Milkweed bugs and boxelder bugs are often mistaken for each other due to their similarities in appearance.
Both insects boast black bodies adorned with red or orange markings, and they are commonly seen in North American gardens.
Understanding the differences between these two bugs is crucial for proper identification and, if necessary, appropriate control measures.
Milkweed bugs, belonging to the Lygaeus genus, primarily feed on milkweed plants and their seeds.
They display a heart-shaped black patch on their back along with two other black patches on either side. They are relatively smaller, usually about ½ inch long.
Boxelder bugs, on the other hand, belong to the Rhopalidae family and are identified by their three longitudinal red stripes on the pronotum.
They feed on boxelder trees and occasionally other maple tree species instead.
Although both milkweed bugs and boxelder bugs are primarily considered nuisance insects rather than harmful pests, it’s essential for gardeners and homeowners to distinguish between the two.
Gaining an understanding of their differences and respective impacts on plants can help guide any necessary control measures and prevent potential future issues.
Milkweed Bug vs Boxelder Bug: Meet the Bugs
Milkweed Bug Overview
- Orange to reddish-orange in color
- Have a black band across their back
- ¾” long as adults
These bugs undergo a life cycle that includes eggs, nymphs, and adults. They feed on milkweed, particularly the seeds. Some key features of milkweed bug nymphs include:
- Orange body
- Black legs
- Black antennae
- Black wingpads that lengthen with age
- Small black spots on the abdomen as they mature
Milkweed bugs are not major pests and do not bite or carry diseases.
Boxelder Bug Overview
- ½” long as adults
- Black body
- Orange or red markings
- Three stripes on the thorax
Like milkweed bugs, boxelder bugs also have a life cycle involving eggs, nymphs, and adults. Nymphs can be identified by their:
- Smaller size compared to adults
- Red abdominal segments
- Wing buds
Boxelder bugs feed on tree sap and can be a nuisance in the fall when they enter homes seeking warmth.
|Orange to reddish-orange
|Black band across back
|Orange or red
|Nymph Body Color
|Black and red
|Boxelder trees, other maples, ash trees
|Not major pests
Milkweed Bug vs Boxelder Bug: Habitat and Food Sources
Milkweed Bug Habitat
Milkweed bugs, including Oncopeltus fasciatus, primarily inhabit milkweed plants in gardens and fields. They are commonly found feeding on milkweed seeds and nectar, as well as:
- Seed pods
- Monarch caterpillars
- Milkweed tussock moth larvae
Apart from milkweed plants, they also mate and lay eggs around these food sources.
Boxelder Bug Habitat
Boxelder bugs, part of the Hemiptera order (true bugs), typically dwell around box elder, maple, and ash trees.
They feed on the sap of leaves, tender twigs, and developing seeds, while sometimes attacking the fruits of raspberry and strawberry plants.
Boxelder bugs are often found in:
- Fruit trees
- Crevices and cracks of homes (seeking shelter during colder months)
Although adult boxelder bugs can be a harmless nuisance to homeowners, many people find them annoying and use pesticide solutions to control their populations.
Key features of Habitat and Food Sources:
- Milkweed bugs: milkweed plants, seeds, various insects
- Boxelder bugs: box elder, maple, and ash trees, sap feeds
|Gardens, milkweed plants
|Gardens, trees (maple, ash, box elder)
|Seeds, nectar, insects
|Tree sap, fruit
|Moderate (in large numbers)
|Harmless to humans
|Harmless to humans
|No specific measures
Keep in mind that while both bugs are generally harmless, they might become a nuisance depending on their population size in a given area.
Milkweed Bug vs Boxelder Bug: Physical Characteristics and Behavior
Milkweed Bug Characteristics
Milkweed bugs consist of two species: large milkweed bugs (Oncopeltus fasciatus) and small milkweed bugs (Lygaeus kalmii). Both species have unique features:
- Large milkweed bug:
- Adult size: ¾” long
- Color: Orange to reddish-orange with a black band across their back.
- Habitat: commonly found on milkweed, feeding on seeds.
- Small milkweed bug:
- Adult size: Up to ½” long
- Color: Black with a large red X-shape on the back, white margins on wings, and a red band on the pronotum.
- Habitat: Also found on milkweed, similar feeding habits to large milkweed bugs.
Boxelder Bug Characteristics
Boxelder bugs (Boisea trivittata) have distinct features that set them apart from the milkweed bugs:
- Boxelder bug:
- Adult size: ½” long
- Color: Dark gray to black with three red stripes on the thorax, outlined wings in red, and red eyes.
- Habitat: Commonly found on boxelder trees and occasionally on other related maple species.
- Both milkweed bugs and boxelder bugs exhibit diurnal activity, meaning they are active during daylight hours.
- Some similarities in behavior include mating patterns, where both milkweed and boxelder bugs often gather in large groups on plants or trees to mate.
- Both types of bugs have incomplete metamorphosis, meaning they have nymph stages, which are followed by molting until they become adults.
Important differences include their preferred hosts: milkweed bugs often feed on milkweeds (such as the monarch butterflies), whereas boxelder bugs feed primarily on boxelder tree seeds and occasionally on maple trees.
|Oncopeltus fasciatus, Lygaeus kalmii
|¾” (large), ½” (small)
|Orange/red with a black pattern
|Dark gray to black with red markings
|Boxelder trees, sometimes maple trees
Milkweed Bug vs Boxelder Bug: Impact on Plants
Milkweed bugs, as their name suggests, primarily feed on milkweed plants. Their primary diet consists of the seeds of the milkweed, which they pierce with their proboscis to extract the nutrients.
While this feeding doesn’t typically kill the plant, it can reduce the number of seeds the plant produces and, over time, can weaken the plant.
This is especially noticeable in gardens where milkweed is cultivated for the benefit of monarch butterflies, as a significant reduction in seeds can impact the availability of new plants in subsequent seasons.
Boxelder bugs primarily feed on boxelder trees, specifically on the sap from its leaves, tender twigs, and developing seeds.
While they do not cause significant harm to the trees, their feeding can sometimes lead to cosmetic damage, leaving behind yellowish spots on leaves where they’ve fed.
In gardens or landscapes where aesthetics are a priority, this can be a concern. Additionally, their tendency to congregate in large numbers can be alarming, even if the actual damage to the tree is minimal.
Milkweed Bug vs Boxelder Bug: Dealing with Infestations
Managing Milkweed Bugs
Milkweed bugs, both large and small, are commonly found on milkweed plants, particularly feeding on seeds1. While some gardeners may not mind their presence, an infestation can be concerning.
- Adult stage: Monitor the adult bugs by routinely checking the milkweed plants.
- Removal: Manually remove any visible bugs, or use a garden hose to spray them off the plant.
- Pesticides: If necessary, use a selective pesticide or insecticidal soap to target the milkweed bug population. Be cautious, as it may harm other beneficial insects.
- Milkweed assassin bugs: These predatory insects can help control milkweed bug populations2.
Managing Boxelder Bugs
- Prevention: Seal cracks and gaps around windows, doors, and siding to prevent entry into the home4.
- Screens: Install screens on windows and vents to keep boxelder bugs out.
- Leaf litter: Remove leaf litter and other debris around the home, as these serve as harborage sites.
- Pesticides: Apply appropriate pesticide treatments to the infested area, targeting the bugs’ hiding spots. Consider consulting an exterminator for severe infestations.
Boxelder Bug Nymphs
|Feed on milkweed plants/seeds
|Feed on boxelder trees
|Reddish-orange with black bands
|Three longitudinal red stripes on pronotum5
|Can damage milkweed gardens
|Are major nuisance in and around homes
Milkweed bugs and boxelder bugs, while similar in appearance, have distinct characteristics and behaviors that set them apart.
From their preferred habitats to their unique markings, understanding these differences is essential for proper identification.
While both bugs play a role in their respective ecosystems, it’s crucial for homeowners and gardeners to recognize and manage them appropriately to prevent potential nuisances or damage to plants.
Over the years, our website, whatsthatbug.com has received hundreds of letters and some interesting images asking us about milkweed and boxelder bugs. Scroll down to have a look at some of them.
Letter 1 – Endorsement: Soap against Box Elder Bugs really works!!!!!
Box Elder Bug Great, great site! Although I’m entirely creeped out and won’t sleep for a week, I did identify the giant swarm of box elder bugs covering my back yard near – what else? – the box elder and maple trees.
They’ve been there for several years, and when I read they could come in the house, it was time for them to go. Many many thanks to Debbie Fenclau for the environment- and pet-friendly solution of spraying them with laundry soap solution.
Worked like a charm and as much as I hate to see things die, that they did right in front of my eyes. And, although I’ll be silently screaming in horror, I will leave the house centipedes be now so they can eat worse things.
I have already forwarded your site to a number of friends, including my sister who just moved to California and will have a whole new bunch of bugs to make friends with. The information you provide is wonderful, and your site will be the first place I go to ID new bugs.
Dearborn Heights, MI
p.s. found your site via Google-ing “identifying insects in Michigan”
Letter 2 – First Boxelder Bug photo of the season
Red and black beetle?
Two days ago, hundreds (thousands?) of these red and black bugs appeared in my Atlanta backyard. I don’t think I’ve ever seen them before. What are they?
These are not beetles. They are Boxelder Bugs and this is the first photo we have received this season.
We get numerous reports in the fall from people who have huge aggregations of Boxelder Bugs on their maple trees, on the sunny sides of their homes, and occasionally when it gets cold, inside their homes.
Winged adults alse aggregate with the immature nymphs you have pictured in your photo.
Letter 3 – Fanmail
Box Elder help
December 12, 2010 7:21 pm
First, I want to thank you for this site. I’m using it in a mental health capacity to help with my bug phobia. It’s really helpful to look at the pictures and descriptions and learn about individual insects and creatures.
It helps to demystify them and I’m finding myself much less scared of harmless bugs I see now.
Secondly, I live in Wisconsin where it is bitter cold and blowing snow right now. I’ve noticed a box elder bug is taking refuge in my apartment. I know he or she is harmless, so am using this as an opportunity to calm my fears and let this creature exist in my home with me instead of forcing it outside where it will surely freeze to death.
What I’m wondering is if there is any reason I shouldn’t continue to let it hang out in my home, and also how long it might survive in here as opposed to outside. Thanks a lot!
Thanks so much for your kind letter. Our readers who are plagued by Boxelder Bug home invasions will be amused with your solitary visitor.
Boxelder Bugs often seek shelter indoors in prodigious when cold weather arrives, and they will pass the winter in comfort while waiting for spring to arrive. The Boxelder Bug will not harm your home and there is no reason why you shouldn’t allow it to remain.
Letter 4 – Home Security System does not keep out Boxelder Bugs
Location: Long Island NY
March 5, 2011 11:52 am
These bugs are under our vinyl siding and now that it’s winter, they are getting into the house some how. I just want to make sure they are not wood eaters of some kind. We have had problems with termites in the past.
Signature: Katherine R
This is a Boxelder Bug and it is a benign insect, though since they are in the habit of entering homes to hibernate, often in great numbers, they are considered a nuisance. We find your photo of this intruder on the home security control pad quite amusing.
Letter 5 – Eastern Boxelder Bug nymphs on Milkweed?????
Subject: Bugs on Butterlfy weed plant
Geographic location of the bug: Annapolis, MD USA
Time: 11:31 AM EDT
Your letter to the bugman: I have seen orange and blank milkweed bugs before, but these are bright pink and blue.
How you want your letter signed: zelda
Thank you so much for replying. Yes, there is a maple tree not too far away, but not directly near this patch. So interesting – I will keep watching. Love the web site; I just found it!
We would love to see images of the winged adults.
Ok, I’ll be on the lookout – about how long does maturation take?
We suspect you should have adults within a month.