Cotton Harlequin Bug: Essential Facts and Tips

Cotton crops face numerous challenges involving pests, one of which is the cotton harlequin bug. This colorful and destructive insect thrives on vegetation, causing damage to various plants, particularly those from the Brassicaceae family, such as broccoli, cauliflower, cabbage, and kale 1. Other plants that may be targeted by harlequin bugs include mustards, radish, and even some fruit and vegetable crops like beans, tomatoes, and onions 2.

These shield-shaped or oval bugs suck the fluids from plant tissues, leaving small white spots on the leaves, and eventually, affecting the overall health of the plant 3. Being aware of the presence and impact of cotton harlequin bugs in your garden or farm is crucial for timely and effective pest management.

Cotton Harlequin Bug Overview

Appearance and Identification

The Cotton Harlequin Bug (Tectocoris diophthalmus) is a vibrant jewel bug, known for its striking colors. Some key features include:

  • A mix of red, orange, blue, black, and metallic green shades
  • Oval-shaped body
  • Distinctive markings

These bugs are typically found on the so-called cotton plant, but their bright colors make them easily recognizable.

Distribution and Habitat

The Cotton Harlequin Bug can be found in various regions, such as:

  • Eastern Australia
  • New Guinea
  • Pacific Islands

These bugs prefer a habitat that includes cotton plants, although they can be found on other host plants in their native range.

In conclusion, the Cotton Harlequin Bug is a unique and visually striking insect with a diverse habitat spanning multiple regions. Its captivating appearance makes it easily identifiable and an interesting subject for study.

Life Cycle and Behavior

Eggs

The life cycle of cotton harlequin bugs begins with their egg stage. Female bugs lay clusters of drum-shaped eggs on leaves. These eggs have circular “lids” which show their unique appearance.

Nymphs

Harlequin bug nymphs undergo a process called incomplete metamorphosis. They go through five instars as they develop.

  • First instar nymphs are small and reddish-orange.
  • Nymphs become larger and darker in color with each molt.

Adults

Males and females show some differences in appearance:

  • Males: Brighter colors and smaller in size
  • Females: Duller colors and larger in size

Adult harlequin bugs feed on plant sap, which can cause damage to crops such as cruciferous vegetables.

Comparison of Nymphs and Adults:

Feature Nymphs Adults
Size Smaller Larger
Color Reddish-orange (Instars vary) Brighter in males, duller in females
Metamorphosis Incomplete (Five instars) Not applicable

As cotton harlequin bugs move through their life cycle:

  • Eggs hatch into nymphs
  • Nymphs go through five instars
  • They reach full adulthood and can reproduce

Host Plants and Feeding Damage

Impact on Agricultural Crops

Harlequin bugs, or Murgantia histrionica, primarily affect plants in the Brassicaceae family, which includes vegetables such as:

  • Cabbage
  • Broccoli
  • Cauliflower
  • Mustard
  • Radish

These pests are also known to cause damage to other crops like:

  • Beans
  • Greens
  • Tomatoes

Feeding on the sap of these plants, they may cause wilting, browning, and eventual death1. Their presence can be particularly detrimental in the southern United States due to favorable conditions for their population growth2.

Effects on Ornamental Plants and Gardens

In addition to agricultural crops, harlequin bugs can have a negative impact on ornamental plants and gardens, including the Malvaceae family, which is home to plants such as:

  • Cotton
  • Hibiscus
  • Illawarra flame tree3

Harlequin bugs usually feed on stems, young shoots, and flower buds, which can lead to:

  • Stunted growth
  • Deformed flowers
  • Reduced seed production

In cotton plants specifically, they may cause cotton bolls to drop prematurely, leading to reduced yield4.

Crop / Plant Family Impact / Damage
Brassicaceae (veggies) Wilting, browning, death, reduced fruit/vegetable production1
Malvaceae Stunted growth, deformed flowers, reduced seed production, boll drop3 4

Overall, cotton harlequin bugs can cause significant damage to both agricultural crops and ornamental plants. Effectively managing these garden pests can help mitigate their effects and protect the health of your crops and garden.

Pest Management Strategies

Cultural Control Methods

Cultural control methods help prevent and reduce harlequin bug infestations. These methods include:

  • Crop rotation: Changing crops from season to season disrupts the harlequin bug life cycle.
  • Clean up: Removing crop residues and organic debris prevents bugs from hiding and reproducing.
  • Trap crops: Yellow mustard or horseradish attract harlequin bugs, drawing them away from the main crop.

Biological Control Agents

Several natural predators and parasites help control harlequin bugs. Examples include:

  • Predatory insects: Lady beetles, lacewings, and predaceous stink bugs prey on harlequin bugs.
  • Parasitic wasps: These insects lay eggs inside harlequin bug eggs, killing them.

Chemical Control Options

Several chemical options combat harlequin bug infestations:

  • Insecticidal soap: A soapy water solution helps control small infestations.
  • Pyrethrin: A natural insecticide derived from chrysanthemum flowers. Use as directed on the label.

Comparison table:

Method Pros Cons
Cultural control Non-toxic, easy to implement, sustainable Limited effectiveness in large farms
Biological agents Natural, minimal harm to beneficial insects & environment Can be slow to control infestations
Chemical control Quick results, effective against larger infestations May harm non-target organisms

Remember that proper management involves monitoring, timely action, and selecting appropriate strategies. Consult your local extension office for tailored advice on managing harlequin bugs in your region.

Relationship to Other Bugs

Comparison to Stink Bugs

Cotton harlequin bugs, or Murgantia histrionica, belong to the Hemiptera order, which also includes stink bugs and leaf-footed bugs1. These true bugs share some common traits:

  • Both have piercing-sucking mouthparts used for feeding on plant sap
  • They often emit unpleasant odors when disturbed or crushed
  • Their bodies are generally shield-shaped or oval

However, there are noticeable differences between them:

Feature Harlequin Bug Stink Bug
Size 1/4 to 3/8 inch long2 Up to 3/4 inch long
Color and markings Robust and black, with vivid red, orange, or yellow markings2 Generally brown or green, with fewer markings
Preferred host plants Vegetables in the Brassicaceae family3 Various crops, fruits, and ornamental plants

Notable Similar Species

The hibiscus harlequin bug is a close relative of the cotton harlequin bug. Both insects share similar characteristics:

  • Shield-shaped or oval bodies
  • Distinct, vibrant colorations
  • Found mainly on plants within specific plant families

However, the hibiscus harlequin bug is specific to certain hibiscus species and other members of the Malvaceae family, whereas the cotton harlequin bug attacks vegetables in the Brassicaceae family3.

In summary, while cotton harlequin bugs share similarities with stink bugs and other Hemiptera species, they have unique characteristics that set them apart.

Footnotes

  1. Texas A&M University 2 3

  2. University of Florida Entomology 2 3

  3. University of Maryland Extension 2 3 4

  4. New Mexico State University 2

Reader Emails

Over the years, our website, whatsthatbug.com has received hundreds of letters and some interesting images asking us about these insects. Scroll down to have a look at some of them.

Letter 1 – Cotton Harlequin Bug from Australia

 

Pretty Little Beetle
Location: New South Wales, Australia
April 11, 2011 10:50 pm
We passed this on our way to Bondi Beach in Australia. It was just a few blocks from the beach. It seemed to be dead. It didn’t move. It was raining that day so I didn’t have my good camera. The colors were much brighter than the photo.
Signature: Thanks! Heather

Cotton Harlequin Bug

Hi Heather,
This is a Cotton Harlequin Bug,
Tectocoris diophthalmus, a relatively common Jewel Bug in the family Scutelleridae.  It is not a beetle.  You may visit the Brisbane Insect Website for additional images of this lovely little creature.

Letter 2 – Cotton Harlequin Bug Nymphs from Australia

 

What’s my Australian bug please?
Location: Queensland
October 31, 2010 2:42 pm
I thought at first that they were really large lady bugs but they look a little more robust that that. Found on a hibiscus leaf in Queensland, Australia
Signature: Australian bugs are just bigger

Cotton Harlequin Bug Nymphs

You have submitted a photograph of Cotton Harlequin Bug Nymphs, Tectocoris diophthalmus, and you can find matching images on the Brisbane Insect Website.  They feed on hibiscus and related plants.

Letter 3 – Cotton Harlequin Bug from Australia

 

What’s that bug?
I was just websurfing with a ‘cool site finder’ when I found that one. I never thought of searching a website to identify a bug before… And I think it’s pretty cool. I would be glad if you could help me identify this insect, which I found not too far from my home. Please see the attached files.
Bye,
Stephane

Hi Stephane,
We knew this was exotic for us here in southen California, but your letter gave us no hint as to where your home is. Luckily, the pod caused us to search Australian insect sites and we located your Cotton Harlequin Bug, Tectocoris diophthalmus. They are also called Hibiscus Harlequin Bugs. The patterns vary between individuals. You other photo shows a cluster of nymphs.

Letter 4 – Cotton Harlequin Bug from Australia

 

what is this bright bug in Australia?
I found this amazingly colorful bug on our concrete roof in Bondi (Sydney) Australia about 3 stories up. It is roughly 3⁄4” long and has very bright colors as you can see in the photo. It was alive and moving the antenna you can see coming out of what I think is the head. Can you help me out? (It was lightly raining the day we found him. Hence the water drops on his back). Just to follow up, I think this might be a cotton harlequin bug or a hibiscus harlequin bug. I found some pictures of those online. Does that seem like a reasonable guess?
Cheers!
Amy

Hi Amy,
You are absolutely correct, a Cotton Harlequin Bug, AKA a Hibiscus Harlequin Bug.

Letter 5 – Cotton Harlequin Bug from Australia

 

Strange Australian beetle.
You’ve helped me identify a wasp before, and I’ve got another mystery for you. Your beetles pages don’t include anything on this beautiful orange creature. I found it in Brisbane, and there was no shortage of them on these strange black seed pods. I counted about 30 in a single tree. They’re quite responsive, and will actively run away from a camera or hand, but rarely try to fly. Their elytra don’t open – the wings slide out from the side. They have a long proboscis which, I assume, they use for sucking food out of the seed pods. They’re about 2cm long, and about 1.5cm across.
Lawrence.

Hi Lawrence,
The Cotton Harlequin Bug, Tectocoris diophthalmus is also called Hibiscus Harlequin Bug. You didn’t find it on our beetle pages because it is located on the True Bugs pages. The sucking mouthparts are a dead giveaway for Hemipterans, or True Bugs as opposed to the chewing mouthparts of beetles. Your photos are beautiful and show the color variations within the species.

Letter 6 – Cotton Harlequin Bug

 

seen near Forster.
Hi there,
We’re overseas people from The Netherlands. We took a photo from a beetle on the seeds of trees close near the water in Forster, NSW. There were hundreds of them. Can you tell me the name of this beetle. Thanks,
regards,
Kees Rullens

Hi Kees,
This is not a beetle, but a True Bug. It is a Cotton Harlequin BugTectocoris diophthalmus, also called the Hibiscus Harlequin Bug.
.

Letter 7 – Cotton Harlequin Bug from Australia

 

Strange orange bug with shiny symmetrical green patches
December 28, 2009
I was standing outside the pharmacy building at the Sydney University, on an Australian Spring afternoon, when this orange bug/beetle landed on my arm. I’m not sure if the bug fell out of a tree (many Eucalyptus trees around) or flew and landed on me, but it didn’t seem to fly away when i flicked it off. It just fell onto the concrete and kind of crawled slowly away. It was slow enough for me to take a couple of good close up pictures of it, including a nice mug shot. To date, I still haven’t been able to identify it, so I was wondering if you could help me out a little. Thanks =)
Mr Tan Luu
Sydney University, NSW, Australia

Cotton Harlequin Bug
Cotton Harlequin Bug

Dear Mr. Luu,
This shimmery creature is a Cotton Harlequin Bug, Tectocoris diophthalmus.  It is also called a Hibiscus Harlequin Bug and you can see photos of it on the Brisbane Insect Website.

Letter 8 – Cotton Harlequin Bug

 

What is this bug?
Location: Sydney, Australia
March 24, 2011 8:06 pm
Hi, I found this bug in the grass near Hyde Park in Sydney in 2003. Can you please tell me what it is?
Signature: Carey

Cotton Harlequin Bug

Hi Carey,
This little beauty is an immature Cotton Harlequin Bug,
Tectocoris diophthalmus, one of the Jewel Bugs in the family Scutelleridae.  You may read about it as see images of the adult insect on the Brisbane Insect Website.

Hi Daniel,
Thank you so much for the fast response! I’ve been wondering about this for years and it’s great to finally know.
Thanks again,
Carey

Letter 9 – Cotton Harlequin Bug from Australia

 

Subject: I can’t find this one anywhere please help
Location: I think Australia
May 4, 2014 4:34 pm
Hey bugman buddy, I was wondering if you could help me identify this colorful bug. Thanks for all your help I will try to also make a donation soon. Thanks again
Signature: Brandon

Cotton Harlequin Bug
Cotton Harlequin Bug

Hi Brandon,
We didn’t notice until we were actually creating a posting that this photo was taken in “I think Australia” which leads us to think you did not take the image.  Please clarify where the image came from if you did not take it as our submission clearly states:  “Also, you swear that you either took the photo(s) yourself or have explicit permission from the photographer or copyright holder to use the image.”  This is a Cotton Harlequin Bug,
Tectocoris diophthalmus, and it is indeed from Australia.  You can read more about it on the Brisbane Insect website.

Authors

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  • Bugman

    Bugman aka Daniel Marlos has been identifying bugs since 1999. whatsthatbug.com is his passion project and it has helped millions of readers identify the bug that has been bugging them for over two decades. You can reach out to him through our Contact Page.

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  • Piyushi Dhir

    Piyushi is a nature lover, blogger and traveler at heart. She lives in beautiful Canada with her family. Piyushi is an animal lover and loves to write about all creatures.

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6 thoughts on “Cotton Harlequin Bug: Essential Facts and Tips”

  1. We have these in our kindy, they hang around 1 particular tree & seem to eat out of the large seed pods, (not sure what the tree is called), have been looking for a name for them as the children call them stink bugs, & i know their not. Everywhere i have found on the net so far that has these bugs is down south but we are in queensland, just thought i would share with you!

    Reply
  2. I got mine yesterday from my garden in Timor Leste. Just love dit and thought it was amazing. So I wanted to know who I had got. And I came here to your website.

    Reply

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