there are also all the Bee movies such as Queen of the Sun. :^)

    Reply
    • Hi Curious Girl,
      We would love your images of Spilostethus pandurus and if you send them today or tomorrow, we may be able to post them prior to leaving town for a few weeks. Please use the scientific name as the subject line to catch our attention as our identification requests are increasing as you surmised.

      Reply
  2. I am pretty sure this is actually the adult version of Spilostethus pandurus which is also seen in Cyprus but I have definitely seen a few in Portugal. I say this based on the brown wings that do not have a white ring, and the shoulders which have a continuous black marking all the way up to the head. The triangle at the top of the wings too is more narrow and sharper. Of course it would be better with the head in the photo but I believe it would only confirm it.

    http://www.whatsthatbug.com/2014/04/25/firebug-nymph-cyprus/

    Someday I’ll send in my pictures of Spilostethus pandurus as both adult and juvenile (don’t want to overwhelm you in the busy season — unless you signal otherwise as it is prime season for them now). They actually seem to have quite a lot of personality but tend to be lone bugs (perhaps because they can fly) rather than aggregate like the much smaller non-flying Fire bugs.

    Oh, ha ha… perhaps you might consider putting in a section on Insect movies & docs. Seems there is one with a section on the perils of being a Japanese Red Bug Mama (Animal Planet & BBC), and one on the Japanese love affair with bugs just to get you started:

    http://www.bbcamerica.com/earth-night/guide/life/insects/

    http://www.post-gazette.com/ae/movie-reviews/2010/08/19/Beetle-Queen-documentary-explores-Japan-s-love-affair-with-insects/stories/201008190361

    http://www.pbs.org/independentlens/beetle-queen-conquers-tokyo/

    And of course there are also all the Bee movies such as Queen of the Sun. :^)

    Reply
  3. I would like to know how Harlequin Bugs get about, do they fly? We have thousands here, we have to spray them or we would have NO fruit as where they suck goes bad and destroys the fruit, namely our nectarines & now they have migrated to the apples. So we are trying to work out a plan so thats why we want to know if they fly?

    Reply
  4. I’ve searched everywhere for advice on eradication. Australian sites all recommend handpicking.
    Handpicking is not an option however, (as anyone in an affected zone knows) This is because they breed rapidly in plague numbers and for every ten you pick, a thousand more hatch. Advising handpicking to control these bugs is like telling farmers to handpick in a locust plague.
    US sites recommend chemical eradication however the products identified in the US are not available here.
    Finally I strongly doubt these things are natives. I’ve never seen one on a native bush.

    Reply
    • We had never seen them before moving to the Mornington Peninsula. They are a plague! Killing everything…. herbs, beans, peas, strawberries, all berries, nasturtiums, salvias, fennel, potato shoots & flowers, passionfruit… we even found them decimating corn tassles, then our corn wasn’t fertilised properly!
      So far we have found only 3 ways to kill them.
      Splat them. Fry them with a cooks torch.
      Put boiling water into a bucket and shake them off the plants into the bucket.
      Still millions around and we do these things morning and arvo.
      They are shocking.
      We even vac up leaves around the paving and yard. They even eat their dead!
      Worst pest ever.

      Reply
  5. I’ve searched everywhere for advice on eradication. Australian sites all recommend handpicking.
    Handpicking is not an option however, (as anyone in an affected zone knows) This is because they breed rapidly in plague numbers and for every ten you pick, a thousand more hatch. Advising handpicking to control these bugs is like telling farmers to handpick in a locust plague.
    US sites recommend chemical eradication however the products identified in the US are not available here.
    Finally I strongly doubt these things are natives. I’ve never seen one on a native bush.

    Reply
    • We had never seen them before moving to the Mornington Peninsula. They are a plague! Killing everything…. herbs, beans, peas, strawberries, all berries, nasturtiums, salvias, fennel, potato shoots & flowers, passionfruit… we even found them decimating corn tassles, then our corn wasn’t fertilised properly!
      So far we have found only 3 ways to kill them.
      Splat them. Fry them with a cooks torch.
      Put boiling water into a bucket and shake them off the plants into the bucket.
      Still millions around and we do these things morning and arvo.
      They are shocking.
      We even vac up leaves around the paving and yard. They even eat their dead!
      Worst pest ever.

      Reply
  6. put cheap dishwashing liquid into a spray bottle (double what you would use to do dishes) spray the bugs and it clogs up their gills and they die in a few seconds, I always have a couple of old spray bottles in the garden from spring at the ready

    Reply

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