Bordered Plant Bug: All You Need to Know for Healthy Gardens

The Bordered Plant Bug is a fascinating insect commonly found in gardens across North America.

With its striking deep gray-blue body and orange trim outline, this bug is easily distinguishable from other true bugs.

As they grow, they can reach up to half an inch in length, making them relatively easy to spot in the wild.

While the adult Bordered Plant Bug features a dark black, semi-diamond-shaped “tail end,” their nymphs showcase a metallic blue/black color with an orange warning triangle at the center.

These nymphs can sometimes be challenging to identify, as they don’t look much like their adult counterparts.

Bordered Plant Bug Overview

Classification

The Bordered Plant Bug belongs to the Largidae family, which is part of the Hemiptera order, also known as true bugs.

Within this family, there are multiple species and genera, including the Larginae subfamily and the Pyrrhocoroidea superfamily.

Identification

1. Size: Adult Bordered Plant Bugs typically measure up to 1/2 inch (12.7 mm) in length.
2. Coloration:
   • Body: The primary body color of the Bordered Plant Bug is a deep gray-blue.
   • Trim: One of the most distinguishing features of this bug is its vibrant orange trim outline, which borders its body.
3. Tail End: The Bordered Plant Bug features a unique dark black, semi-diamond-shaped structure at its tail end.
4. Nymphs: They exhibit a metallic blue/black hue and have a notable orange warning triangle at their center. Unlike adults, nymphs lack fully developed wings.
5. Wings: Adult Bordered Plant Bugs have well-developed wings that cover their body. These wings often showcase the deep gray-blue coloration and are bordered by the distinctive orange trim.

Some related species, such as the Jadera antica, can be distinguished by their distinct differences in coloration, which is brownish-salmon color, with fuscous dots on upper surface and thorax

Comparing these two species in a table format:

Species	Coloration	Markings
Bordered Plant Bug	Deep gray-blue body with orange outline	Semi-diamond shaped dark black tail end
Jadera antica	Brownish-salmon	Fuscous dots on upper surface and thorax

This information should help you better identify and understand the Bordered Plant Bug’s physical characteristics.

Habitat and Range

Life Cycle and Reproduction

The bordered plant bug has a distinct life cycle that includes nymphs, which grow and develop throughout the summer months.

The nymphs are metallic blue/black in color and have an orange, warning triangle at their center¹. Some key characteristics of nymphs include:

• Lack of fully developed wings
• Smaller size compared to adults
• Dramatic color changes as they mature

Eggs and Overwintering

Bordered plant bug adults lay their eggs during the summer, which are then left to overwinter.

This allows the eggs to survive through the cold winter months and hatch once the temperatures rise again.

The life cycle and reproduction of the bugs are intrinsically linked to the seasonal changes in their environment.

Feeding and Habits

Common Plants and Trees

Here are some of their preferred food sources:

1. Seeds and Shoots: They primarily feed on the seeds and shoots of hardwood trees. This feeding habit can sometimes lead to minor damages to the plants, but they are generally not considered significant pests.
2. Weeds: Various types of weeds serve as food sources for these bugs. They extract nutrients from these plants, helping in indirectly controlling the weed population in some areas.
3. Garden Plants: In gardens, they are known to feed on a variety of plants. Some of their favorites include ornamental grasses, roses, chrysanthemums, and other flowering plants.
4. Fruits and Vegetables: Bordered Plant Bugs can sometimes be found on fruit plants like strawberries and blueberries. They might also be attracted to vegetable plants, although they are not primary pests for these crops.
5. Other Sources: Apart from plants, these bugs have been observed scavenging on animal feces and dead insects, indicating a varied diet.

Some examples of plants and trees these bugs feed on include:

• Ornamental grasses
• Roses
• Chrysanthemums
• Clover
• Strawberries
• Blueberries
• Tomatoes

These insects can also be found on herbs and other garden plants.

Piercing-Sucking Mouthparts

Bordered Plant Bugs, like other true bugs, have piercing-sucking mouthparts that they use to feed on plant parts, particularly seeds.

They pierce the plant stems and suck out the plant juices, which can sometimes result in damage to the plant.

However, the damage is typically minimal.

To better understand the feeding habits of Bordered Plant Bugs, let’s compare them to Spittlebugs, another common garden insect:

Bordered Plant Bug	Spittlebug
Feed on a variety of plants and trees	Feed on plants like grasses, roses, chrysanthemums, clover, strawberries, herbs, and other garden plants
Use piercing-sucking mouthparts for feeding	Pierce plant stems and suck plant juices
Damage to plants is usually minimal	Damage to plants may vary, depending on the infestation

Remember to keep an eye out for these insects in your garden and take necessary measures when needed.

Bordered Plant Bugs in Gardens

Effects on Garden Plants

The Bordered Plant Bug (Largus cinctus) is often found in gardens, where it feeds on various plants.

Although they can cause damage to garden plants by feeding on leaves and fruits, they are usually not harmful enough to warrant drastic control measures.

Natural and Chemical Control

To control Bordered Plant Bugs in gardens, some natural and chemical control methods can be used.

Natural control methods:

• Introduce beneficial insects like ladybugs and lacewings that prey on the nymphs of Bordered Plant Bugs
• Handpick the bugs from your plants and dispose of them

Chemical control methods:

• Use insecticidal soap or horticultural oil to control the population; however, this may also harm beneficial insects in your garden.

Pros and Cons of control methods:

Method	Pros	Cons
Natural control	Eco-friendly, cost-effective	May not be completely effective
Chemical control	Quick results	Can harm beneficial insects, potential environmental impact

At-Home Management Techniques

Mason Jar Method

The Mason Jar Method is a simple, non-toxic approach to managing Bordered Plant Bugs. Here’s how you can do it:

• Fill a mason jar halfway with a mixture of water and dish soap
• Trap the bug between the jar and the surface it is on
• Allow the bug to fall into the soapy water
• Dispose of the dead bug and replace the water when necessary

This method is beneficial because it’s:

• Eco-friendly
• Cost-effective
• Easy to implement

However, it might not be the best solution if you’re dealing with a large infestation.

Shop Vac Method

Another option for managing Bordered Plant Bugs is the Shop Vac Method. Follow these steps:

1. Purchase a shop vac with a fine mesh filter
2. Vacuum the bugs off your plants and surrounding areas
3. Empty the vacuum outside, away from your garden

Pros	Cons
Effectively removes bugs	Requires a shop vac
Can handle bigger infestations	Must empty vacuum regularly

Keep in mind:

• The Shop Vac Method works best for larger infestations
• Regular vacuuming helps prevent future problems

In summary, the Mason Jar Method is ideal for eco-friendly, small-scale management, while the Shop Vac Method is better for larger infestations.

Choose the technique that best suits your situation and enjoy a bug-free garden!

Conclusion

The Bordered Plant Bug, a member of the Largus species, is a captivating insect native to North America, with some presence in Central and South America.

Distinguished by its deep gray-blue body and vibrant orange trim, it stands out in gardens and wild areas alike. While often mistaken for other bugs, its unique appearance and feeding habits set it apart.

Predominantly found in wild areas, gardens, and some urban spaces, this bug has a penchant for feeding on a variety of plants, from hardwood tree shoots to garden flowers.

Although they can sometimes be seen as nuisances, their role in controlling weed populations and their minimal impact on garden plants make them a relatively benign presence.

By understanding their geographical spread, preferred habitats, and feeding preferences, we can better appreciate the Bordered Plant Bug’s role in our ecosystem and coexist harmoniously with this intriguing insect.

Footnotes

1. UC Master Gardeners – Diggin’ it in SLO – ANR Blogs ↩ ↩² ↩³
2. Entomology and Nematology Department ↩ ↩²

Reader Emails

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

Letter 1 – Bordered Plant Bug

Plant bug ID
Location: Hyampom, CA
May 25, 2011 1:25 am
Hello,
I am trying to ID this little guy. It was found in Northern California near the Oregon border. It hasn’t caused any plant damage that I can see.
It resembles a Boxelder bug but has no x marking on its back. Everything else seems the same (color, shape and size).
Do you have any idea what it might be?
Thanks in advance.
Signature: Steve

Hi Steve,
Your mistaking this individual for a Boxelder Bug is understandable.  It is a Bordered Plant Bug, most likely Largus californicus.

According to BugGuide, it feeds upon:  “Mostly plants (flowers, leaves, fruit) from a range of families, with a preference for Lupines. L. californicus is not considered a “pest species” of economic importance.” 

We will be going through our archive to find some nice high resolution images of this Bordered Plant Bug to use in our presentation at the Theodore Payne Foundation this Saturday.

Letter 2 – Bordered Plant Bug from Mexico

Subject: What is this bug
Location: Guadalajara Mexico
August 22, 2013 1:52 pm
I live in Guadalajara Mexico and there are these bugs everywhere. I have been here for three years now and this is the first year that I have seen them.
Signature: Jeffeory

Dear Jeffeory,
We have seen photos of this True Bug in the past, and we believe we even have an example in our archives, however, we are not currently able to identify it.  Perhaps one of our readers will have better luck and provide us with an identification.

Identification Courtesy of Karl
Hi Daniel and Jeffeory:
I see that a few comments have already been submitted regarding this bug but I think I will weigh in as well with some additional information. I came across large numbers of these nymphs earlier this year while on a hike near Chirripo National Park in Costa Rica.

To be clearer, they looked pretty much exactly like the one in Jeffeory’s photo. Unfortunately, there were no adults associated with them so identification was quite challenging. I finally decided that they were Bordered Plant Bugs (Largidae) in the genus Stenomacra, possibly S. marginella, which ranges from the southern USA to at least as far south as Costa Rica.

However, there are several other Stenomacra species in the region and I was not able track down enough descriptive information for the nymphs of these species to conclusively eliminate them as candidates. This particular black and orange color scheme appears to be common for Stenomacra species as well as some Largus species.

Actually, Largus marginella is a junior synonym for Stenomacra marginella. So Cesar and Zee were probably both close to the mark with the comments they provided. I would go with Stenomacra sp. based on body form and overall appearance. Regards.  Karl

Letter 3 – Mating Bordered Plant Bugs

Please identify this bug
Location:  Phoenix Arizona
August 7, 2010 8:32 pm
Hi,
It is summer here in Phoenix AZ and I have these guys all over my front yard which is mostly stone.
I’ve lived in Phoenix for a long time and never had my yard over ran like this.
Thanks,

You have mating Bordered Plant Bugs in the genus Largus, most likely Largus californicus.

Letter 4 – Bordered Plant Bug

Please identify
Hello Bugman,
Here’s a better set of pictures of a bug I’d like to have identified, please. These guys are everywhere and on every plant in our back yard in the Houston area. Every year there seem to be more of them than the year before.Have a wonderful day!
Beatrix Spires

Hi Beatrix,
Thanks for the clear image. This is a Bordered Plant Bug, Largus succinctus. They form aggregations like other Hemipterans, of which the Boxelder Bugs are the most notorious.

Letter 5 – Bordered Plant Bug

What’s this bug?
This beetle, found in the Sacramento area of California, appears diurnal, and heat tolerant. Most plentiful in May & June. What am I looking at?
Doc

Hi Doc,
This isn’t a beetle. It is a true bug, one of the Bordered Plant Bugs, Largus californicus. You can see matching images on BugGuide.

Letter 6 – Bordered Plant Bug

one of MANY bugs in my yard
April 25, 2010
Hi and thanks for providing such an informative website! I live on acreage (digger pines and oaks) in the Sierra foothills and have noticed a BUNCH of these bugs milling about. What the heck are they?

I am allergic to the Western Bloodsucking Conenose but don’t think that this one bites. Well, at least it hasn’t bit me yet. I noticed these guys in the spring-like weather. Any information is much appreciated.

ALSO, just so you know, the dent on this bug’s back was not caused by my hand (or foot) – don’t know how it received it’s injury but that hasn’t impeded it’s ability to get around at all. Thanks again!
Pam
Penn Valley, CA

Hi Pam,
Your bug is a Bordered Plant Bug in the family Largidae and the genus Largus, and it is most likely Largus californicus. 

According to BugGuide it feeds upon: “Mostly plants (flowers, leaves, fruit) from a range of families, with a preference for Lupines. L. californicus is not considered a ‘pest species’ of economic importance.”

Letter 7 – Bordered Plant Bug in Griffith Park

Subject: tan bettle with yellow edges
Location: Griffith Park, Los Angeles, California
April 25, 2015 11:18 pm
We spotted this beetle in Griffith Park, California. Can you tell us what it is?
Signature: Catherine Rhodes

Dear Catherine,
You have submitted an image of a Bordered Plant Bug, Largus californicus, a true bug, not a beetle.  According to BugGuide, they feed on:  “Mostly plants (flowers, leaves, fruit) from a range of families, with a preference for Lupines. L. californicus is not considered a “pest species” of economic importance.”

Dear Daniel,
Thank you so much for identifying this little guy.  That is so interesting.  I shared with my fellow bug hiking mates too.  Terrific that you do this!  Catherine

You are most welcome.  Though we have an international following, we are a local resource for you in Los Angeles.  We can see the Griffith Observatory from our offices in quaint Mount Washington in the hills of Northeast Los Angeles.

Letter 8 – Bordered Plant Bug

Subject: 2 bugs to identify
Location: Petaluma, CA
February 7, 2017 11:38 am
These are 2 bugs that I saw in my garden March 2016. Please identify them for me. Thank you so much!!
Signature: Sharon Risedorph

Dear Sharon,
This is a Bordered Plant Bug in the genus Largus, most likely Largus californicus.  According to BugGuide, they feed on:  “Mostly plants (flowers, leaves, fruit) from a range of families, with a preference for Lupines. L. californicus is not considered a “pest species” of economic importance.”  Your other insect looks like an Earwig.

Letter 9 – Bordered Plant Bug Nymphs

Coleoptera on Asclepias subverticillata
Location: Socorro County, NM
September 26, 2011 2:56 pm
Hi!
Just discovered this site; very awesome. Here’s a picture of some beetles on a Horsetail Milkweed (Asclepias subverticillata). This was in Socorro County, New Mexico, on September 16th. Just wondering what they were…
Signature: JB

Dear JB,
These are not beetles.  They are Bordered Plant Bug nymphs in the genus Largus based on this photo posted to BugGuide.  We were not aware that Bordered Plant Bugs fed on milkweed.

Letter 10 – Bordered Plant Bugs

I think it’s a beetle
But there are so many of them (See Haldane) that I really cant search through all your pix, especially because maybe they aren’t beetles. These are on what I think is an Angelica on the Mendocino Headlands in California, but I’ve seen the same guys on my wooden back fence.
Joe Hearst

Hi Joe,
These are Bordered Plant Bugs in the family Largidae, most likely the species Largus californicus. They are TRue Bugs, not beetles.

Letter 11 – Bordered Plant Bugs in large numbers

Subject:  Mystery bug in great numbers
Geographic location of the bug:  Houston, TX
Date: 10/21/2018
Time: 02:12 PM EDT
Your letter to the bugman:  These mystery bugs have been found in great numbers in our backyard and behind our fence in a wetland. They don’t fly but crawl all over the place and only appeared after Hurricane Harvey flooded our whole area very badly for an extended time.

The chickens won’t eat them at all, unfortunately. I can’t find them anywhere on the web. Not sure if we should try to eradicate them or if they are harmless.
How you want your letter signed:  KK Rush

Dear KK Rush,
These appear to be Bordered Plant Bugs, Largus bipustulatus, which are pictured on BugGuide.  According to BugGuide, they are:  “ground-dwelling or associated with the vegetative parts of forbs, shrubs and trees.”

Thank you so much! I swear I dug around all through the ‘net.
I sure wish the chickens would eat them.

Letter 12 – Bug in genus Largus

bug pic
Hello, I was hoping you could help me identify this insect. I was thinking it was some kind of weevil. What do you think?
Roberta deJoya

Hi Roberta,
We at first thought this was a Boxelder Bug, but Eric Eaton corrected us: This ” is actually a species of Largus, family Largidae:-) Bigger than your average boxelder bug, too.”

Letter 13 – BUG OF THE MONTH FEBRUARY 2009: Bordered Plant Bug

Moved Into House in Arizona, these bugs are everywhere outside
Fri, Jan 30, 2009 at 9:41 PM
I moved into a house in Peoria, Arizona. Its consider farm land out here, there are houses all around and a farm across our street. I have noticed these bugs everywhere outside. We have a shrub in the back and on the side of the house and they seem to be coming from there.
Thank You! Sara
Peoria, Az

Long, black with red perimeter on abdomen
Sat, Jan 31, 2009 at 11:07 AM
Around my house I see this insect all the time, but have no idea what it is. They are usually about 1 inch long, 1/4 inch wide, and black. But on their backs there is a perimeter (circumference?) of bright red-orange, in a thin, sharp line, all the way around.

They look very similar to the one in the image provided, except that the red-orange coloration is only around the perimeter of its back, not toward the middle, and it extends all the way around the end.
Thanks,
Kelli Welch
Vernon Parish, Louisiana, USA

Dear Sara and Kelli,
Sara has provided an image of a Bordered Plant Bug in the genus Largus. The photo is blurry, and there are many similar looking species in the genus. We believe the most likely candidate is Largus succinctus.

According to BugGuide: “Identification A large, dark bug, black or dark yellow-brown. Orange-red to orange-yellow border to abdomen margins of corium. Base fo femora also this same color. Largus cinctus is a closely-related species of the western United States. Taxonomy, and thus range, of these species not quite clear. (1)
Range Eastern, central, and southwestern United States: New York south to Florida, west to Colorado, Arizona.”

Kelli provided an image of a Box Elder Bug and the two are similar in appearance, but the Bordered Plant Bug fits Kelli’s verbal description. Since we got both of your letters in rapid succession, and it is time to select a Bug of the Month for February, we have chosen the Bordered Plant Bug.

According to Charles Hogue, who writes about the Largus cinctus californicus in his book Insects of the Los Angeles Basin: “This bug is conspicuous at times because of its habit of congregating in very large numbers on certain plants, especially herbaceous weedy shrubs.”

We are also including a better focused image of a Bordered Plant Bug sent in by Beatrix in March 2007.

Letter 14 – Mating Bordered Plant Bugs

Subject: Mystery bug ID
Location: SW Washington, Pacific County
May 26, 2016 1:57 am
These bugs showed up in our area last year for the first time. It has been suggested that they are box elder bugs, but they do not look like photos of box elder bugs. Can you help ID them?
Signature: valleygirl

Dear valleygirl,
These are Bordered Plant Bugs in the genus Largus, and considering your location, we are relatively confident they are Largus cinctus, a west coast species.  You may refer to BugGuide for additional images of Bordered Plant Bugs.

Letter 15 – Mating Bordered Plant Bugs

Subject: Unidentified beetles
Location: San Angelo, TX
May 29, 2017 8:57 am
Here are two unidentified beetles captured in an intimate moment on a fence in West Texas.
Exact location is in the photo metadata. Picture taken on 29 May 17.
Signature: Matt in San Angelo, TX

Dear Matt,
These are NOT beetles.  They are mating Bordered Plant Bugs in the genus Largus.  According to BugGuide:  “genus under revision.”

Letter 16 – Mating Yellow Bordered Flower Buprestids

Subject: Bug Love
Location: Salado Creek Greenway Trail San Antonio TX
October 6, 2012 8:31 am
A couple of Yellow bordered Flower Buprestids making out on an Engelmans Daisy
Acmaeodera flavomartinata according to my Bug Guide. Had never seen this flower beetle before.
Signature: drequador

Dear drequador,
Thanks so much for sending us your photos of mating Yellow Bordered Flower Buprestids as well as for identifying them for us.  According to BugGuide:  “Adults common on flwrs of Asteraceae” which your photograph supports, and they range from “Central and west Texas / south to Brazil.” 

Letter 17 – Metamorphosis of a Bordered Plant Bug

Big red bugs crawl out of tiny blue/black bugs!
Location: Douglas, southeast Arizona
September 23, 2011 2:12 pm
Howdy, I’ve gotten lots of rolling eyes, and shouts of ”that’s impossible!” when I try to tell people about these bugs. Long story short: maybe 2 years ago, I was taking photos of this group of tiny, shiny-bodied blue/black bugs that had been crawling on my fence.

I noticed they were slowing down and eventually came to a stop, in different places. Next thing I knew, this red head and body starting coming out of the body of one of the tiny bug!! Could not believe what I was seeing! The size difference, and the fact that the tiny bugs were mobile just a few minutes earlier, creeped me out.

So, of course, I got off a few shots…have absolutely no idea why I didn’t take more. I know a couple came out blurry.

I’ve seen these tiny bugs this year in my garden, but they disappeared before I could collect some to see if they would pull an ”Alien” for me and my camera this time:)

I didn’t know what size the pics should be…they were sent in jpeg; let me know if that needs changing. I hope this is a really rare, but known, sight so I can know I was truly seeing what I thought I was seeing. Thanks! Love your site!
Signature: Lori – Arizona

Hi Lori,
What you witnessed is amazing, but not at all unusual or rare.  You witnessed insect metamorphosis.  We believe the blue-black bugs are immature Bordered Plant Bugs in the genus Largus, a conclusion we reached upon comparing your photo to this image on BugGuide. 

Often when a true bug molts, the newly emerged insect is a reddish color, but that will soon darken as the exoskeleton hardens.

Letter 18 – Molting Hemipteran: Bordered Plant Bug???

Hi, I live in Scottsdale Arizona and I have had some little black beetle bugs living on my porch post in the back yard for about a week, they stared little and solid black, developed a red heart looking spot on their back, and have now malted their black exoskeleton and replaced it with a pink one.

I assume the pink is new skin exoskeleton and will turn black. Very strange little critters, is there anything you can tell me about them. Thanks,
Roger

Hi Roger,
This is not a beetle, but a True Bug or Hemipteran. We believe it is an immature Bordered Plant Bug in the genus Largus. BugGuide has a very similar image.

Letter 19 – Possibly Bordered Plant Bug Nymphs

Subject: Beetle
Location: S. Calif. Mojave Desert, sandy wash, Pinon Juniper woodland
July 27, 2013 10:40 pm
This beetle was on a Purshia glandulosa plant. (Antelope Bitterbrush) in the Mojave Desert–in Pinon Juniper woodland. There were many and they hid from me. I found a cluster of them on a broken branch probably utilizing the protection, moisture or sap of the broken limb.

They were very shiny, with a blackish/bluish tinge to them. Very beautiful, they captivated my attention. There was also a tiny red one amongst them, seen to the lower /middle portion of photo.

There was only one plant that I noticed them on. All other purshia in the area were clean. I found a straggler on a buckwheat but that was it.
Signature: Wendy

Hi Wendy,
These are not beetles.  They are True Bugs in the suborder Heteroptera.  We wish your photo had a better view of the larger individual which does not yet appear to have wings. 

We are not certain, but we believe these are Bordered Plant Bug nymphs in the genus Largus.  They look very similar to this image posted to BugGuide. 

Your individuals lack the red marking that is prominent in most Largus nymphs.  Perhaps desert dwellers lack the markings.  See BugGuide for more information on the genus Largus.