Milkweed Bug vs Boxelder Bug: Anatomy of a Comparative Study

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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.

Milkweed Bug vs Boxelder Bug

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

Milkweed bugs are colorful insects that can be found on milkweed plants. They are:

  • 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

Boxelder bugs are common pests often found on boxelder trees, as well as other maples and ash trees in North America. Distinct features include:

  • 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
Eastern Boxelder Bug

Boxelder bugs feed on tree sap and can be a nuisance in the fall when they enter homes seeking warmth.

Comparison Table

Feature Milkweed Bug Boxelder Bug
Adult Size ¾” long ½” long
Body Color Orange to reddish-orange Black
Markings Black band across back Orange or red
Nymph Body Color Orange Black and red
Preferred Habitat Milkweed plants Boxelder trees, other maples, ash trees
Pest Status Not major pests Nuisance pests
Bite Risk No No
Disease Transmission No No

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
  • Aphids

Apart from milkweed plants, they also mate and lay eggs around these food sources.

Large Milkweed Bug with nymphs

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:

  • Gardens
  • Fruit trees
  • Crevices and cracks of homes (seeking shelter during colder months)
Eastern Boxelder Bug

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

Comparison Table

Feature Milkweed Bug Boxelder Bug
Habitat Gardens, milkweed plants Gardens, trees (maple, ash, box elder)
Food Source Seeds, nectar, insects Tree sap, fruit
Nuisance Level Low Moderate (in large numbers)
Harmfulness Harmless to humans Harmless to humans
Control Measures No specific measures Pesticide solutions

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.
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.
Democrat Bugs

Behavior Patterns

  • 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.

Comparison Table:

Bug Milkweed Bug Boxelder Bug
Species Oncopeltus fasciatus, Lygaeus kalmii Boisea trivittata
Adult Size ¾” (large), ½” (small) ½”
Color Orange/red with a black pattern Dark gray to black with red markings
Primary Habitat Milkweed plants Boxelder trees, sometimes maple trees

Milkweed Bug vs Boxelder Bug: Impact on Plants

Milkweed Bugs

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.

Large Milkweed Bugs: Adults and Nymphs

Boxelder Bugs

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.

Aggregation of Eastern Boxelder Bugs

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.
Immature Large Milkweed Bugs

Managing Boxelder Bugs

Boxelder bugs are another common pest that can be mistaken for milkweed bugs2. They can cause a nuisance around homes by congregating on exterior walls and making their way inside3.

  • 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

Milkweed Bugs Boxelder Bugs
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.


  1. More than monarchs – What are those bugs on my milkweed?
  2. Common Milkweed Insects – Wisconsin Horticulture 2
  3. Why are all these bugs appearing on the side or inside of my home?
  4. Identifying Common Household Insect Pests
  5. Nuisance insects | UMN Extension


  • Bugman

    Bugman aka Daniel Marlos has been identifying bugs since 1999. 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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Tags: Boxelder Bug

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